# Does the dust around SMBH's protect habitable planets from jets?

The supermassive black hole in the Milky Way is covered by dust as seen from here. Is it common that SMBH's are covered in dust in their galactic disks? Would that dust absorb and disperse a jet from an active galactic nucleus, so that the atmospheres of Earth like planets would be protected?

AGN jets build bubbles perpendicular to the galactic plane, but the jet could be oriented in any direction, right? The bubbles are shaped by general stellar winds from the disk, redirecting the jet streamed material towards the galactic poles, if I get that rigt.

Most galaxies have enough dust to hide their cores from investigation in visible light. But the jet from an AGN is composed of large amounts of relativistic particles, and is easily powerful enough to clear any dust out of its path. We see in M87 a jet punch 5000 light years from an active nucleus.

The dust that hides Sagittarius A* is not localised around the black hole, it is spread through the bulge, bar and disk. You would not want to be anywhere near an active galactic nucleus. Large amounts of radiation are produced by the accretion disc surrounding the black hole. Distance and dust may provide some protection to a star orbiting an active galaxy at the distance of the sun from Sag A*, but not if the star is directly in the jet.

## Why aren’t galaxies spherical?

I was following with much interest the news about S2 and its potential to provide more evidence (or potentially disprove) Einstein’s Theory of General Relativity, and I got onto a tangent and ended up wondering, if every galaxy has a black hole in the middle, why do most galaxies (at least the conceptual images of galaxies) look like discs and not like spheres? A followup question would be why don’t any of the planets follow an orbit pattern perpendicular to the rest of the “normal” orbits. This is my first post, so sorry for any violated rules!

The answers in this thread so far are almost entirely incorrect, so I'll contribute one:

First, the origins of galaxy morphology is an active and far from settled field of study, with numerous key factors that affect a galaxy's morphology:

The presence of gas and dust, which provides fuel for star formation, causes "clumpiness" in galaxy disks, and tends to circularize star orbits and cause them to settle onto a single plane.

The presence of an active galactic nucleus (AGN), which is powered by the central supermassive black hole (SMBH). An accreting black hole is as close to a pure mass --> energy conversion device as can be found in nature, and a SMBH with a mass millions to billions of times that of the Sun can dump an incredible amount of energy into the surrounding environment, shutting down or regulating star formation and blowing out gas and dust.

The presence of star formation, which consumes hydrogen gas both from the galaxy and its environment and converts it to heavier elements (dust). This produces both stellar winds that affect the immediate environment around star formation, and supernovae (when the largest stars run out of fuel) that can inject massive amounts of energy into the large-scale environment and "puff up" the disk of a galaxy.

Dark matter, which is responsible for the overall dynamics of the galaxy, especially the faster-than-expected motions of stars in disks.

Mergers, which destabilize galaxies and cause them to either become more dissipated in the case of minor interactions, or to trigger star formation and AGN activity in the case of major interactions.

Having enumerated these factors, the broad picture is that disk galaxies formed when gas and dust in the early universe settled onto roughly circular, co-planar orbits. These gas-rich systems underwent star formation over time that caused a slow morphological evolution to "red and dead" dusty galaxies without much spiral structure. At the same time, many galaxies merged with each other. This merging process randomized the orbits of their stars, creating a spherical morphology, and triggered both massive star formation and AGN activity that consumed their gas and blew out their dust, creating the massive elliptical galaxies that we see in the local universe.

One factor that does not have an effect on the morphology of the galaxy is the gravity from the central SMBH. Stars, gas, and dust do not orbit around the central SMBH: it orbits around their mutual center of gravity, which the SMBH just happens to reside at (for symmetrical galaxies at least). The gravitational sphere of influence of the SMBH is much, much too small to affect the motions of stars, gas, and dust throughout the galaxy. The effect of the SMBH is, as I stated above, to provide an engine for AGN activity, which does affect the large-scale structure via AGN "feedback" (radiation and jets from the AGN that impact upon the large-scale environment).

## Blanets? They’re Planets That Form Around Black Holes

Some things about planets are constants. Most of them form around stars and stay in their orbit. Some get cut loose for a variety of reasons and become rogues. A few get too close to black holes and get sucked into the abyss. Then there’s blanets. What are blanets? Get ready to meet the bravest planets in the universe.

“In Wada, Tsukamoto, and Kokubo (2019), we proposed for the first time that a new class of planets, blanets (i.e., black hole planets), can be formed around supermassive black holes (SMBHs) in the galactic center. Here, we investigate the dust coagulation processes and physical conditions of the blanet formation outside the snowline in more detail, especially considering the effect of the radial advection of the dust aggregates.”

Keiichi Wada, Yusuke Tsukamoto and Eiichiro Kokubo are Japanese space researchers and university professors who have updated their 2019 paper on stuff that is seen around supermassive black holes with a new study submitted to The Astrophysical Journal detailing what they’re calling a new class of exoplanets – the blanet. In particular, they have been studying the supermassive black holes found at the center of most galaxies which are usually very active, with a disc of accretion dust and gas circling around it and avoiding consumption in a game of supermassive cat and mouse. While they originally thought planets in these accretion discs had been rogue exoplanets or planets orbiting stars captured by the black hole, this new study proposes that they actually form in the disc in somewhat the same way planets form around young stars.

“Our results suggest that blanets could be formed around relatively low-luminosity active galactic nuclei during their lifetime (100 million years). The gaseous envelope of a blanet should be negligibly small compared with the blanet mass. Therefore, the system of blanets are extraordinarily different from the standard Earth-type planets in the exoplanet systems.”

By “extraordinarily different,” the team means they grow much faster into much, much more massive than star-based planets. While the growth of planets in star-orbiting accretion discs are slowed by collisions, the black hole accretion discs have a lower viscosity – i.e., less traffic – that reduces the risk of collision. Because the viscosity is even lower at the outer edges of the disc, planets out there can grow quickly to masses that are 20 to 3,000 Earth masses, reaching what is considered the upper limit of planet size but not quite large enough to become a small star instead.

“The dynamical stability of such a system around a SMBH (supermassive black hole) may be an interesting subject for future studies.”

As you may have expected, these blanets can’t be seen – the study was done using models of supermassive black hole behavior. The team thinks all of this is “interesting” enough for future studies, provided they can find the grant money.

Could life exist on one of these blanets? A better question is: Why would life want to live so close to a supermassive black hole?

## Active Galactic Nuclei and Star Formation

The galaxy UGC 5101 contains an active nucleus (AGN), a compact core that emits copious radiation and possible stimulates star formation. In this Hubble image, the tidal tail at the left suggests that the galaxy is actually a merging pair of galaxies. Astronomers studying how AGN influence their host galaxy's development have concluded that both grow together.

Most galaxies host a supermassive black hole (SMBH) at their nucleus (a supermassive black hole is one whose mass exceeds a million solar-masses.) A key unresolved issue in galaxy formation and evolution is the role these SMBHs play in shaping their galaxies. Most astronomers agree that there must be a strong connection because of the observed correlations between a SMBH's mass and its galaxy's luminosity, stellar mass, and the stellar motions in the galaxy. These correlations apply both in local galaxies and those at earlier cosmic epochs. But despite progress in studying SMBHs, how they effect their hosts still not understood. In some suggested scenarios the SMBH suppresses star formation in the galaxy by expelling material. In others, like the merger scenario, the effect is the opposite: the SMBH boosts star formation by helping stir up the interstellar medium. Computer simulations have been undertaken to try to settle these differences, and they tend to show that cold gas flowing in from the intergalactic medium can feed both SMBH and galaxy growth.

Star formation is one of the principle markers of galaxy growth. Observations of galaxies have tried to measure the star formation by correlating the formation rate with the intrinsic luminosity (star formation heats the dust whose infrared emission can dominate the luminosity). However, the emission from the region around a supermassive black hole that is actively accreting, an active galactic nucleus (AGN), can easily be confused with the emission from star formation. X-rays or the emission of highly excited ions can be used to determine the AGN contributions independently, but these measures may be complicated by intervening dust extinction or other effects. Furthermore there is evidence that in small or less luminous galaxies, or in those at earlier cosmic epochs, other factors like element abundances strongly influenced the galaxy's development.

CfA astronomer Belinda Wilkes and Joanna Kuraszkiewicz and five colleagues examined 323 galaxies known to host AGN from their strong X-ray emission (as measured by the XMM-Newton telescope) and also to have active star formation underway as determined by their far infrared emission (as measured with the Herschel Space Telescope). The galaxies are all at distances such that their light has been traveling from between about two to eleven billion years. Their statistical analysis of the sample finds that on average the AGN contributes about 20% to the infrared luminosity although it can sometimes be as much as >90%. They reach the important conclusions that there is no evidence (at least in this set of objects) for a strong correlation between the two or that AGN quench the star formation. In fact, it appears that both grow together.

"Is There a Relationship Between Agn and Star Formation in Ir-Bright Agns?" Y. Sophia Dai, Belinda J. Wilkes, Jacqueline Bergeron, Joanna Kuraszkiewicz, Alain Omont, Adam Atanas, and Harry I. Teplitz, MNRAS 478, 4238, 2018.

## There’s a Funny Cloud on Mars, Perched Right at the Arsia Mons Volcano. Don’t Get Too Excited, Though, it’s not an Eruption

The ESA’s Mars Express orbiter has spotted a funny cloud on Mars, right near the Arsia Mons Volcano. At first glance it looks like a plume coming out of the volcano. But it’s formation is not related to any internal activity in this long-dead volcano. It’s a cloud of water ice known as an orographic or lee cloud.

The cloud isn’t linked to any volcanic activity, but its formation is associated with the form and altitude of Arsia Mons. Arsia Mons is a dormant volcano, with scientists putting its last eruptive activity at 10 mya. This isn’t the first time this type of cloud has been seen hovering around Arsia Mons.

## Contents

An estimate of the range of distances from the Sun allowing the existence of liquid water appears in Newton's Principia (Book III, Section 1, corol. 4). [24] [ clarification needed ]

The concept of a circumstellar habitable zone was first introduced [25] in 1913, by Edward Maunder in his book "Are The Planets Inhabited?". The relevant quotations are given in . [26] The concept was later discussed in 1953 by Hubertus Strughold, who in his treatise The Green and the Red Planet: A Physiological Study of the Possibility of Life on Mars, coined the term "ecosphere" and referred to various "zones" in which life could emerge. [7] [27] In the same year, Harlow Shapley wrote "Liquid Water Belt", which described the same concept in further scientific detail. Both works stressed the importance of liquid water to life. [28] Su-Shu Huang, an American astrophysicist, first introduced the term "habitable zone" in 1959 to refer to the area around a star where liquid water could exist on a sufficiently large body, and was the first to introduce it in the context of planetary habitability and extraterrestrial life. [29] [30] A major early contributor to habitable zone concept, Huang argued in 1960 that circumstellar habitable zones, and by extension extraterrestrial life, would be uncommon in multiple star systems, given the gravitational instabilities of those systems. [31]

The concept of habitable zones was further developed in 1964 by Stephen H. Dole in his book Habitable Planets for Man, in which he discussed the concept of circumstellar habitable zone as well as various other determinants of planetary habitability, eventually estimating the number of habitable planets in the Milky Way to be about 600 million. [2] At the same time, science-fiction author Isaac Asimov introduced the concept of a circumstellar habitable zone to the general public through his various explorations of space colonization. [32] The term "Goldilocks zone" emerged in the 1970s, referencing specifically a region around a star whose temperature is "just right" for water to be present in the liquid phase. [33] In 1993, astronomer James Kasting introduced the term "circumstellar habitable zone" to refer more precisely to the region then (and still) known as the habitable zone. [29] Kasting was the first to present a detailed model for the habitable zone for exoplanets. [3] [34]

An update to habitable zone concept came in 2000, when astronomers Peter Ward and Donald Brownlee, introduced the idea of the "galactic habitable zone", which they later developed with Guillermo Gonzalez. [35] [36] The galactic habitable zone, defined as the region where life is most likely to emerge in a galaxy, encompasses those regions close enough to a galactic center that stars there are enriched with heavier elements, but not so close that star systems, planetary orbits, and the emergence of life would be frequently disrupted by the intense radiation and enormous gravitational forces commonly found at galactic centers. [35]

Subsequently, some astrobiologists propose that the concept be extended to other solvents, including dihydrogen, sulfuric acid, dinitrogen, formamide, and methane, among others, which would support hypothetical life forms that use an alternative biochemistry. [23] In 2013, further developments in habitable zone concepts were made with the proposal of a circum planetary habitable zone, also known as the "habitable edge", to encompass the region around a planet where the orbits of natural satellites would not be disrupted, and at the same time tidal heating from the planet would not cause liquid water to boil away. [37]

It has been noted that the current term of 'circumstellar habitable zone' poses confusion as the name suggests that planets within this region will possess a habitable environment. [38] [39] However, surface conditions are dependent on a host of different individual properties of that planet. [38] [39] This misunderstanding is reflected in excited reports of 'habitable planets'. [40] [41] [42] Since it is completely unknown whether conditions on these distant CHZ worlds could host life, different terminology is needed. [39] [41] [43] [44]

Whether a body is in the circumstellar habitable zone of its host star is dependent on the radius of the planet's orbit (for natural satellites, the host planet's orbit), the mass of the body itself, and the radiative flux of the host star. Given the large spread in the masses of planets within a circumstellar habitable zone, coupled with the discovery of super-Earth planets which can sustain thicker atmospheres and stronger magnetic fields than Earth, circumstellar habitable zones are now split into two separate regions—a "conservative habitable zone" in which lower-mass planets like Earth can remain habitable, complemented by a larger "extended habitable zone" in which a planet like Venus, with stronger greenhouse effects, can have the right temperature for liquid water to exist at the surface. [46]

### Solar System estimates Edit

Estimates for the habitable zone within the Solar System range from 0.38 to 10.0 astronomical units, [47] [48] [49] [50] though arriving at these estimates has been challenging for a variety of reasons. Numerous planetary mass objects orbit within, or close to, this range and as such receive sufficient sunlight to raise temperatures above the freezing point of water. However their atmospheric conditions vary substantially. The aphelion of Venus, for example, touches the inner edge of the zone and while atmospheric pressure at the surface is sufficient for liquid water, a strong greenhouse effect raises surface temperatures to 462 °C (864 °F) at which water can only exist as vapour. [51] The entire orbits of the Moon, [52] Mars, [53] and numerous asteroids also lie within various estimates of the habitable zone. Only at Mars' lowest elevations (less than 30% of the planet's surface) is atmospheric pressure and temperature sufficient for water to, if present, exist in liquid form for short periods. [54] At Hellas Basin, for example, atmospheric pressures can reach 1,115 Pa and temperatures above zero Celsius (about the triple point for water) for 70 days in the Martian year. [54] Despite indirect evidence in the form of seasonal flows on warm Martian slopes, [55] [56] [57] [58] no confirmation has been made of the presence of liquid water there. While other objects orbit partly within this zone, including comets, Ceres [59] is the only one of planetary mass. A combination of low mass and an inability to mitigate evaporation and atmosphere loss against the solar wind make it impossible for these bodies to sustain liquid water on their surface. Despite this, studies are strongly suggestive of past liquid water on the surface of Venus, [60] Mars, [61] [62] [63] Vesta [64] and Ceres, [65] [66] suggesting a more common phenomena than previously thought. Since sustainable liquid water is thought to be essential to support complex life, most estimates, therefore, are inferred from the effect that a repositioned orbit would have on the habitability of Earth or Venus as their surface gravity allows sufficient atmosphere to be retained for several billion years.

According to extended habitable zone concept, planetary-mass objects with atmospheres capable of inducing sufficient radiative forcing could possess liquid water farther out from the Sun. Such objects could include those whose atmospheres contain a high component of greenhouse gas and terrestrial planets much more massive than Earth (super-Earth class planets), that have retained atmospheres with surface pressures of up to 100 kbar. There are no examples of such objects in the Solar System to study not enough is known about the nature of atmospheres of these kinds of extrasolar objects, and their position in the habitable zone cannot determine the net temperature effect of such atmospheres including induced albedo, anti-greenhouse or other possible heat sources.

For reference, the average distance from the Sun of some major bodies within the various estimates of the habitable zone is: Mercury, 0.39 AU Venus, 0.72 AU Earth, 1.00 AU Mars, 1.52 AU Vesta, 2.36 AU Ceres, 2.77 AU Jupiter, 5.20 AU Saturn, 9.58 AU.

Estimates of the circumstellar habitable zone boundaries of the Solar System
Inner edge (AU) Outer edge (AU) Year Notes
0.725 1.24 1964, Dole [2] Used optically thin atmospheres and fixed albedos. Places the aphelion of Venus just inside the zone.
1.005–1.008 1969, Budyko [67] Based on studies of ice albedo feedback models to determine the point at which Earth would experience global glaciation. This estimate was supported in studies by Sellers 1969 [68] and North 1975. [69]
0.92-0.96 1970, Rasool and De Bergh [70] Based on studies of Venus's atmosphere, Rasool and De Bergh concluded that this is the minimum distance at which Earth would have formed stable oceans.
0.958 1.004 1979, Hart et al. [71] Based on computer modelling and simulations of the evolution of Earth's atmospheric composition and surface temperature. This estimate has often been cited by subsequent publications.
3.0 1992, Fogg [45] Used the carbon cycle to estimate the outer edge of the circumstellar habitable zone.
0.95 1.37 1993, Kasting et al. [29] Founded the most common working definition of the habitable zone used today. Assumes that CO2 and H2O are the key greenhouse gases as they are for the Earth. Argued that the habitable zone is wide because of the carbonate–silicate cycle. Noted the cooling effect of cloud albedo. Table shows conservative limits. Optimistic limits were 0.84–1.67 AU.
2.0 2010, Spiegel et al. [72] Proposed that seasonal liquid water is possible to this limit when combining high obliquity and orbital eccentricity.
0.75 2011, Abe et al. [73] Found that land-dominated "desert planets" with water at the poles could exist closer to the Sun than watery planets like Earth.
10 2011, Pierrehumbert and Gaidos [48] Terrestrial planets that accrete tens-to-thousands of bars of primordial hydrogen from the protoplanetary disc may be habitable at distances that extend as far out as 10 AU in the Solar System.
0.77–0.87 1.02–1.18 2013, Vladilo et al. [74] Inner edge of circumstellar habitable zone is closer and outer edge is farther for higher atmospheric pressures determined minimum atmospheric pressure required to be 15 mbar.
0.99 1.70 2013, Kopparapu et al. [4] [75] Revised estimates of the Kasting et al. (1993) formulation using updated moist greenhouse and water loss algorithms. According to this measure Earth is at the inner edge of the HZ and close to, but just outside, the moist greenhouse limit. As with Kasting et al. (1993), this applies to an Earth-like planet where the "water loss" (moist greenhouse) limit, at the inner edge of the habitable zone, is where the temperature has reached around 60 Celsius and is high enough, right up into the troposphere, that the atmosphere has become fully saturated with water vapour. Once the stratosphere becomes wet, water vapour photolysis releases hydrogen into space. At this point cloud feedback cooling does not increase significantly with further warming. The "maximum greenhouse" limit, at the outer edge, is where a CO
2 dominated atmosphere, of around 8 bars, has produced the maximum amount of greenhouse warming, and further increases in CO
2 will not create enough warming to prevent CO
2 catastrophically freezing out of the atmosphere. Optimistic limits were 0.97–1.70 AU. This definition does not take into account possible radiative warming by CO
2 clouds.
0.38 2013, Zsom et al.
[47]
Estimate based on various possible combinations of atmospheric composition, pressure and relative humidity of the planet's atmosphere.
0.95 2013, Leconte et al. [76] Using 3-D models, these authors computed an inner edge of 0.95 AU for the Solar System.
0.95 2.4 2017, Ramirez and Kaltenegger
[49]
An expansion of the classical carbon dioxide-water vapor habitable zone [29] assuming a volcanic hydrogen atmospheric concentration of 50%.
0.93–0.91 2019, Gomez-Leal et al.
[77]
Estimation of the moist greenhouse threshold by measuring the water mixing ratio in the lower stratosphere, the surface temperature, and the climate sensitivity on an Earth analog with and without ozone, using a global climate model (GCM). It shows the correlation of a water mixing ratio value of 7 g/kg, a surface temperature of about 320 K, and a peak of the climate sensitivity in both cases.
0.99 1.004 Tightest bounded estimate from above
0.38 10 Most relaxed estimate from above

### Extrasolar extrapolation Edit

Astronomers use stellar flux and the inverse-square law to extrapolate circumstellar habitable zone models created for the Solar System to other stars. For example, according to Kopparapu's habitable zone estimate, although the Solar System has a circumstellar habitable zone centered at 1.34 AU from the Sun, [4] a star with 0.25 times the luminosity of the Sun would have a habitable zone centered at 0.25 >> , or 0.5, the distance from the star, corresponding to a distance of 0.67 AU. Various complicating factors, though, including the individual characteristics of stars themselves, mean that extrasolar extrapolation of the CHZ concept is more complex.

#### Spectral types and star-system characteristics Edit

Some scientists argue that the concept of a circumstellar habitable zone is actually limited to stars in certain types of systems or of certain spectral types. Binary systems, for example, have circumstellar habitable zones that differ from those of single-star planetary systems, in addition to the orbital stability concerns inherent with a three-body configuration. [78] If the Solar System were such a binary system, the outer limits of the resulting circumstellar habitable zone could extend as far as 2.4 AU. [79] [80]

With regard to spectral types, Zoltán Balog proposes that O-type stars cannot form planets due to the photoevaporation caused by their strong ultraviolet emissions. [81] Studying ultraviolet emissions, Andrea Buccino found that only 40% of stars studied (including the Sun) had overlapping liquid water and ultraviolet habitable zones. [82] Stars smaller than the Sun, on the other hand, have distinct impediments to habitability. For example, Michael Hart proposed that only main-sequence stars of spectral class K0 or brighter could offer habitable zones, an idea which has evolved in modern times into the concept of a tidal locking radius for red dwarfs. Within this radius, which is coincidental with the red-dwarf habitable zone, it has been suggested that the volcanism caused by tidal heating could cause a "tidal Venus" planet with high temperatures and no hospitable environment to life. [83]

Others maintain that circumstellar habitable zones are more common, and that it is indeed possible for water to exist on planets orbiting cooler stars. Climate modelling from 2013 supports the idea that red dwarf stars can support planets with relatively constant temperatures over their surfaces in spite of tidal locking. [84] Astronomy professor Eric Agol argues that even white dwarfs may support a relatively brief habitable zone through planetary migration. [85] At the same time, others have written in similar support of semi-stable, temporary habitable zones around brown dwarfs. [83] Also, a habitable zone in the outer parts of stellar systems may exist during the pre-main-sequence phase of stellar evolution, especially around M-dwarfs, potentially lasting for billion-year timescales. [86]

#### Stellar evolution Edit

Circumstellar habitable zones change over time with stellar evolution. For example, hot O-type stars, which may remain on the main sequence for fewer than 10 million years, [87] would have rapidly changing habitable zones not conducive to the development of life. Red dwarf stars, on the other hand, which can live for hundreds of billions of years on the main sequence, would have planets with ample time for life to develop and evolve. [88] [89] Even while stars are on the main sequence, though, their energy output steadily increases, pushing their habitable zones farther out our Sun, for example, was 75% as bright in the Archaean as it is now, [90] and in the future, continued increases in energy output will put Earth outside the Sun's habitable zone, even before it reaches the red giant phase. [91] In order to deal with this increase in luminosity, the concept of a continuously habitable zone has been introduced. As the name suggests, the continuously habitable zone is a region around a star in which planetary-mass bodies can sustain liquid water for a given period. Like the general circumstellar habitable zone, the continuously habitable zone of a star is divided into a conservative and extended region. [91]

In red dwarf systems, gigantic stellar flares which could double a star's brightness in minutes [92] and huge starspots which can cover 20% of the star's surface area, [93] have the potential to strip an otherwise habitable planet of its atmosphere and water. [94] As with more massive stars, though, stellar evolution changes their nature and energy flux, [95] so by about 1.2 billion years of age, red dwarfs generally become sufficiently constant to allow for the development of life. [94] [96]

Once a star has evolved sufficiently to become a red giant, its circumstellar habitable zone will change dramatically from its main-sequence size. [97] For example, the Sun is expected to engulf the previously-habitable Earth as a red giant. [98] [99] However, once a red giant star reaches the horizontal branch, it achieves a new equilibrium and can sustain a new circumstellar habitable zone, which in the case of the Sun would range from 7 to 22 AU. [100] At such stage, Saturn's moon Titan would likely be habitable in Earth's temperature sense. [101] Given that this new equilibrium lasts for about 1 Gyr, and because life on Earth emerged by 0.7 Gyr from the formation of the Solar System at latest, life could conceivably develop on planetary mass objects in the habitable zone of red giants. [100] However, around such a helium-burning star, important life processes like photosynthesis could only happen around planets where the atmosphere has carbon dioxide, as by the time a solar-mass star becomes a red giant, planetary-mass bodies would have already absorbed much of their free carbon dioxide. [102] Moreover, as Ramirez and Kaltenegger (2016) [99] showed, intense stellar winds would completely remove the atmospheres of such smaller planetary bodies, rendering them uninhabitable anyway. Thus, Titan would not be habitable even after the Sun becomes a red giant. [99] Nevertheless, life need not originate during this stage of stellar evolution for it to be detected. Once the star becomes a red giant, and the habitable zone extends outward, the icy surface would melt, forming a temporary atmosphere that can be searched for signs of life that may have been thriving before the start of the red giant stage. [99]

#### Desert planets Edit

A planet's atmospheric conditions influence its ability to retain heat, so that the location of the habitable zone is also specific to each type of planet: desert planets (also known as dry planets), with very little water, will have less water vapor in the atmosphere than Earth and so have a reduced greenhouse effect, meaning that a desert planet could maintain oases of water closer to its star than Earth is to the Sun. The lack of water also means there is less ice to reflect heat into space, so the outer edge of desert-planet habitable zones is further out. [103] [104]

#### Other considerations Edit

A planet cannot have a hydrosphere—a key ingredient for the formation of carbon-based life—unless there is a source for water within its stellar system. The origin of water on Earth is still not completely understood possible sources include the result of impacts with icy bodies, outgassing, mineralization, leakage from hydrous minerals from the lithosphere, and photolysis. [105] [106] For an extrasolar system, an icy body from beyond the frost line could migrate into the habitable zone of its star, creating an ocean planet with seas hundreds of kilometers deep [107] such as GJ 1214 b [108] [109] or Kepler-22b may be. [110]

Maintenance of liquid surface water also requires a sufficiently thick atmosphere. Possible origins of terrestrial atmospheres are currently theorised to outgassing, impact degassing and ingassing. [111] Atmospheres are thought to be maintained through similar processes along with biogeochemical cycles and the mitigation of atmospheric escape. [112] In a 2013 study led by Italian astronomer Giovanni Vladilo, it was shown that the size of the circumstellar habitable zone increased with greater atmospheric pressure. [74] Below an atmospheric pressure of about 15 millibars, it was found that habitability could not be maintained [74] because even a small shift in pressure or temperature could render water unable to form as a liquid. [113]

Although traditional definitions of the habitable zone assume that carbon dioxide and water vapor are the most important greenhouse gases (as they are on the Earth), [29] a study [49] led by Ramses Ramirez and co-author Lisa Kaltenegger has shown that the size of the habitable zone is greatly increased if prodigious volcanic outgassing of hydrogen is also included along with the carbon dioxide and water vapor. The outer edge in the Solar System would extend out as far as 2.4 AU in that case. Similar increases in the size of the habitable zone were computed for other stellar systems. An earlier study by Ray Pierrehumbert and Eric Gaidos [48] had eliminated the CO2-H2O concept entirely, arguing that young planets could accrete many tens to hundreds of bars of hydrogen from the protoplanetary disc, providing enough of a greenhouse effect to extend the solar system outer edge to 10 AU. In this case, though, the hydrogen is not continuously replenished by volcanism and is lost within millions to tens-of-millions of years.

In the case of planets orbiting in the CHZs of red dwarf stars, the extremely close distances to the stars cause tidal locking, an important factor in habitability. For a tidally locked planet, the sidereal day is as long as the orbital period, causing one side to permanently face the host star and the other side to face away. In the past, such tidal locking was thought to cause extreme heat on the star-facing side and bitter cold on the opposite side, making many red dwarf planets uninhabitable however, three-dimensional climate models in 2013 showed that the side of a red dwarf planet facing the host star could have extensive cloud cover, increasing its bond albedo and reducing significantly temperature differences between the two sides. [84]

Planetary-mass natural satellites have the potential to be habitable as well. However, these bodies need to fulfill additional parameters, in particular being located within the circumplanetary habitable zones of their host planets. [37] More specifically, moons need to be far enough from their host giant planets that they are not transformed by tidal heating into volcanic worlds like Io, [37] but must remain within the Hill radius of the planet so that they are not pulled out of the orbit of their host planet. [114] Red dwarfs that have masses less than 20% of that of the Sun cannot have habitable moons around giant planets, as the small size of the circumstellar habitable zone would put a habitable moon so close to the star that it would be stripped from its host planet. In such a system, a moon close enough to its host planet to maintain its orbit would have tidal heating so intense as to eliminate any prospects of habitability. [37]

A planetary object that orbits a star with high orbital eccentricity may spend only some of its year in the CHZ and experience a large variation in temperature and atmospheric pressure. This would result in dramatic seasonal phase shifts where liquid water may exist only intermittently. It is possible that subsurface habitats could be insulated from such changes and that extremophiles on or near the surface might survive through adaptions such as hibernation (cryptobiosis) and/or hyperthermostability. Tardigrades, for example, can survive in a dehydrated state temperatures between 0.150 K (−273 °C) [115] and 424 K (151 °C). [116] Life on a planetary object orbiting outside CHZ might hibernate on the cold side as the planet approaches the apastron where the planet is coolest and become active on approach to the periastron when the planet is sufficiently warm. [117]

Among exoplanets, a review in 2015 came to the conclusion that Kepler-62f, Kepler-186f and Kepler-442b were likely the best candidates for being potentially habitable. [118] These are at a distance of 1200, 490 and 1,120 light-years away, respectively. Of these, Kepler-186f is similar in size to Earth with a 1.2-Earth-radius measure, and it is located towards the outer edge of the habitable zone around its red dwarf star. Among nearest terrestrial exoplanet candidates, Tau Ceti e is 11.9 light-years away. It is in the inner edge of its solar system's habitable zone, giving it an estimated average surface temperature of 68 °C (154 °F). [119]

Studies that have attempted to estimate the number of terrestrial planets within the circumstellar habitable zone tend to reflect the availability of scientific data. A 2013 study by Ravi Kumar Kopparapu put ηe, the fraction of stars with planets in the CHZ, at 0.48, [4] meaning that there may be roughly 95–180 billion habitable planets in the Milky Way. [120] However, this is merely a statistical prediction only a small fraction of these possible planets have yet been discovered. [121]

Previous studies have been more conservative. In 2011, Seth Borenstein concluded that there are roughly 500 million habitable planets in the Milky Way. [122] NASA's Jet Propulsion Laboratory 2011 study, based on observations from the Kepler mission, raised the number somewhat, estimating that about "1.4 to 2.7 percent" of all stars of spectral class F, G, and K are expected to have planets in their CHZs. [123] [124]

### Early findings Edit

The first discoveries of extrasolar planets in the CHZ occurred just a few years after the first extrasolar planets were discovered. However these early detections were all gas giant sized, and many in eccentric orbits. Despite this, studies indicate the possibility of large, Earth-like moons around these planets supporting liquid water. [125] One of the first discoveries was 70 Virginis b, a gas giant initially nicknamed "Goldilocks" due to it being neither "too hot" nor "too cold". Later study revealed temperatures analogous to Venus, ruling out any potential for liquid water. [126] 16 Cygni Bb, also discovered in 1996, has an extremely eccentric orbit that spends only part of its time in the CHZ, such an orbit would causes extreme seasonal effects. In spite of this, simulations have suggested that a sufficiently large companion could support surface water year-round. [127]

Gliese 876 b, discovered in 1998, and Gliese 876 c, discovered in 2001, are both gas giants discovered in the habitable zone around Gliese 876 that may also have large moons. [128] Another gas giant, Upsilon Andromedae d was discovered in 1999 orbiting Upsilon Andromidae's habitable zone.

Announced on April 4, 2001, HD 28185 b is a gas giant found to orbit entirely within its star's circumstellar habitable zone [129] and has a low orbital eccentricity, comparable to that of Mars in the Solar System. [130] Tidal interactions suggest it could harbor habitable Earth-mass satellites in orbit around it for many billions of years, [131] though it is unclear whether such satellites could form in the first place. [132]

HD 69830 d, a gas giant with 17 times the mass of Earth, was found in 2006 orbiting within the circumstellar habitable zone of HD 69830, 41 light years away from Earth. [133] The following year, 55 Cancri f was discovered within the CHZ of its host star 55 Cancri A. [134] [135] Hypothetical satellites with sufficient mass and composition are thought to be able to support liquid water at their surfaces. [136]

Though, in theory, such giant planets could possess moons, the technology did not exist to detect moons around them, and no extrasolar moons had been discovered. Planets within the zone with the potential for solid surfaces were therefore of much higher interest.

### Habitable super-Earths Edit

The 2007 discovery of Gliese 581 c, the first super-Earth in the circumstellar habitable zone, created significant interest in the system by the scientific community, although the planet was later found to have extreme surface conditions that may resemble Venus. [137] Gliese 581 d, another planet in the same system and thought to be a better candidate for habitability, was also announced in 2007. Its existence was later disconfirmed in 2014, but only for short time. As of 2015, the planet has no newer disconfirmations. Gliese 581 g, yet another planet thought to have been discovered in the circumstellar habitable zone of the system, was considered to be more habitable than both Gliese 581 c and d. However, its existence was also disconfirmed in 2014, [138] and astronomers are divided about its existence.

Discovered in August 2011, HD 85512 b was initially speculated to be habitable, [139] but the new circumstellar habitable zone criteria devised by Kopparapu et al. in 2013 place the planet outside the circumstellar habitable zone. [121]

Kepler-22 b, discovered in December 2011 by the Kepler space probe, [140] is the first transiting exoplanet discovered around a Sun-like star. With a radius 2.4 times that of Earth, Kepler-22b has been predicted by some to be an ocean planet. [141] Gliese 667 Cc, discovered in 2011 but announced in 2012, [142] is a super-Earth orbiting in the circumstellar habitable zone of Gliese 667 C. It is one of the most Earth-like planet known.

Gliese 163 c, discovered in September 2012 in orbit around the red dwarf Gliese 163 [143] is located 49 light years from Earth. The planet has 6.9 Earth masses and 1.8–2.4 Earth radii, and with its close orbit receives 40 percent more stellar radiation than Earth, leading to surface temperatures of about 60° C. [144] [145] [146] HD 40307 g, a candidate planet tentatively discovered in November 2012, is in the circumstellar habitable zone of HD 40307. [147] In December 2012, Tau Ceti e and Tau Ceti f were found in the circumstellar habitable zone of Tau Ceti, a Sun-like star 12 light years away. [148] Although more massive than Earth, they are among the least massive planets found to date orbiting in the habitable zone [149] however, Tau Ceti f, like HD 85512 b, did not fit the new circumstellar habitable zone criteria established by the 2013 Kopparapu study. [150] It is now considered as uninhabitable.

### Near Earth-sized planets and Solar analogs Edit

Recent discoveries have uncovered planets that are thought to be similar in size or mass to Earth. "Earth-sized" ranges are typically defined by mass. The lower range used in many definitions of the super-Earth class is 1.9 Earth masses likewise, sub-Earths range up to the size of Venus (

0.815 Earth masses). An upper limit of 1.5 Earth radii is also considered, given that above 1.5 R the average planet density rapidly decreases with increasing radius, indicating these planets have a significant fraction of volatiles by volume overlying a rocky core. [151] A genuinely Earth-like planet – an Earth analog or "Earth twin" – would need to meet many conditions beyond size and mass such properties are not observable using current technology.

A solar analog (or "solar twin") is a star that resembles the Sun. To date, no solar twin with an exact match as that of the Sun has been found. However, some stars are nearly identical to the Sun and are considered solar twins. An exact solar twin would be a G2V star with a 5,778 K temperature, be 4.6 billion years old, with the correct metallicity and a 0.1% solar luminosity variation. [152] Stars with an age of 4.6 billion years are at the most stable state. Proper metallicity and size are also critical to low luminosity variation. [153] [154] [155]

Using data collected by NASA's Kepler Space observatory and the W. M. Keck Observatory, scientists have estimated that 22% of solar-type stars in the Milky Way galaxy have Earth-sized planets in their habitable zone. [156]

On 7 January 2013, astronomers from the Kepler team announced the discovery of Kepler-69c (formerly KOI-172.02), an Earth-size exoplanet candidate (1.7 times the radius of Earth) orbiting Kepler-69, a star similar to our Sun, in the CHZ and expected to offer habitable conditions. [157] [158] [159] [160] The discovery of two planets orbiting in the habitable zone of Kepler-62, by the Kepler team was announced on April 19, 2013. The planets, named Kepler-62e and Kepler-62f, are likely solid planets with sizes 1.6 and 1.4 times the radius of Earth, respectively. [159] [160] [161]

With a radius estimated at 1.1 Earth, Kepler-186f, discovery announced in April 2014, is the closest yet size to Earth of an exoplanet confirmed by the transit method [162] [163] [164] though its mass remains unknown and its parent star is not a Solar analog.

Kapteyn b, discovered in June 2014 is a possible rocky world of about 4.8 Earth masses and about 1.5 earth radii was found orbiting the habitable zone of the red subdwarf Kapteyn's Star, 12.8 light-years away. [165]

On 6 January 2015, NASA announced the 1000th confirmed exoplanet discovered by the Kepler Space Telescope. Three of the newly confirmed exoplanets were found to orbit within habitable zones of their related stars: two of the three, Kepler-438b and Kepler-442b, are near-Earth-size and likely rocky the third, Kepler-440b, is a super-Earth. [166] However, Kepler-438b is found to be a subject of powerful flares, so it is now considered uninhabitable. 16 January, K2-3d a planet of 1.5 Earth radii was found orbiting within the habitable zone of K2-3, receiving 1.4 times the intensity of visible light as Earth. [167]

Kepler-452b, announced on 23 July 2015 is 50% bigger than Earth, likely rocky and takes approximately 385 Earth days to orbit the habitable zone of its G-class (solar analog) star Kepler-452. [168] [169]

The discovery of a system of three tidally-locked planets orbiting the habitable zone of an ultracool dwarf star, TRAPPIST-1, was announced in May 2016. [170] The discovery is considered significant because it dramatically increases the possibility of smaller, cooler, more numerous and closer stars possessing habitable planets.

Two potentially habitable planets, discovered by the K2 mission in July 2016 orbiting around the M dwarf K2-72 around 227 light year from the Sun: K2-72c and K2-72e are both of similar size to Earth and receive similar amounts of stellar radiation. [171]

Announced on the 20 April 2017, LHS 1140b is a super-dense super-Earth 39 light years away, 6.6 times Earth's mass and 1.4 times radius, its star 15% the mass of the Sun but with much less observable stellar flare activity than most M dwarfs. [172] The planet is one of few observable by both transit and radial velocity that's mass is confirmed with an atmosphere may be studied.

Discovered by radial velocity in June 2017, with approximately three times the mass of Earth, Luyten b orbits within the habitable zone of Luyten's Star just 12.2 light-years away. [173]

At 11 light-years away, a second closest planet, Ross 128 b, was announced in November 2017 following a decade's radial velocity study of relatively "quiet" red dwarf star Ross 128. At 1.35 Earth's mass is it roughly Earth-sized and likely rocky in composition. [174]

Discovered in March 2018, K2-155d is about 1.64 time the radius of Earth, is likely rocky and orbits in the habitable zone of its red dwarf star 203 light years away. [175] [176] [177]

One of the earliest discoveries by the Transiting Exoplanet Survey Satellite (TESS) announced July 31, 2019 is a Super Earth planet GJ 357 d orbiting the outer edge of a red dwarf 31 light years away. [178]

K2-18b is an exoplanet 124 light-years away, orbiting in the habitable zone of the K2-18, a red dwarf. This planet is significant for water vapour found in its atmosphere this was announced on September 17, 2019.

In September 2020, astronomers identified 24 superhabitable planet (planets better than Earth) contenders, from among more than 4000 confirmed exoplanets at present, based on astrophysical parameters, as well as the natural history of known life forms on the Earth. [179]

Notable exoplanets – Kepler Space Telescope
Confirmed small exoplanets in habitable zones.
(Kepler-62e, Kepler-62f, Kepler-186f, Kepler-296e, Kepler-296f, Kepler-438b, Kepler-440b, Kepler-442b)
(Kepler Space Telescope January 6, 2015). [166]

Liquid-water environments have been found to exist in the absence of atmospheric pressure, and at temperatures outside the CHZ temperature range. For example, Saturn's moons Titan and Enceladus and Jupiter's moons Europa and Ganymede, all of which are outside the habitable zone, may hold large volumes of liquid water in subsurface oceans. [180]

Outside the CHZ, tidal heating and radioactive decay are two possible heat sources that could contribute to the existence of liquid water. [16] [17] Abbot and Switzer (2011) put forward the possibility that subsurface water could exist on rogue planets as a result of radioactive decay-based heating and insulation by a thick surface layer of ice. [19]

With some theorising that life on Earth may have actually originated in stable, subsurface habitats, [181] [182] it has been suggested that it may be common for wet subsurface extraterrestrial habitats such as these to 'teem with life'. [183] Indeed, on Earth itself living organisms may be found more than 6 kilometres below the surface. [184]

Another possibility is that outside the CHZ organisms may use alternative biochemistries that do not require water at all. Astrobiologist Christopher McKay, has suggested that methane ( CH
4 ) may be a solvent conducive to the development of "cryolife", with the Sun's "methane habitable zone" being centered on 1,610,000,000 km (1.0 × 10 9 mi 11 AU) from the star. [23] This distance is coincident with the location of Titan, whose lakes and rain of methane make it an ideal location to find McKay's proposed cryolife. [23] In addition, testing of a number of organisms has found some are capable of surviving in extra-CHZ conditions. [185]

The Rare Earth hypothesis argues that complex and intelligent life is uncommon and that the CHZ is one of many critical factors. According to Ward & Brownlee (2004) and others, not only is a CHZ orbit and surface water a primary requirement to sustain life but a requirement to support the secondary conditions required for multicellular life to emerge and evolve. The secondary habitability factors are both geological (the role of surface water in sustaining necessary plate tectonics) [35] and biochemical (the role of radiant energy in supporting photosynthesis for necessary atmospheric oxygenation). [186] But others, such as Ian Stewart and Jack Cohen in their 2002 book Evolving the Alien argue that complex intelligent life may arise outside the CHZ. [187] Intelligent life outside the CHZ may have evolved in subsurface environments, from alternative biochemistries [187] or even from nuclear reactions. [188]

On Earth, several complex multicellular life forms (or eukaryotes) have been identified with the potential to survive conditions that might exist outside the conservative habitable zone. Geothermal energy sustains ancient circumvental ecosystems, supporting large complex life forms such as Riftia pachyptila. [189] Similar environments may be found in oceans pressurised beneath solid crusts, such as those of Europa and Enceladus, outside of the habitable zone. [190] Numerous microorganisms have been tested in simulated conditions and in low Earth orbit, including eukaryotes. An animal example is the Milnesium tardigradum, which can withstand extreme temperatures well above the boiling point of water and the cold vacuum of outer space. [191] In addition, the lichens Rhizocarpon geographicum and Xanthoria elegans have been found to survive in an environment where the atmospheric pressure is far too low for surface liquid water and where the radiant energy is also much lower than that which most plants require to photosynthesize. [192] [193] [194] The fungi Cryomyces antarcticus and Cryomyces minteri are also able to survive and reproduce in Mars-like conditions. [194]

Species, including humans, known to possess animal cognition require large amounts of energy, [195] and have adapted to specific conditions, including an abundance of atmospheric oxygen and the availability of large quantities of chemical energy synthesized from radiant energy. If humans are to colonize other planets, true Earth analogs in the CHZ are most likely to provide the closest natural habitat this concept was the basis of Stephen H. Dole's 1964 study. With suitable temperature, gravity, atmospheric pressure and the presence of water, the necessity of spacesuits or space habitat analogues on the surface may be eliminated, and complex Earth life can thrive. [2]

Planets in the CHZ remain of paramount interest to researchers looking for intelligent life elsewhere in the universe. [196] The Drake equation, sometimes used to estimate the number of intelligent civilizations in our galaxy, contains the factor or parameter ne , which is the average number of planetary-mass objects orbiting within the CHZ of each star. A low value lends support to the Rare Earth hypothesis, which posits that intelligent life is a rarity in the Universe, whereas a high value provides evidence for the Copernican mediocrity principle, the view that habitability—and therefore life—is common throughout the Universe. [35] A 1971 NASA report by Drake and Bernard Oliver proposed the "water hole", based on the spectral absorption lines of the hydrogen and hydroxyl components of water, as a good, obvious band for communication with extraterrestrial intelligence [197] [198] that has since been widely adopted by astronomers involved in the search for extraterrestrial intelligence. According to Jill Tarter, Margaret Turnbull and many others, CHZ candidates are the priority targets to narrow waterhole searches [199] [200] and the Allen Telescope Array now extends Project Phoenix to such candidates. [201]

Because the CHZ is considered the most likely habitat for intelligent life, METI efforts have also been focused on systems likely to have planets there. The 2001 Teen Age Message and the 2003 Cosmic Call 2, for example, were sent to the 47 Ursae Majoris system, known to contain three Jupiter-mass planets and possibly with a terrestrial planet in the CHZ. [202] [203] [204] [205] The Teen Age Message was also directed to the 55 Cancri system, which has a gas giant in its CHZ. [134] A Message from Earth in 2008, [206] and Hello From Earth in 2009, were directed to the Gliese 581 system, containing three planets in the CHZ—Gliese 581 c, d, and the unconfirmed g.

## Subaru Telescope Reveals Active Supermassive Black Holes in Merging Galaxies

Astronomers used the Subaru Telescope to study active supermassive black holes in merging galaxies, revealing that local physical conditions near SMBHs rather than general properties of galaxies primarily determine the activation of SMBHs.

A team of astronomers has conducted infrared observations of luminous, gas-rich, merging galaxies with the Subaru Telescope to study active, mass-accreting supermassive black holes (SMBHs). They found that at least one SMBH almost always becomes active and luminous by accreting a large amount of material. However, only a small fraction of the observed merging galaxies show multiple, active SMBHs. These results suggest that local physical conditions near SMBHs rather than general properties of galaxies primarily determine the activation of SMBHs.

In this Universe, dark matter has a much higher mass than luminous matter, and it dominates the formation of galaxies and their large-scale structures. The widely accepted, cold-dark-matter based galaxy formation scenario posits that collisions and mergers of small gas-rich galaxies result in the formation of massive galaxies seen in the current Universe. Recent observations show that SMBHs with more than one-million solar masses ubiquitously exist in the center of galaxies. The merger of gas-rich galaxies with SMBHs in their centers not only causes active star formation but also stimulates mass accretion onto the existing SMBHs. When material accretes onto a supermassive black hole (SMBH), the accretion disk surrounding the black hole becomes very hot from the release of gravitational energy, and it becomes very luminous. This process is referred to as active galactic nucleus (AGN) activity it is different from the energy generation activity by nuclear fusion reactions within stars. Understanding the difference between these kinds of activities is crucial for clarifying the physical processes of galaxy formation. However, observation of these processes is challenging, because dust and gas shroud both star-formation and AGN activities in merging galaxies. Infrared observations are indispensable for this type of research, because they substantially reduce the effects of dust extinction.

To better understand these activities, a team of astronomers at the National Astronomical Observatory of Japan (NAOJ), led by Dr. Masatoshi Imanishi, used Subaru Telescope’s Infrared Camera and Spectrograph (IRCS) and its adaptive optics system to observe infrared luminous merging galaxies at the infrared K-band (a wavelength of 2.2 micrometers) and L’-band (a wavelength of 3.8 micrometers). They used imaging data at these wavelengths to establish a method to differentiate the activities of deeply buried, active SMBHs from those of star formation. The radiative energy-generation efficiency from active, mass-accreting SMBHs is much higher than that of the nuclear fusion reactions inside stars. An active SMBH generates a large amount of hot dust (several 100 Kelvins), which produces strong infrared L’-band radiation the relative strengths of the infrared K- and L’-band emission distinguish the active SMBH from star-forming activity. Since dust extinction effects are small at these infrared wavelengths, the method can detect even deeply buried, active SMBHs, which are elusive in optical wavelengths. Subaru Telescope’s adaptive optics system enabled the team to obtain high spatial resolution images that allowed them to effectively investigate emission that originates in active SMBHs in the nuclear regions of galaxies by minimizing emission contamination from galaxy-wide, star-forming activity.

The team observed 29 infrared luminous gas-rich merging galaxies. Based on the relative strength of the infrared K- and L’-band emission at galaxy nuclei, they confirmed that at least one active SMBH occurs in every galaxy but one (Figure 2). This indicates that in gas-rich, merging galaxies, a large amount of material can accrete onto SMBHs, and many such SMBHs can show AGN activity.

Figure 2: Examples of infrared K-band images of luminous, gas-rich, merging galaxies. The image size is 10 arc seconds. North is up, and east is to the left. The individual images clearly show aspects of the merging process, such as interacting double galaxy nuclei and extended/bridging faint emission structure. (Credit: NAOJ)

However, only four merging galaxies display multiple, active SMBHs (Figure 3). If both of the original merged galaxies had SMBHs, then we would expect that multiple SMBHs would occur in many merging galaxies. To observe these SMBHs as luminous AGN activity, the SMBHs must actively accrete material. The team’s results mean that not all SMBHs in gas-rich merging galaxies are actively mass accreting, and that multiple SMBHs may have considerably different mass accretion rates onto SMBHs. Quantitative measurement of the degree of mass accretion rates of SMBHs is usually based on the brightness of AGNs per unit SMBH mass (Figure 4). Comparison of SMBH-mass-normalized AGN luminosity (=AGN luminosity divided by SMBH mass) among multiple nuclei confirms the scenario of different mass accretion rates onto multiple SMBHs in infrared-luminous, gas-rich merging galaxies.

Figure 3: Infrared K-band and L’-band images of four luminous, gas-rich, merging galaxies that display multiple, active SMBHs. The image size is 10 arc seconds. North is up, and east is to the left. They show emission from multiple galaxy nuclei. The infrared K-band to L’-band emission strength ratios characterize emission of AGN-heated hot dust, not a star-formation-related one. (Credit: NAOJ)

Figure 4: The vertical axis is the comparison of SMBH-mass-normalized AGN luminosity (= AGN luminosity divided by SMBH mass) between multiple nuclei. The horizontal axis is the apparent separation of galaxy nuclei. 1 kilo-parsec corresponds to 30000 trillion kilometers (19000 trillion miles). The supermassive black-hole (SMBH) masses are derived from stellar emission luminosity at individual galaxy nuclei, because SMBH mass and galaxy stellar emission luminosity are found to correlate in nearby galaxies. If both SMBHs have the same mass accretion rate, when normalized to the SMBH mass, then such objects are distributed around the horizontal solid line, at the value of unity in the vertical axis. Objects above the horizontal solid line are SMBHs with larger mass and show more active mass accretion, while those below have a smaller mass and show less active mass accretion.(Credit: NAOJ)

The findings demonstrate that local conditions around SMBHs rather than general properties of galaxies dominate the mass accretion process onto SMBHs. Since the size scale of mass accretion onto SMBHs is very small compared to the galaxy scale, such phenomena are difficult to predict based on computer simulations of galaxy mergers. Actual observations are crucially important for best understanding the mass accretion process onto SMBHs that occurs during galaxy mergers.

Publication: Masatoshi Imanishi and Yuriko Saito, “Subaru Adaptive-optics High-spatial-resolution Infrared K- and L’-band Imaging Search for Deeply Buried Dual AGNs in Merging Galaxies,” 2014, ApJ, 780, 106 doi:10.1088/0004-637X/780/1/106

## UH REU student helps reveal how galaxies and black holes grow together

Over the past two decades, astronomers have concluded that most, if not all, galaxies host massive black holes at their centers - and the masses of a black hole and its host galaxy are correlated. But how are the two connected? Now, a University of Hawaiʻi at Mānoa Institute for Astronomy (IfA) student participating in the National Science Foundation's (NSF) Research Experiences for Undergraduates (REU) program, may have revealed part of the answer.

Undergraduate Rebecca Minsley, participated in IfA's 2019 REU program, working for ten weeks with her mentor Maunakea Spectroscopic Explorer Deputy Project Scientist Andreea Petric. Sifting meticulously though hundreds of images of galaxies, Minsley began to define a clearer picture of galaxy evolution. "Galaxy growth may be shaped by interactions with other galaxies which contributes to supermassive black holes (SMBH) that grow within the galaxy's center," Minsley explained.

Gas and dust between stars, called the interstellar medium (ISM), is the fuel for both SMBH growth and the formation of new stars. But recent work shows that the ISM may have different properties - especially being warmer - in galaxies that host a growing supermassive black hole in their nuclei, compared to those galaxies that do not. Warmer gas is less likely to collapse into new stars, so this finding may suggest that a growing central SMBH diminishes a galaxy's ability to make new stars.

What might be responsible for heating the ISM? Starlight, especially from hot stars, can do this. But interactions between galaxies - when they collide or even just pass close to each other - can produce large-scale shock waves that compress less dense gas, making it more likely to form stars. Minsley studied the shapes of 630 galaxies using images from the Pan-STARRS survey. She classified the galaxies into mergers, early mergers, and non-mergers. And then compared the shapes to the light output of the same galaxies at longer mid-infrared wavelengths, where she could study the properties of the ISM.

"When galaxies get close enough they go through a sort of galactic dance until they eventually coalesce into a singular entity. These interactions have well documented signatures that allowed me to categorize our set of galaxies." Minsley said. "This project gave me a greater appreciation for the complexity and entanglement of all the processes taking place inside galaxies and the research being done to deconstruct galactic systems is fascinating."

Minsley and collaborators found that within galaxies with active black holes, the ISM is warmer, the ratios of warm molecular gas to other coolants are larger, and other features from dust particles have a wider range of values than in galaxies where the black holes are dormant.

"In the nearby universe we find that the warm ISM of galaxies which host growing supermassive black holes at their centers differs from those that do not," explains Petric. "We speculate that the same processes that funnel fuel to the SMBH also allow us to detect the energy transfer back into the galaxy's ISM." Petric adds that future, more detailed observations, will allow researchers confirm these energy transfer processes.

IfA has been part of the prestigious REU program for almost 20 years, training over 130 students, some of whom are now leaders in different fields of astronomy. Because of this unique opportunity to work in Hawaii with world class facilities and scientists, the IfA receives over 500 applications each term. The focus of their REU program is on identifying students who have potential to succeed in research, but may not have the opportunity and resources.

Nader Haghighipour, the Principal Investigator of IfA's REU program, noted "With our mentors among the world leaders in their respective fields, our REU students are engaged in cutting edge research. Rebecca's work is a prime example of this. We are very proud of our REU students, as almost all of them continued their studies in graduate school, and many of them have gained national recognition."

During the 2020 fall semester, Petric and UH Mānoa undergraduate Diana Castaneda will continue to investigate the ISM of galaxies hosting some of the most luminous growing SMBH in the nearby universe, using a spectrometer aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) aircraft. The SOFIA observations will allow Castaneda and Petric to gain more insight into the processes by which energy is being transferred between the growing SMBH and the ISM.

This work is published in the May 10th issue of the Astrophysical Journal and is available in preprint form on ArXiv.

Pan-STARRS images of NGC 4088, NGC 0520, NGC 5218, NGC 4922 NED02, illustrating the different features used to classify galaxy mergers, including galaxy asymmetry, tidal tails, galactic shells, multiple nuclei and early/possible mergers for galaxies of similar brightness within 50 kpc of each-other.

Founded in 1967, the Institute for Astronomy at the University of Hawaiʻi at Mānoa conducts research into galaxies, cosmology, stars, planets, and the sun. Its faculty and staff are also involved in astronomy education, deep space missions, and in the development and management of the observatories on Haleakalā and Maunakea. The Institute operates facilities on the islands of Oahu, Maui, and Hawaiʻi.

## Does the dust around SMBH's protect habitable planets from jets? - Astronomy

SYDNEY .- A discovery that links stellar flares with radio-burst signatures will make it easier for astronomers to detect space weather around nearby stars outside the Solar System. Unfortunately, the first weather reports from our nearest neighbour, Proxima Centauri, are not promising for finding life as we know it.

“Astronomers have recently found there are two ‘Earth-like’ rocky planets around Proxima Centauri, one within the ‘habitable zone’ where any water could be in liquid form,” said Andrew Zic from the University of Sydney.

Proxima Centauri is just 4.2 light years from Earth.

“But given Proxima Centauri is a cool, small red-dwarf star, it means this habitable zone is very close to the star much closer in than Mercury is to our Sun,” he said.

“What our research shows is that this makes the planets very vulnerable to dangerous ionising radiation that could effectively sterilise the planets.”

Led by Mr Zic, astronomers have for the first time shown a definitive link between optical flares and radio bursts on a star that is not the Sun. The finding, published today in The Astrophysical Journal, is an important step to using radio signals from distant stars to effectively produce space weather reports.

“Our own Sun regularly emits hot clouds of ionised particles during what we call ‘coronal mass ejections’. But given the Sun is much hotter than Proxima Centauri and other red-dwarf stars, our ‘habitable zone’ is far from the Sun’s surface, meaning the Earth is a relatively long way from these events,” Mr Zic said.

“Further, the Earth has a very powerful planetary magnetic field that shields us from these intense blasts of solar plasma.”

The research was done in collaboration with CSIRO, the University of Western Australia, University of Wisconsin-Milwaukee, University of Colorado and Curtin University. There were contributions from the ARC Centre for Gravitational Waves and University of California Berkeley.

The study formed part of Mr Zic’s doctoral studies at the Sydney Institute for Astronomy under the supervision of Professor Tara Murphy, deputy head of the School of Physics at the University of Sydney. Mr Zic has now taken a joint position at Macquarie University and CSIRO.

He said: “M-dwarf radio bursts might happen for different reasons than on the Sun, where they are usually associated with coronal mass ejections. But it’s highly likely that there are similar events associated with the stellar flares and radio bursts we have seen in this study.”

Coronal mass ejections are hugely energetic expulsions of ionised plasma and radiation leaving the stellar atmosphere.

“This is probably bad news on the space weather front. It seems likely that the galaxy’s most common stars – red dwarfs – won’t be great places to find life as we know it,” Mr Zic said.

In the past decade, there has been a renaissance in the discovery of planets orbiting stars outside our Solar System. There are now more than 4000 known exoplanets.

This has boosted hopes of finding ‘Earth-like’ conditions on exoplanets. Recent research says that about half the Sun-like stars in the Milky Way could be home to such planets. However, Sun-like stars only make up 7 percent of the galaxy’s stellar objects. By contrast, M-type red dwarfs like Proxima Centauri make up about 70 percent of stars in the Milky Way.

The findings strongly suggest planets around these stars are likely to be showered with stellar flares and plasma ejections.

Methodology
The Proxima Centauri observations were taken with the CSIRO’s Australian Square Kilometre Array Pathfinder (ASKAP) telescope in Western Australia, the Zadko Telescope at the University of Western Australia and a suite of other instruments.

University of Western Australia scientist Dr Bruce Gendre, from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), said the research helps understand the dramatic effects of space weather on solar systems beyond our own.

“Understanding space weather is critical for understanding how our own planet biosphere evolved – but also for what the future is,” Dr Gendre said.

Professor Murphy said: “This is an exciting result from ASKAP. The incredible data quality allowed us to view the stellar flare from Proxima Centauri over its full evolution in amazing detail.

“Most importantly, we can see polarised light, which is a signature of these events. It’s a bit like looking at the star with sunglasses on. Once ASKAP is operating in full survey mode we should be able to observe many more events on nearby stars.”

This will give us much greater insights to the space weather around nearby stars.

Other facilities, including NASA’s planet-hunting Transiting Exoplanet Survey Satellite and the Zadko Telescope observed simultaneously with ASKAP providing the crucial link between the radio bursts and powerful optical flares observed.

Mr Zic said: “The probability that the observed solar flare and received radio signal from our neighbour were not connected is much less than one chance in 128,000.”

The research shows that planets around Proxima Centauri may suffer strong atmospheric erosion, leaving them exposed to very intense X-rays and ultraviolet radiation.

But could there be magnetic fields protecting these planets?

Mr Zic said: “This remains an open question. How many exoplanets have magnetic fields like ours?”

So far there have been no observations of magnetic fields around exoplanets and finding these could prove tricky. Mr Zic said one potential way to identify distant magnetic fields would be to look for aurorae, like those around Earth and also witnessed on Jupiter.

“But even if there were magnetic fields, given the stellar proximity of habitable zone planets around M-dwarf stars, this might not be enough to protect them,” Mr Zic said.

Declaration
Andrew Zic was funded by an Australian Government Research Training Program Scholarship. Tara Murphy acknowledges the support of the Australian Research Council. Parts of this research were conducted by the Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav). This research was supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D).

## Universe Today

This episode was recorded live in St. Louis, MO at the Astronomy Cast Solar Eclipse Escape 2017, so there’s only audio, no video. Listen here at Astronomy Cast as we discuss how humans might be able to colonize the Milky Way!

We usually record Astronomy Cast every Friday at 1:30 pm PDT / 4:30 pm EDT/ 20:30 PM UTC (8:30 GMT). You can watch us live on AstronomyCast.com, or the AstronomyCast YouTube page.
Visit the Astronomy Cast Page to subscribe to the audio podcast!

### NASA Completes Critical Space Communications Network with Spectacular Launch of Final TDRS Science Relay Satellite

NASA’s Tracking and Data Relay Satellite-M (TDRS-M), which is the third and final in a series of next generation science communications satellites, was successfully launched Aug. 18, 2017 at 8:29 a.m. EDT by a United Launch Alliance (ULA) Atlas V rocket from Space Launch Complex-41 on Cape Canaveral Air Force Station in Florida. TDRS-M has been placed into orbit following separation from the upper stage. Credit: Ken Kremer/kenkremer.com

KENNEDY SPACE CENTER, FL – Today marked the end of an era for NASA as the last of the agency’s next generation Tracking and Data Relay Satellites (TRDS) that transmit the critical science data and communications for the Hubble Space Telescope and human spaceflight missions to the International Space Station, successfully rocketed to orbit this morning, Fri. Aug 18 from the Florida Space Coast.

The spectacular liftoff of the strangely fish-like TDRS-M science relay comsat atop a United Launch Alliance Atlas V rocket occurred at 8:29 a.m. EDT a.m. (2:29 GMT) Aug. 18 from Space Launch Complex 41 at Cape Canaveral Air Force Station.

The weather cooperated with relatively thin but artistic clouds and low winds and offered spectators a spectacular launch show that will not forget.

NASA’s $408 million next generation Tracking and Data Relay Satellites (TRDS) looks like a giant alien fish or cocooned creature. But actually plays an unparalleled role in relaying critical science measurements, research data and tracking observations gathered by the International Space Station (ISS), Hubble and a plethora of Earth science missions. “TDRS is a critical national asset have because of its importance to the space station and all of our science missions, primarily the Hubble Space Telescope and Earth science missions that use TDRS,” said Tim Dunn, NASA’s TDRS-M launch director. NASA’s Tracking and Data Relay Satellite-M (TDRS-M), which is the third and final in a series of next generation science communications satellites, was successfully launched Aug. 18, 2017 at 8:29 a.m. EDT by a United Launch Alliance (ULA) Atlas V rocket from Space Launch Complex-41 on Cape Canaveral Air Force Station in Florida. TDRS-M has been placed into orbit following separation from the upper stage. Credit: Ken Kremer/kenkremer.com TDRS-M will provide high-bandwidth communications to spacecraft in low-Earth orbit. The TDRS network enables continuous communication with the International Space Station, the Hubble Space Telescope, the Earth Observing System and other programs supporting human space flight, said satellite builder Boeing, the prime contractor for the mission. TDRS-M is the last of three satellites to be launched in the third generation of TDRS satellites. It is also the final satellite built based on Boeing’s 601 spacecraft bus series. NASA plans to switch to much higher capacity laser communications for the next generation of TDRS-like satellites and therefore opted to not build a fourth third generation satellite after TDRS-M. Inside the Astrotech payload processing facility in Titusville, FL,NASA’s massive, insect like Tracking and Data Relay Satellite, or TDRS-M, spacecraft is undergoing preflight processing during media visit on 13 July 2017. TDRS-M will transmit critical science data gathered by the ISS, Hubble and numerous NASA Earth science missions. It is being prepared for encapsulation inside its payload fairing prior to being transported to Launch Complex 41 at Cape Canaveral Air Force Station for launch on a United Launch Alliance (ULA) Atlas V rocket on 3 August 2017. Credit: Ken Kremer/kenkremer.com “The TDRS fleet is a critical connection delivering science and human spaceflight data to those who can use it here on Earth,” said Dave Littmann, the TDRS project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “TDRS-M will expand the capabilities and extend the lifespan of the Space Network, allowing us to continue receiving and transmitting mission data well into the next decade.” Launch of ULA Atlas V on TDRS-M mission for NASA from Cape Canaveral Air Force Station in Florida on Aug. 18, 2017 at 8:29 a.m. EDT. Credit: Julian Leek TDRS-M joins a constellation of 9 TDRS satellites already in orbit and ups the fleet to ten orbiting satellites. Evolution of NASA’s Tracking and Data Relay Satellite (TDRS) System. Credit: NASA The Atlas V rocket and Centaur upper stage delivered TDRS-M to its desired preliminary orbit. “Trajectory analysis in. Injection accuracy was within 1% of prediction #TDRSM,” tweeted ULA CEO Torey Bruno. Several hours after the launch ground controllers reported the satellite was in good health. On tap now is a four month period or orbit checkout by prime contractor Boeing as well as a series of five significant orbit raising maneuvers from its initial orbit to Geostationary orbit over the Pacific Ocean. “This TDRS-M milestone is another step forward in Boeing’s commitment to developing technologies to support future NASA near-Earth, moon, Mars and deep space missions – and to do so affordably, drawing on our 40-plus years of strong Boeing-NASA partnership,” said Enrico Attanasio, executive director, Department of Defense and Civil Programs, Boeing Satellite Systems. Ground controllers will then move it to its final orbit over the Atlantic Ocean. NASA plans to conduct additional tests before putting TDRS-M into service early next year over the Atlantic. Blastoff of NASA’s Tracking and Data Relay Satellite-M (TDRS-M) on Aug. 18, 2017 at 8:29 a.m. EDT by a United Launch Alliance (ULA) Atlas V rocket from Space Launch Complex-41 on Cape Canaveral Air Force Station in Florida – as seen from the VAB roof. Credit: Ken Kremer/kenkremer.com The importance of the TDRS constellation of satellites can’t be overstated. Virtually all the communications relay capability involving human spaceflight, such as the ISS, resupply vehicles like the SpaceX cargo Dragon and Orbital ATK Cygnus and the soon to launch human space taxis like crew Dragon, Boeing Starliner and NASA’s Orion deep space crew capsule route their science results voice, data, command, telemetry and communications via the TDRS network of satellites. The TDRS constellation enables both space to space and space to ground communications for virtually the entire orbital period. The two stage Atlas V rocket stands 191 feet tall. TDRS-M, spacecraft, which stands for Tracking and Data Relay Satellite – M is NASA’s new and advanced science data relay communications satellite that will transmit research measurements and analysis gathered by the astronaut crews and instruments flying abroad the International Space Station (ISS), Hubble Space Telescope and over 35 NASA Earth science missions including MMS, GPM, Aura, Aqua, Landsat, Jason 2 and 3 and more. The TDRS constellation orbits 22,300 miles above Earth and provide near-constant communication links between the ground and the orbiting satellites. TRDS-M will have S-, Ku- and Ka-band capabilities. Ka has the capability to transmit as much as six-gigabytes of data per minute. That’s the equivalent of downloading almost 14,000 songs per minute says NASA. The TDRS program is managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland. TDRS-M is the third satellite in the third series of NASA’s American’s most powerful and most advanced Tracking and Data Relay Satellites. It is designed to last for a 15 year orbital lifetime. The first TDRS satellite was deployed from the Space Shuttle Challenger in 1983 as TDRS-A. TDRS-M was built by prime contractor Boeing in El Segundo, California and is the third of a three satellite series – comprising TDRS -K, L, and M. They are based on the Boeing 601 series satellite bus and will be keep the TDRS satellite system operational through the 2020s. TDSR-K and TDRS-L were launched in 2013 and 2014. Configuration diagram of NASA’s Tracking and Data Relay Satellites. Credit: NASA The Tracking and Data Relay Satellite project is managed at NASA’s Goddard Space Flight Center. TDRS-M was built as a follow on and replacement satellite necessary to maintain and expand NASA’s Space Network, according to a NASA description. The gigantic satellite is about as long as two school buses and measures 21 meters in length by 13.1 meters wide. It has a dry mass of 1800 kg (4000 lbs) and a fueled mass of 3,454 kilogram (7,615 lb) at launch. Watch for Ken’s continuing onsite TDRS-M, CRS-12, ORS 5 and NASA and space mission reports direct from the Kennedy Space Center and Cape Canaveral Air Force Station, Florida. Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news. ### Large Near-Earth Asteroid Will Pass Earth by This September Within Earth’s orbit, there are literally thousands of what are known as Near-Earth Objects (NEOs), more than fourteen thousands of which are asteroids that periodically pass close to Earth. Since the 1980s, these objects have become a growing source of interest to astronomers, due to the threat they sometimes represent. But as ongoing studies and decades of tracking the larger asteroids has shown, they usually just pass Earth by. More importantly, it is only on very rare occasions (i.e. over the course of millions of years) that a larger asteroid will come close to colliding with Earth. For example, this September 1st, the Near-Earth Asteroid (NEA) known as 3122 Florence, will pass by Earth, but poses no danger of hitting us. Good thing too, since this Near-Earth Asteroid is one of the largest yet to be discovered, measuring about 4.4 km (2.7 mi) in diameter! To put that in perspective, the asteroid which is thought to have killed the dinosaurs roughly 65 million years ago (aka. the Cretaceous–Paleogene extinction event) is believed to have measured 10 km (6 mi) in diameter. This impact also destroyed three-quarters of the plant and animal species on Earth, hence why organizations like NASA’s Center for Near-Earth Object Studies (CNEOS) is in he habit of tracking the larger NEAs. Asteroid Florence, a large near-Earth asteroid, will pass safely by Earth on Sept. 1, 2017, at a distance of about 7 million km (4.4 million mi). Credits: NASA/JPL-Caltech Once again, NASA has determined that this particular asteroid will sail harmlessly by, passing Earth at a minimum distance of over 7 million km (4.4 million mi), or about 18 times the distance between the Earth and the Moon. As Paul Chodas – NASA’s manager of CNEOS at the Jet Propulsion Laboratory in Pasadena, California – said in a NASA press statement: “While many known asteroids have passed by closer to Earth than Florence will on September 1, all of those were estimated to be smaller. Florence is the largest asteroid to pass by our planet this close since the NASA program to detect and track near-Earth asteroids began.” Rather than being a threat, the flyby of this asteroid will be an opportunity for scientists to study it up close. NASA is planning on conducting radar studies of Florence using the Goldstone Solar System Radar in California, and the National Science Foundation’s (NSF) Arecibo Observatory in Peurto Rico. These studies are expected to yield more accurate data on its size, and reveal surface details at resolutions of up to 10 m (30 feet). This asteroid was originally discovered on March 2nd, 1981, by American astronomer Schelte Bus at the Siding Spring Observatory in southwestern Australia. It was named in honor of Florence Nightingale (1820-1910) the founder of modern nursing. Measurements obtained by NASA’s Spitzer Space Telescope and the NEOWISE mission are what led to the current estimates on its size – about 4.4 km (2.7 mi) in diameter. Artist’s rendition of how far Florence will pass by Earth. Credits: NASA/JPL-Caltech The upcoming flyby will be the closest this asteroid has passed to Earth since August 31st, 1890, where it passed at a distance of 6.7 million km (4.16 million mi). Between now and then, it also flew by Earth on August 29th, 1930, passing Earth at a distance of about 7.8 million km (4.87 million mi). While it will pass Earth another seven times over the course of the next 500 years, it will not be as close as it will be this September until after 2500. For those interesting into doing a little sky watching, Florence will be brightening substantially by late August and early September. During this time, it will be visible to those using small telescopes for several nights as it moves through the constellations of Piscis Austrinus, Capricornus, Aquarius and Delphinus. Be sure to check out these animations of Florence’s orbit and its close flyby to Earth: ### Another Nearby Red Dwarf Star System, Another Possible Exoplanet Discovered! In the past few years, there has been no shortages of extra-solar planets discoveries which orbit red dwarf stars. In 2016 and 2017 alone, astronomers announced the discovery of a terrestrial (i.e. rocky) planet around Proxima Centauri (Proxima b), a seven-planet system orbiting TRAPPIST-1, and super-Earths orbiting the nearby stars of LHS 1140 (LHS 1140b), and GJ 625 (GJ 625b). In what could be the latest discovery, physicists at the University of Texas Arlington (UTA) recently announced the possible discovery of an Earth-like planet orbiting Gliese 832, a red dwarf star just 16 light years away. In the past, astronomers detected two exoplanets orbiting Gliese 832. But after conducting a series of computations, the UTA team indicated that an additional Earth-like planet could be orbiting the star. The study which details their findings, titled “Dynamics of a Probable Earth-mass Planet in the GJ 832 System“, recently appeared in The Astrophysical Journal. Led by Dr. Suman Satyal – a physics researcher, lecturer and laboratory supervisor at UTA – the team sought to investigate the stability of planetary orbits around Gliese 832 using a numerical and detailed phase-space analysis. Artistic representation of the potentially habitable exoplanet Gliese 832c as compared with Earth. Credit: PHL/UPR Arecibo. As indicated, two other exoplanets had been discovered around Gliese 832 in the past, including a Jupiter-like gas giant (Gliese 832b) in 2008, and the super-Earth (Gliese 832c) in 2014. In many ways, these planets could not be more different. In addition to their disparity in mass, they vary widely in terms of their orbits – with Gliese 832b orbiting at a distance of about 0.16 AU and Gliese 832c orbiting at a distance of 3 to 3.8 AU. Because of this, the UTA team sought to determine if perhaps there was a third planet with a stable orbit between the two. To this end, they conducted numerical simulations for a three and four body system of planets with elliptical orbits around the star. These simulations took into account a large number of initial conditions, which allowed for all possible states (aka. s phase-space simulation) of the planet’s orbits to be represented. They then included the radial velocity measurements of Gliese 832, accounting for them based on the presence of planets with 1 to 15 Earth masses. The Radial Velocity (RV) method, it should be noted, determines the existence of planets around a star based on variations in the star’s velocity. In other words, the fact that a star is moving back and forth indicates that it is being influenced by the presence of a planetary system. Simulating the star’s RV signal using a hypothetical system of planets also allowed the UTA team to constrain the average distances at which these planets would orbit the star (aka. their semi-major axes) and their upper mass-limits. In the end, their results provided strong indications for the existence of a third planet. As Dr. Satyal explained in a UTA press release: “We also used the integrated data from the time evolution of orbital parameters to generate the synthetic radial velocity curves of the known and the Earth-like planets in the system. We obtained several radial velocity curves for varying masses and distances indicating a possible new middle planet.” Diagram showing the possible orbit of a third exoplanet around Gliese 832, a star system located just 16 light years away. Credit: uta.edu/Suman Satyal Based on their computations, this possible planet of the Gliese 832 system would be between 1 and 15 Earth masses and would orbit the star at a distance ranging from 0.25 to 2.0 AU. They also determined that it would likely have a stable orbit for about 1 billion years. As Dr. Satyal indicated, all signs coming from the Gliese 832 system point towards there being a third planet. “The existence of this possible planet is supported by long-term orbital stability of the system, orbital dynamics and the synthetic radial velocity signal analysis,” he said. “At the same time, a significantly large number of radial velocity observations, transit method studies, as well as direct imaging are still needed to confirm the presence of possible new planets in the Gliese 832 system.” Alexander Weiss, the UTA Physics Chair, also lauded the achievement, saying: “This is an important breakthrough demonstrating the possible existence of a potential new planet orbiting a star close to our own. The fact that Dr. Satyal was able to demonstrate that the planet could maintain a stable orbit in the habitable zone of a red dwarf for more than 1 billion years is extremely impressive and demonstrates the world class capabilities of our department’s astrophysics group.” Another interesting tidbit is that this planet’s orbit would place it beyond or just within Gliese 832’s habitable zone. Whereas the Super-Earth Gliese 832c has an eccentric orbit that places it at the inner edge of this zone, this third planet would skirt its outer edge at the nearest. In this sense, Gliese 832’s two Super-Earths could very well be Venus-like and Mars-like in nature. Looking ahead, Dr. Satyal and his colleagues will be naturally be looking to confirm the existence of this planet, and other institutions are sure to conduct similar studies. This star system is yet another that is sure to be the subject of follow-up studies in the coming years, most likely from next-generation space telescopes like the James Webb Space Telescope. ### NASA’s Tracking Data Relay Satellite-M Vital for Science Relay Poised for Liftoff Aug. 18 – Watch Live The United Launch Alliance Atlas V rocket carrying NASA’s Tracking and Data Relay Satellite-M (TDRS-M) stands on the launch pad at Space Launch Complex 41 on Cape Canaveral Air Force Station poised for liftoff on Aug. 18, 2017. The rocket rolled out to the pad two days earlier on Aug. 16. Credit: Ken Kremer/kenkremer.com KENNEDY SPACE CENTER, FL – The last of NASA’s next generation Tracking and Data Relay Satellites (TRDS) that looks like a giant alien fish or cocooned creature but actually plays an absolutely vital role in relaying critical science measurements, research data and tracking observations gathered by the International Space Station (ISS), Hubble and a plethora of Earth science missions is poised for blastoff Friday, Aug. 18, morning from the Florida Space Coast. Liftoff atop a United Launch Alliance Atlas V rocket of NASA’s$408 million eerily insectoid-looking TDRS-M science relay comsat atop a United Launch Alliance (ULA) Atlas V rocket is scheduled to take place from Space Launch Complex 41 at Cape Canaveral Air Force Station at 8:03 a.m. EDT (2:03 GMT) Aug. 18.

Up close clean room visit with NASA’s newest science data relay comsat – Tracking and Data Relay Satellite-M (TDRS-M) inside the Astrotech payload processing facility high bay in Titusville, FL. Two gigantic fold out antennae’s, plus space to ground antenna dish visible inside the ‘cicada like cocoon’ with solar arrays below. Launch on ULA Atlas V slated for August 2017 from Cape Canaveral Air Force Station, Fl. Credit: Ken Kremer/kenkremer.com

The Atlas V/TDRS-M launch stack was rolled out from the ULA Vertical Integration Facility (VIF) to pad 41 Wednesday morning, Aug 16 starting at about 9:10 a.m. EDT. The quarter mile move took about 50 minutes and went off without a hitch.

“The spacecraft, Atlas V rocket and all range equipment are ready,” said NASA launch director Tim Dunn at today’s pre-launch news conference at the Kennedy Space Center. “And the combined government and contractor launch team is prepared to launch TDRS-M — a critical national space asset for space communications.”

The rocket and spacecraft sailed through the Flight Readiness Review (FRR) and Launch Ready Review (LRR) over the past few days conducted by NASA, ULA and Boeing and the contractor teams.

The two stage Atlas V rocket stands 191 feet tall.

The United Launch Alliance Atlas V rocket carrying NASA’s Tracking and Data Relay Satellite-M (TDRS-M) stands on the launch pad at Space Launch Complex 41 on Cape Canaveral Air Force Station poised for liftoff on Aug. 18, 2017. The rocket rolled out from the VIF the pad two days earlier on Aug. 16. Credit: Ken Kremer/kenkremer.com

You can witness the launch with you own eyes from many puiblic beaches, parks and spots ringing the Kennedy Space Center.

If you can’t personally be here to witness the launch in Florida, you can always watch NASA’s live coverage on NASA Television and the agency’s website.

The NASA/ULA/TDRS-M launch coverage will be broadcast on NASA TV beginning at 7:30 a.m. as the countdown milestones occur on Aug. 18 with additional commentary on the NASA launch blog:

You can watch the launch live at NASA TV at – http://www.nasa.gov/nasatv

The launch window opens at 8:03 a.m. EDT extends for 40 minutes from 8:03 a.m. to 8:43 a.m.

In the event of delay for any reason, the next launch opportunity is Saturday, Aug. 19 with NASA TV coverage starting about 7:30 a.m. EDT. The launch window opens at 7:59 a.m. EDT.

The United Launch Alliance Atlas V rocket carrying NASA’s Tracking and Data Relay Satellite-M (TDRS-M) stands on the launch pad at Space Launch Complex 41 on Cape Canaveral Air Force Station poised for liftoff on Aug. 18, 2017 The rocket rolled out to the pad two days earlier on Aug. 16. Credit: Ken Kremer/kenkremer.com

The weather looks quite good at this time with an 80% chance of favorable conditions at launch time according to U.S. Air Force meteorologists with the 45th Space Wing Weather Squadron at Patrick Air Force Base. The primary concerns on Aug. 18 are for thick clouds and cumulus clouds.

The odds remain at 80% favorable for the 24 hour scrub turnaround day on Aug. 19.

The launch was originally scheduled for Aug. 3 but was delayed a few weeks when the satellite’s Omni S-band antenna was damaged during final spacecraft closeout activities.

The Omni S-band antenna was bumped during final processing activities prior to the planned encapsulation inside the nosecone, said a Boeing official at the prelaunch media briefing and had to be replaced and then retested. It is critical to the opening phases of the mission for attitude control.

Inside the Astrotech payload processing facility in Titusville, FL,NASA’s massive, insect like Tracking and Data Relay Satellite, or TDRS-M, spacecraft is undergoing preflight processing during media visit on 13 July 2017. TDRS-M will transmit critical science data gathered by the ISS, Hubble and numerous NASA Earth science missions. It is being prepared for encapsulation inside its payload fairing prior to being transported to Launch Complex 41 at Cape Canaveral Air Force Station for launch on a United Launch Alliance (ULA) Atlas V rocket on 3 August 2017. Credit: Ken Kremer/kenkremer.com

The importance of the TDRS constellation of satellites can’t be overstated.

Virtually all the communications relay capability involving human spaceflight, such as the ISS, resupply vehicles like the SpaceX cargo Dragon and Orbital ATK Cygnus and the soon to launch human space taxis like crew Dragon, Boeing Starliner and NASA’s Orion deep space crew capsule route their science results voice, data, command, telemetry and communications via the TDRS network of satellites.

The TDRS constellation enables both space to space and space to ground communcations for virtually the entire orbital period.

Plus it’s a super busy time at the Kennedy Space Center. Because, if all goes well Friday’s launch will be the second this week!

The excitement of space travel got a big boost at the beginning of the week with the lunchtime blastoff of a SpaceX Falcon 9 and Dragon spacecraft on a cargo mission carrying 3 tons of science and supplies to the space station. Read my onsite articles here.

Blastoff of SpaceX Dragon CRS12 on its 12th resupply mission to the International Space Station from NASA’s Kennedy Space Center in Florida at 12:31 p.m. EDT on Monday, Aug. 14, 2017 as seen from the VAB roof. Credit: Ken Kremer/Kenkremer.com

The success of Monday’s SpaceX cargo Dragon rendezvous and berthing to the ISS is virtually entirely dependent on the TDRS network of satellites. That network will be enhanced with Fridays planned liftoff of NASA’s TDRS-M science relay comsat.

TDRS-M looks like a giant insect – or a fish depending on your point of view. It was folded into flight configuration for encapsulation in the clean room and the huge pair of single access antennas resembled a cocoon or a cicada. The 15 foot diameter single access antennas are large parabolic-style antennas and are mechanically steerable.

What does TDRS do? Why is it important? How does it operate?

“The existing Space Network of satellites like TDRS provide constant communications from other NASA satellites like the ISS or Earth observing satellites like Aura, Aqua, Landsat that have high bandwidth data that needs to be transmitted to the ground,” TDRS Deputy Project Manager Robert Buchanan explained to Universe Today during an interview in the Astrotech clean room.

“TRDS tracks those satellites using antennas that articulate. Those user satellites send the data to TDRS, like TDRS-M we see here and nine other TDRS satellites on orbit now tracking those satellites.”

“That data acquired is then transmitted to a ground station complex at White Sands, New Mexico. Then the data is sent to wherever those user satellites want the data to be sent is needed, such as a science data ops center or analysis center.”

The United Launch Alliance Atlas V rocket carrying NASA’s Tracking and Data Relay Satellite-M (TDRS-M) stands on the launch pad at Space Launch Complex 41 on Cape Canaveral Air Force Station poised for liftoff on Aug. 18, 2017. The rocket rolled out to the pad two days earlier on Aug. 16. Credit: Ken Kremer/kenkremer.com

TDRS-M, spacecraft, which stands for Tracking and Data Relay Satellite – M is NASA’s new and advanced science data relay communications satellite that will transmit research measurements and analysis gathered by the astronaut crews and instruments flying abroad the International Space Station (ISS), Hubble Space Telescope and over 35 NASA Earth science missions including MMS, GPM, Aura, Aqua, Landsat, Jason 2 and 3 and more.

The TDRS constellation orbits 22,300 miles above Earth and provide near-constant communication links between the ground and the orbiting satellites.

Tracking and Data Relay Satellite artwork explains how the TDRS constellation enables continuous, global communications coverage for near-Earth spacecraft. Credit: NASA

TRDS-M will have S-, Ku- and Ka-band capabilities. Ka has the capability to transmit as much as six-gigabytes of data per minute. That’s the equivalent of downloading almost 14,000 songs per minute says NASA.

The TDRS program is managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

TDRS-M is the third satellite in the third series of NASA’s American’s most powerful and most advanced Tracking and Data Relay Satellites. It is designed to last for a 15 year orbital lifetime.

The first TDRS satellite was deployed from the Space Shuttle Challenger in 1983 as TDRS-A.

TDRS-M was built by prime contractor Boeing in El Segundo, California and is the third of a three satellite series – comprising TDRS -K, L, and M. They are based on the Boeing 601 series satellite bus and will be keep the TDRS satellite system operational through the 2020s.

TDRS-K and TDRS-L were launched in 2013 and 2014.

The Tracking and Data Relay Satellite project is managed at NASA’s Goddard Space Flight Center.

TDRS-M was built as a follow on and replacement satellite necessary to maintain and expand NASA’s Space Network, according to a NASA description.

The gigantic satellite is about as long as two school buses and measures 21 meters in length by 13.1 meters wide.

It has a dry mass of 1800 kg (4000 lbs) and a fueled mass of 3,454 kilogram (7,615 lb) at launch.

TDRS-M will blastoff on a ULA Atlas V in the baseline 401 configuration, with no augmentation of solid rocket boosters on the first stage. The payload fairing is 4 meters (13.1 feet) in diameter and the upper stage is powered by a single-engine Centaur.

TDRS-M will be launched to a Geostationary orbit some 22,300 miles (35,800 km) above Earth.

“The final orbital location for TDRS-M has not yet been determined,” Buchanen told me.

The Atlas V booster was assembled inside the Vertical Integration Facility (VIF) at SLC-41 and was rolled out to the launch pad 2 days before liftoff with the TDRS-M science relay comsat comfortably encapsulated inside the nose cone.

Carefully secured inside its shipping container, the TDRS-M satellite was transported on June 23 by a US Air Force cargo aircraft from Boeing’s El Segundo, California facility to Space Coast Regional Airport in Titusville, Florida, for preflight processing at Astrotech.

Watch for Ken’s continuing onsite TDRS-M, CRS-12, ORS 5 and NASA and space mission reports direct from the Kennedy Space Center and Cape Canaveral Air Force Station, Florida.

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Learn more about the upcoming ULA Atlas TDRS-M NASA comsat on Aug. 18, 2017 , SpaceX Dragon CRS-12 resupply launch to ISS on Aug. 14, Solar Eclipse, NASA missions and more at Ken’s upcoming outreach events at Kennedy Space Center Quality Inn, Titusville, FL:

Aug 17-18: “TDRS-M NASA comsat, SpaceX CRS-12 resupply launches to the ISS, Intelsat35e, BulgariaSat 1 and NRO Spysat, SLS, Orion, Commercial crew capsules from Boeing and SpaceX , Heroes and Legends at KSCVC, ULA Atlas/John Glenn Cygnus launch to ISS, SBIRS GEO 3 launch, GOES-R weather satellite launch, OSIRIS-Rex, Juno at Jupiter, InSight Mars lander, SpaceX and Orbital ATK cargo missions to the ISS, ULA Delta 4 Heavy spy satellite, Curiosity and Opportunity explore Mars, Pluto and more,” Kennedy Space Center Quality Inn, Titusville, FL, evenings

### NASA Plans to Send CubeSat To Venus to Unlock Atmospheric Mystery

From space, Venus looks like a big, opaque ball. Thanks to its extremely dense atmosphere, which is primarily composed of carbon dioxide and nitrogen, it is impossible to view the surface using conventional methods. As a result, little was learned about its surface until the 20th century, thanks to development of radar, spectroscopic and ultraviolet survey techniques.

Interestingly enough, when viewed in the ultraviolet band, Venus looks like a striped ball, with dark and light areas mingling next to one another. For decades, scientists have theorized that this is due to the presence of some kind of material in Venus’ cloud tops that absorbs light in the ultraviolet wavelength. In the coming years, NASA plans to send a CubeSat mission to Venus in the hopes of solving this enduring mystery.

The mission, known as the CubeSat UV Experiment (CUVE), recently received funding from the Planetary Science Deep Space SmallSat Studies (PSDS3) program, which is headquartered as NASA’s Goddard Space Flight Center. Once deployed, CUVE will determine the composition, chemistry, dynamics, and radiative transfer of Venus’ atmosphere using ultraviolet-sensitive instruments and a new carbon-nanotube light-gathering mirror.

Ultraviolet image of Venus taken by NASA’s Pioneer-Venus Orbiter in 1979, lending Venus a striped, light and dark appearance. Credit: NASA

The mission is being led by Valeria Cottini, a researcher from the University of Maryland who is also CUVE’s Principle Investigator (PI). In March of this year, NASA’s PSDS3 program selected it as one of 10 other studies designed to develop mission concepts using small satellites to investigate Venus, Earth’s moon, asteroids, Mars and the outer planets.

Venus is of particular interest to scientists, given the difficulties of exploring its thick and hazardous atmosphere. Despite the of NASA and other space agencies, what is causing the absorption of ultra-violet radiation in the planet’s cloud tops remains a mystery. In the past, observations have shown that half the solar energy the planet receives is absorbed in the ultraviolet band by the upper layer of its atmosphere – the level where sulfuric-acid clouds exist.

Other wavelengths are scattered or reflected into space, which is what gives the planet its yellowish, featureless appearance. Many theories have been advanced to explain the absorption of UV light, which include the possibility that an absorber is being transported from deeper in Venus’ atmosphere by convective processes. Once it reaches the cloud tops, this material would be dispersed by local winds, creating the streaky pattern of absorption.

The bright areas are therefore thought to correspond to regions that do not contain the absorber, while the dark areas do. As Cottini indicated in a recent NASA press release, a CubeSat mission would be ideal for investigating these possibilities:

“Since the maximum absorption of solar energy by Venus occurs in the ultraviolet, determining the nature, concentration, and distribution of the unknown absorber is fundamental. This is a highly-focused mission – perfect for a CubeSat application.”

Such a mission would leverage recent improvements in miniaturization, which have allowed for the creation of smaller, box-sized satellites that can do the same jobs as larger ones. For its mission, CUVE would rely on a miniaturized ultraviolet camera and a miniature spectrometer (allowing for analysis of the atmosphere in multiple wavelengths) as well as miniaturized navigation, electronics, and flight software.

Another key component of the CUVE mission is the carbon nanotube mirror, which is part of a miniature telescope the team is hoping to include. This mirror, which was developed by Peter Chen (a contractor at NASA Goddard), is made by pouring a mixture of epoxy and carbon nanotubes into a mold. This mold is then heated to cure and harden the epoxy, and the mirror is coated with a reflective material of aluminum and silicon dioxide.

In addition to being lightweight and highly stable, this type of mirror is relatively easy to produce. Unlike conventional lenses, it does not require polishing (an expensive and time-consuming process) to remain effective. As Cottini indicated, these and other developments in CubeSat technology could facilitate low-cost missions capable of piggy-backing on existing missions throughout the Solar System.

“CUVE is a targeted mission, with a dedicated science payload and a compact bus to maximize flight opportunities such as a ride-share with another mission to Venus or to a different target,” she said. “CUVE would complement past, current, and future Venus missions and provide great science return at lower cost.”

A cubesat structure, 1U in size. Credit: Wikipedia Commons/Svobodat

The team anticipates that in the coming years, the probe will be sent to Venus as part of a larger mission’s secondary payload. Once it reaches Venus, it will be launched and assume a polar orbit around the planet. They estimate that it would take CUVE one-and-a-half years to reach its destination, and the probe would gather data for a period of about six months.

If successful, this mission could pave the way for other low-cost, lightweight satellites that are deployed to other Solar bodies as part of a larger exploration mission. Cottini and her colleagues will also be presenting their proposal for the CUVE satellite and mission at the 2017 European Planetary Science Congress, which is being held from September 17th – 22nd in Riga, Latvia.

### Gravitational Lensing Provides Rare Glimpse Into Interiors of Black Holes

The observable Universe is an extremely big place, measuring an estimated 91 billion light-years in diameter. As a result, astronomers are forced to rely on powerful instruments to see faraway objects. But even these are sometimes limited, and must be paired with a technique known as gravitational lensing. This involves relying on a large distribution of matter (a galaxy or star) to magnify the light coming from a distant object.

Using this technique, an international team led by researchers from the California Institute of Technology’s (Caltech) Owens Valley Radio Observatory (OVRO) were able to observe jets of hot gas spewing from a supermassive black hole in a distant galaxy (known as PKS 1413 + 135). The discovery provided the best view to date of the types of hot gas that are often detected coming from the centers of supermassive black holes (SMBH).

The research findings were described in two studies that were published in the August 15th issue of The Astrophysical Journal. Both were led by Harish Vedantham, a Caltech Millikan Postdoctoral Scholar, and were part of an international project led by Anthony Readhead – the Robinson Professor of Astronomy, Emeritus, and director of the OVRO.

The Owens Valley Radio Observatory (OVRO) – located near Bishop, California – is one of the largest university-operated radio observatories in the world. Credit: ovro.caltech.edu

This OVRO project has been active since 2008, conducting twice-weekly observations of some 1,800 active SMBHs and their respective galaxies using its 40-meter telescope. These observations have been conducted in support of NASA’s Fermi Gamma-ray Space Telescope, which has be conducting similar studies of these galaxies and their SMBHs during the same period.

As the team indicated in their two studies, these observations have provided new insight into the clumps of matter that are periodically ejected from supermassive black holes, as well as opening up new possibilities for gravitational lensing research. As Dr. Vedantham indicated in a recent Caltech press statement:

“We have known about the existence of these clumps of material streaming along black hole jets, and that they move close to the speed of light, but not much is known about their internal structure or how they are launched. With lensing systems like this one, we can see the clumps closer to the central engine of the black hole and in much more detail than before.”

While all large galaxies are believed to have an SMBH at the center of their galaxy, not all have jets of hot gas accompanying them. The presence of such jets are associated with what is known as an Active Galactic Nucleus (AGN), a compact region at the center of a galaxy that is especially bright in many wavelengths – including radio, microwave, infrared, optical, ultra-violet, X-ray and gamma ray radiation.

Illustration showing the likely configuration of a gravitational lensing system discovered by OVRO. Credit: Anthony Readhead/Caltech/MOJAVE

These jets are the result of material that is being pulled towards an SMBH, some of which ends up being ejected in the form of hot gas. Material in these streams travels at close to the speed of light, and the streams are active for periods ranging from 1 to 10 million years. Whereas most of the time, the jets are relatively consistent, every few years, they spit out additional clumps of hot matter.

Back in 2010, the OVRO researchers noticed that PKS 1413 + 135’s radio emissions had brightened, faded and then brightened again over the course of a year. In 2015, they noticed the same behavior and conducted a detailed analysis. After ruling out other possible explanations, they concluded that the overall brightening was likely caused by two high-speed clumps of material being ejected from the black hole.

These clumps traveled along the jet and became magnified when they passed behind the gravitational lens they were using for their observations. This discovery was quite fortuitous, and was the result of many years of astronomical study. As Timothy Pearson, a senior research scientist at Caltech and a co-author on the paper, explained:

“It has taken observations of a huge number of galaxies to find this one object with the symmetrical dips in brightness that point to the presence of a gravitational lens. We are now looking hard at all our other data to try to find similar objects that can give a magnified view of galactic nuclei.”

Artist’s representation of an active galactic nucleus (AGN) at the center of a galaxy. Credit: NASA/CXC/M.Weiss

What was also exciting about the international team’s observations was the nature of the “lens” they used. In the past, scientists have relied on massive lenses (i.e. entire galaxies) or micro lenses that consisted of single stars. However, the team led by Dr. Vedantham and Dr. Readhead relied on an what they describe as a “milli-lens” of about 10,000 solar masses.

This could be the first study in history that relied on an intermediate-sized lens, which they believe is most likely a star cluster. One of the advantages of a milli-sized lens is that it is not large enough to block out the entire source of light, making it easier to spot smaller objects. With this new gravitational lensing system, it is estimated that astronomers will be able to observe clumps at scales about 100 times smaller than before. As Readhead explained:

“The clumps we’re seeing are very close to the central black hole and are tiny – only a few light-days across. We think these tiny components moving at close to the speed of light are being magnified by a gravitational lens in the foreground spiral galaxy. This provides exquisite resolution of a millionth of a second of arc, which is equivalent to viewing a grain of salt on the moon from Earth.”

What’s more, the researchers indicate that the lens itself is of scientific interest, for the simple reason that not much is known about objects in this mass range. This potential star cluster could therefore act as a sort of laboratory, giving researchers a chance to study gravitational milli-lensing while also providing a clear view of the nuclear jets streaming from active galactic nuclei.

Image of the 40-meter telescope of the Owens Valley Radio Observatory (OVRO), located near Bishop, California. Credit: Anthony Readhead/Caltech

Looking ahead, the team hopes to confirm the results of their studies using another technique known as Very-Long Baseline Interferometry (VLBI). This will involve radio telescopes from around the world taking detailed images of PKS 1413 + 135 and the SMBH at its center. Given what they have observed so far, it is likely that this SMBH will spit out another clump of matter in a few years time (by 2020).

Vedantham, Readhead and their colleagues plan to be ready for this event. Spotting this next clump would not only validate their recent studies, it would also validate the milli-lens technique they used to conduct their observations. As Readhead indicated, “We couldn’t do studies like these without a university observatory like the Owens Valley Radio Observatory, where we have the time to dedicate a large telescope exclusively to a single program.”

### Prelude to Totality: A Final Look at the Total Solar Eclipse

Totality! The view during the November 2012 total solar eclipse. Image credit and copyright: Sharin Ahmad (@Shahgazer)

It’s hard to believe: we’re now just one short weekend away from the big ticket astronomical event for 2017, as a total solar eclipse is set to cross over the contiguous United States on Monday, August 21 st .

Celestial mechanics is a sure thing in this Universe, a certainty along with death and taxes that you can bet on. But there are still a few key question marks leading up to eclipse day, things that we can now finally make intelligent assumptions about a few days out.

Although totality slices through the U.S., partial phases of the eclipse touch on every continent except Antarctica and Australia. Credit: Michael Zeiler/The Great American Eclipse.

First up is solar activity. If you’re like us, you’ll be showing off the Sun in both visible and hydrogen alpha as the Moon begins making its slow hour long creep across the disk of Sol. First, the good news: sunspot active region AR 2671 made its Earthward debut on Tuesday August 15 th , and will most likely stick around until eclipse day. The bad news is, it most likely won’t have lots of friends, as solar cycle #24 begins its long slow ebb towards the solar minimum in 2019-2020. Likewise, I wouldn’t expect to see any magnificent sprouting red prominences in the solar chromosphere in the seconds bracketing totality, though we could always be pleasantly surprised.

The Earthward face of Sol as of August 17, four days before totality. Sunspot AR 2671 is robust and growing in complexity. Credit: NASA/SDO/HMI

How will the white hot corona appear during totality? This is the signature climax of any total solar eclipse: veteran umbraphiles can actually glance at a photo of totality and tell you which eclipse it was from, just on the shape of the corona. The National Solar Observatory released a model of what that Sun’s magnetosphere was doing one Carrington rotation (27 days) prior to the eclipse on July 25th, a pretty good predictor of the corona might look like during those fleeting moments of totality:

The shape of the field lines of the solar corona, one rotation prior to the August 21st total solar eclipse. Credit: The National Solar Observatory.

NASA will be chasing the umbra of the Moon with two converted W-57 aircraft during the eclipse, hoping to unlock the “coronal heating paradox,” image Mercury in the infrared, and hunt for elusive Vulcanoid asteroids near the eclipsed Sun.

The view of the corona during totality? This computational model was derived from NASA SDO data during the last solar rotation. Credit: Predictive Science Inc.

The corona is about twice as bright as a Full Moon, and its interface with the solar wind extends out past the Earth. The very onset of totality is like the footstep of a giant passing over the landscape, as the door of reality is suddenly ripped open, revealing the span of the glittering solar system at midday. Keep your eyes peeled for Mercury, Venus, Mars, Jupiter and twinkling Regulus tangled up in the corona, just a degree from the Sun-Moon pair:

The line up of the planets, bright stars and the eclipsed Sun during totality at 2:37 PM EDT as seen from Franklin, North Carolina. Credit: Stellarium.

Also, be sure to scan the local horizon for a strange 360 degree sunset as you stand in the umbra of the Moon. An “eclipse wind” may kick up, as temperatures plummet and nature is fooled by the false dawn, causing chickens to come home to roost and nocturnal animals to awaken. I dare you to blink. Totality can affect the human heart as well, causing tears to cries of surprise.

Here’s an interesting, though remote, possibility. Could a sungrazing “eclipse comet” photo bomb the show? Karl Battams (@SungrazerComets) raises this question on a recent Planetary Society blog post. Battams works with the Solar Heliospheric Observatory (SOHO), which has discovered an amazing 3,358 comets crossing the field of view of its LASCO imagers since 1995. Comets have been discovered during eclipses before, most notably in 1882 and 1948. To be sure, it’s a remote possibility this late in the game, but Battams promises to give us one last quick look via SOHO the morning of the eclipse on his Twitter feed to see if any cometary interlopers are afoot.

The possible search area for Kreutz group sungrazers during the August 21st eclipse. Credit: Karl Battams.

Now, on to the biggest question mark going into this eclipse weekend: what’s the weather going to be like during the eclipse? This is the ever-dominating factor on everyone’s mind leading up to eclipse day. Keep in mind, the partial phases are long even a partly cloudy sky will afford occasional glimpses of the Sun during the partial phases of an eclipse. Totality, however, is fleeting – 2 minutes and 40 seconds near Hopkinsville, Kentucky and less for most – meaning even a solitary cumulus cloud drifting across the Sun at the wrong moment can spoil the view. No weather model can predict the view of the sky to that refined a level. And while best bets are still out west, lingering forest fires in Oregon are a concern, along early morning fog on the western side of the Cascade Mountains. Michael Zeiler over at The Great American Eclipse has been providing ESRI models of the cloud cover over the eclipse path for Monday… here’s the outlook as of Thursday, August 17 th :

A look at cloud cover prospects over the eclipse path as of August 17. Credit: Michael Zeiler/Great American Eclipse/ESRI.

Computer models should begin to come into agreement this weekend, a good sign that we know what the weather is going to do Monday. Needless to say, a deviation from the standard climate models could send lots of folks scrambling down the path at the last minute… I’ve heard of folks with up to 5 (!) separate reservations along the path of totality, no lie…

The NOAA also has a fine site dedicated to weather and cloud coverage across the path come eclipse day, and Skippy Sky is another great resource aimed at sky viewing and cloud cover.

Clouded out? The good folks at the Virtual Telescope have got you covered, with a webcast for the total solar eclipse starting at 17:00 UT/1:00 PM EDT:

Credit: The Virtual Telescope Project.

Of course, you’ll need to use proper solar viewing methods during all partial phases of the eclipse. This means either using a telescope with a filter specifically designed to look at the Sun, a pin hole projector, or certified ISO 12312-2 eclipse glasses. If you’ve got an extra pair, why not convert them into a safe filter for those binoculars or a small telescope as well:

Also be wary of heatstroke, standing out showing folks the partially eclipsed Sun for an hour or more. It is August, and heat exhaustion can come on in a hurry. Be sure you have access to shade and stay cool and hydrated in the summer Sun.

Finally, eyes from space will be watching the eclipse from the International Space Station as well. Looking out at Monday, the ISS will pass through the penumbra of the Moon and see partial phases of the eclipse three times centered on 16:32, 18:20, and 20:00 Universal Time. The center time is particularly intriguing, as astros have a chance to see the dark umbral shadow of the Moon crossing the central U.S. This also means that eclipse viewers on planet Earth around southern Illinois might want to glance northward briefly, to spy the ISS during totality. Also, viewers along a line along southern central Canada will have a chance to catch an ISS transit across the face of the partially eclipsed Sun around the same time. Check CALSky for details.

Three passes of the International Space Station versus the path of of totality. The inset shows the view of the partially eclipsed Sun as seen from the ISS. Credit: NASA/JSC.

We’ll be at the Pisgah Astronomical Research Institute in southwestern North Carolina, for a glorious 104 seconds of totality. We expect to be out of wifi range come eclipse day, but we’ll tweet out key eclipse milestones as @Astroguyz. We also plan on writing up the eclipse experience with state-by-state testimonials post eclipse.

Perhaps, the August 21st total solar eclipse will bring us all together for one brief moment, to witness the grandest of astronomical spectacles. We’re lucky to share a small patch of time and space where total solar eclipses are possible. Good luck, clear skies, and see you on the other side early next week!

• Read more about the August 21 st total solar eclipse and the true tale of Edison’s chickens and the 1878 eclipse in our free e-book: 101 Astronomical Events for 2017.
• The oldest video featuring totality? Read the mystery of the August 21 st , 1914 over war torn Europe and this amazing video over Sweden.
• Eclipse… sci-fi? Read our original eclipse-fueled talesExeligmos, Shadowfall, Peak Season and more.
• Read our CNN Op-Ed, Why We Chase Eclipses.

### Can Astronauts See Stars From the Space Station?

I’ve often been asked the question, “Can the astronauts on the Space Station see the stars?” Astronaut Jack Fischer provides an unequivocal answer of “yes!” with a recent post on Twitter of a timelapse he took from the ISS. Fischer captured the arc of the Milky Way in all its glory, saying it “paints the heavens in a thick coat of awesome-sauce!”

Can you see stars from up here? Oh yeah baby! Check out the Milky Way as it spins & paints the heavens in a thick coat of awesome-sauce! pic.twitter.com/MsXeNHPxLF

&mdash Jack Fischer (@Astro2fish) August 16, 2017

But, you might be saying, “how can this be? I thought the astronauts on the Moon couldn’t see any stars, so how can anyone see stars in space?”

John W. Young on the Moon during Apollo 16 mission. Charles M. Duke Jr. took this picture. The LM Orion is on the left. April 21, 1972. Credit: NASA
It is a common misconception that the Apollo astronauts didn’t see any stars. While stars don’t show up in the pictures from the Apollo missions, that’s because the camera exposures were set to allow for good images of the bright sunlit lunar surface, which included astronauts in bright white space suits and shiny spacecraft. Apollo astronauts reported they could see the brighter stars if they stood in the shadow of the Lunar Module, and also they saw stars while orbiting the far side of the Moon. Al Worden from Apollo 15 has said the sky was “awash with stars” in the view from the far side of the Moon that was not in daylight.

Just like stargazers on Earth need dark skies to see stars, so too when you’re in space.

The cool thing about being in the ISS is that astronauts experience nighttime 16 times a day (in 45 minute intervals) as they orbit the Earth every 90 minutes, and can have extremely dark skies when they are on the “dark” side of Earth. Here’s another recent picture from Fischer where stars can be seen:

Twinkle, twinkle, little star…
Up above the world so high
Like a diamond in the sky… pic.twitter.com/8H7CshyP0p

&mdash Jack Fischer (@Astro2fish) August 13, 2017

For stars to show up in any image, its all about the exposure settings. For example, if you are outside (on Earth) on a dark night and can see thousands of stars, if you just take your camera or phone camera and snap a quick picture, you’ll just get a darkness. Earth-bound astrophotographers need long-exposure shots to capture the Milky Way. Same is true with ISS astronauts: if they take long-exposure shots, they can get stunning images like this one:

This long exposure image of the night sky over Earth was taken on August 9, 2015 by a member of the Expedition 44 crew on board the International Space Station. Credit: NASA.

This image, set to capture the bright solar arrays and the rather bright Earth (even though its in twilight) reveals no stars:

Sometimes you look out the window and it just takes your breath away from how beautiful Earth is. Today is one of those times… #EarthShapes pic.twitter.com/53UqL9BFH1

&mdash Jack Fischer (@Astro2fish) August 2, 2017

In this timelapse of Earth at night, a few stars show up, but again, the main goal here was to have the camera capture the Earth:

Universe Today’s Bob King has a good, detailed explanation of how astronauts on the ISS can see stars on his Astro Bob blog Astrophysicist . Brian Koberlein explains it on his blog, here.

You can check out all the images that NASA astronauts take from the ISS on the “Astronaut Photography of Earth” site, and almost all the ISS astronauts and cosmonauts have social media accounts where they post pictures. Jack Fischer, currently on board, tweets great images and videos frequently here.

### Station Crew Grapples SpaceX Dragon Delivering Tons of Science After Thunderous Liftoff: Launch & Landing Gallery

The SpaceX Dragon CRS-12 cargo craft is now attached to the International Space Station after arriving on Aug. 16, 2017. It delivered over 3 tons of science and supplies to the six person Expedition 52 crew. Credit: NASA TV

KENNEDY SPACE CENTER, FL – Following a two day orbital chase and ballet of carefully choreographed thruster firings, the SpaceX Dragon cargo capsule launched at lunchtime on Monday Aug. 14 with tons of science and supplies arrived in the vicinity of the International Space Station (ISS) this morning, Wednesday, Aug 16.

While Dragon maneuvered in ever so slowly guided by lasers, NASA astronaut Jack Fischer and ESA (European Space Agency) astronaut Paolo Nespoli carefully extended the stations robotic arm to reach out and grapple the gumdrop shaped capsule.

They deftly captured the Dragon CRS-12 resupply spacecraft slightly ahead of schedule at 6:52 a.m. EDT with the station’s 57.7-foot-long (17.6 meter-long) Canadian-built robotic arm while working at a robotics work station in the seven windowed domed Cupola module.

The SpaceX Dragon cargo craft is pictured approaching the International Space Station on Wednesday morning Aug. 16, 2017. Credit: NASA

The million pound orbiting outpost was traveling over the Pacific Ocean north of New Zealand at the time of capture.

Liftoff of the SpaceX Falcon 9 took place precisely on time 2 days earlier with ignition of the 9 Merlin 1D first stage engines from seaside pad 39A at NASA’s Kennedy Space Center in Florida today (Aug. 14) at 12:31 p.m. EDT (1631 GMT).

SpaceX launched its 12th resupply mission to the International Space Station from NASA’s Kennedy Space Center in Florida at 12:31 p.m. EDT on Monday, Aug. 14, 2017. Credit: Ken Kremer/Kenkremer.com

The two stage Falcon 9 stands 213-foot-tall (65-meter-tall). The combined output of the 9 Merlin 1D first stage engines generates 1.7 million pounds of liftoff thrust, fueled by liquid oxygen and RP-1 propellants.

SpaceX launched its 12th resupply mission to the International Space Station from NASA’s Kennedy Space Center in Florida at 12:31 p.m. EDT on Monday, Aug. 14, 2017. Credit: Ken Kremer/Kenkremer.com

See an exciting gallery of launch imagery and videos including the thrilling ground landing of the 156 foot tall first stage booster back at Cape Canaveral at Landing Zone-1 – from this author and several space colleagues.

SpaceX launched its 12th resupply mission to the International Space Station from NASA’s Kennedy Space Center in Florida at 12:31 p.m. EDT on Monday, Aug. 14, 2017. Credit: Ken Kremer/Kenkremer.com

Monday’s picture perfect lunchtime liftoff of the unmanned SpaceX CRS-12 Dragon cargo freighter bound for the ISS and loaded with over 3 tons of science, research hardware and supplies including a hefty cosmic ray detector named ISS-CREAM, medical research experiments dealing with Parkinson’s disease, lung and heart tissue, vegetable seeds, dozens of mice and much more – came off without a hitch.

Ground controllers then carried out the remainder of the work to berth the SpaceX Dragon cargo spacecraft at the Earth facing port on the Harmony module of the International Space Station at 9:07 a.m. EDT.

This illustration of the International Space Station shows the current configuration with four visiting vehicle spaceships parked at the space station including the SpaceX Dragon CRS-12 cargo craft that arrived Aug. 16, 2017, the Progress 67 resupply ship and two Soyuz crew ships. Credit: NASA

The crew was perhaps especially eager for this Dragons arrival because tucked inside the more than 3 tons of cargo was a stash of delicious ice cream treats.

“The small cups of chocolate, vanilla and birthday cake-flavored ice cream are arriving in freezers that will be reloaded with research samples for return to Earth when the Dragon spacecraft departs the station mid-September,” said NASA.

Indeed the crew did indeed open the hatches today, early than planned, a few hours after arrival and completion of the requisite safety and leak checks.

The SpaceX Dragon cargo craft is pictured approaching the International Space Station on Wednesday morning Aug. 16, 2017. Credit: NASA TV

The whole sequence was broadcast on NASA TV that began live arrival coverage at 5:30 a.m showing numerous stunning video sequences of the rendezvous and grappling often backdropped by our precious Home Planet.

The current multinational Expedition 52 crew serving aboard the ISS comprises of Flight Engineers Paolo Nespoli from ESA, Jack Fischer, Peggy Whitson and Randy Bresnik of NASA and Sergey Ryazanskiy and Commander Fyodor Yurchikhin of Roscosmos.

Launch of SpaceX Falcon on Dragon CRS-12 mission to the ISS from NASA’s Kennedy Space Center in Florida at 12:31 p.m. EDT on Monday, Aug. 14, 2017. Credit: Julian Leek

The Dragon resupply ship dubbed Dragon CRS-12 counts as SpaceX’s twelfth contracted commercial resupply services (CRS) mission to the International Space Station for NASA since 2012.

SpaceX holds a NASA commercial resupply services (CRS) contract that includes up to 20 missions under the original CRS-1 contract.

The 20-foot high, 12-foot-diameter Dragon CRS-12 vessel is carrying more than 6,400 pounds ( 2,900 kg) of science experiments and research instruments, crew supplies, food water, clothing, hardware, gear and spare parts to the million pound orbiting laboratory complex. 20 mice are also onboard. This will support dozens of the 250 research investigations and experiments being conducted by Expedition 52 and 53 crew members.

The Expedition 52 crew poses for a unique portrait. Pictured clockwise from top right are, Flight Engineers Paolo Nespoli, Jack Fischer, Peggy Whitson, Sergey Ryazanskiy, Randy Bresnik and Commander Fyodor Yurchikhin. Credit: NASA/Roscosmos/ESA

Video Caption: CRS-12 launch from Pad 39A on a Falcon 9 rocket. Pad camera views from the launch of the CRS-12 mission carrying 6415 pounds of supplies and equipment to the International Space Station on August 14, 2017. Credit: Jeff Seibert

The SpaceX Falcon 9/Dragon CRS-12 launch was the first of a rapid fire sequence of a triad of launches along the Florida Space Coast over the next 11 days of manmade wonder – Plus a Total Solar ‘Eclipse Across America’ natural wonder sandwiched in between !!

Launch of SpaceX Falcon on Dragon CRS-12 mission to the ISS from NASA’s Kennedy Space Center in Florida at 12:31 p.m. EDT on Monday, Aug. 14, 2017. Credit: Julian Leek

Watch for Ken’s continuing onsite CRS-12, TRDS-M, and ORS 5 and NASA mission reports direct from the Kennedy Space Center and Cape Canaveral Air Force Station, Florida.

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Ground landing of SpaceX Falcon 9 first stage at Landing Zone-1 (LZ-1) after SpaceX launched its 12th resupply mission to the International Space Station from NASA’s Kennedy Space Center in Florida from pad 39A at 12:31 p.m. EDT on Monday, Aug. 14, 2017. Credit: Ken Kremer/Kenkremer.com

Learn more about the upcoming ULA Atlas TDRS-M NASA comsat on Aug. 18, 2017 , SpaceX Dragon CRS-12 resupply launch to ISS on Aug. 14, Solar Eclipse, NASA missions and more at Ken’s upcoming outreach events at Kennedy Space Center Quality Inn, Titusville, FL:

Aug 17-18: “TDRS-M NASA comsat, SpaceX CRS-12 resupply launches to the ISS, Intelsat35e, BulgariaSat 1 and NRO Spysat, SLS, Orion, Commercial crew capsules from Boeing and SpaceX , Heroes and Legends at KSCVC, ULA Atlas/John Glenn Cygnus launch to ISS, SBIRS GEO 3 launch, GOES-R weather satellite launch, OSIRIS-Rex, Juno at Jupiter, InSight Mars lander, SpaceX and Orbital ATK cargo missions to the ISS, ULA Delta 4 Heavy spy satellite, Curiosity and Opportunity explore Mars, Pluto and more,” Kennedy Space Center Quality Inn, Titusville, FL, evenings

Ground landing of SpaceX Falcon 9 first stage at Landing Zone-1 (LZ-1) after SpaceX launched its 12th resupply mission to the International Space Station from NASA’s Kennedy Space Center in Florida from pad 39A at 12:31 p.m. EDT on Monday, Aug. 14, 2017. Credit: Ken Kremer/Kenkremer.com Blastoff of SpaceX Dragon CRS12 on its 12th resupply mission to the International Space Station from NASA’s Kennedy Space Center in Florida at 12:31 p.m. EDT on Monday, Aug. 14, 2017 as seen from the VAB roof. Credit: Ken Kremer/Kenkremer.com Blastoff of SpaceX Dragon CRS12 on its 12th resupply mission to the International Space Station from NASA’s Kennedy Space Center in Florida at 12:31 p.m. EDT on Monday, Aug. 14, 2017 as seen from the VAB roof. Credit: Ken Kremer/Kenkremer.com Blastoff of SpaceX Dragon CRS12 on its 12th resupply mission to the International Space Station from NASA’s Kennedy Space Center in Florida at 12:31 p.m. EDT on Monday, Aug. 14, 2017 as seen from the VAB roof. Credit: Ken Kremer/Kenkremer.com