# Would the Event Horizon Telescope be able to produce a superior image of Betelgeuse?

Current images of Betelgeuse are already amazing, but I was wondering if the EHT could be able to make a significantly better image, given that Betelgeuse is pretty big and pretty bright?

Presumably, yes, EHT observations could improve on existing radio observations of Betelgeuse (e.g. recent ALMA images and comparatively ancient VLA images). Any observations would likely be targeted at known photospheric mm or super-mm emission from the star, mapping radius and temperature changes. The ALMA data showed the existence of a spot $$sim1000$$ K hotter than neighboring regions, which would ideally teach us something about convection inside the star.

With a (current) resolution of a couple tens of microarcseconds at $$lambdasim1.3$$ mm, the EHT would indeed improve on existing interferometer results by orders of magnitude (which I believe, in the case of ALMA, are the highest-resolution images of Betelgeuse, period, at any wavelength).

## Event Horizon Telescope

The EHT consortium consists of 14 institutes with about 200 participants in Europe, Asia, Africa and America. Chair of the EHT interim board is Prof. J. Anton Zensus from the Max Planck Institute for Radio Astronomy (MPIfR), Director of the EHT is Dr. Shepherd S. Doeleman (Harvard & MIT, USA).

The research department of Prof. Michael Kramer at MPIfR is participating via the „BlackHoleCam“ (BHC) project, founded by the European Research Council (ERC), in collaboration with Prof. Heino Falcke (Radboud University Nijmegen, The Netherlands) and Prof. Luciano Rezzolla (Frankfurt University, Germany).

The technique applied for the EHT observations is called Very Long Baseline Interferometry (VLBI). VLBI enables the highest resolutions in astronomy by coupling a number of radio telecopes distributed across different countries on Earth. This method is used for the investigation of the direct environment of supermassive black holes in active galactic nuclei, in particular jets of high-energy particles emitted from the central regions. In the framework of the EHT project it will become possible to directly image the central black holes in addition to the jets. This is achieved by observations at shorter radio waves of only 1.3 mm wavelength. The resolution of the world-wide network of radio telescopes at that wavelength corresponds to a magnification factor of two million or the size of a tennis ball in the distance of the moon.

To minimize the impact of the Earth’s atmosphere at that wavelength, the observations are only possible at high-altitude dry sites like the Atacama desert in Chile, the Sierra Nevada in southern Spain, high volcanoes at Hawaii or even the South Pole.

Including the Atacama Large Millimeter Arrays (ALMA) with its 64 dishes in total provides a very high sensitivity. In total it is synthesizing a radio telescope with an equivalent diameter of 84 meters, superior to the usual Millimeter-wave radio telescopes with 15 to 30 meters in diameter. After a preparation phase of several years observations within the EHT project will now take place between April 04 and April 14 this year (see below).

VLBI data sets are analyzed in dedicated super computers, the so-called correlators. For the analysis of the EHT observations two correlators will be used, at the Max Planck Institute for Radio Astronomy in Bonn (Head of the Correlator group: Walter Alef) and at Haystack Observatory in Haystack, Massachusetts, USA.

For an overall picture of the physics of black holes the observations are complemented by numerical simulations and tests with synthetical data.

The obervations are co-financed by the European ERC project BlackHoleCam (BHC) and supported among others by Max Planck Society.

As a part of the BHC project, MPIfR scientists are searching for pulsars in the direct neighbourhood of the black hole in the centre of the Milky Way in order to establish independent measurements of its properties.

Before the start of the EHT observations, the Global Millimetre-VLBI Array (GMVA) network will perform observations at 3 mm wavelength with 14 antennas from March 31 to April 04, focusing on several active galaxies. Three of those targets will be observed jointly with the ALMA telescope in Chile. The 100-m radio telescope in Effelsberg will participate in the GMVA observations. The analysis of the GMVA observations including phased ALMA will be completely postprocessed at the MPIfR correlator in Bonn.

## How Was The Image Taken?

X-ray emission measured with CHANDRA, against EHT’s image. Credit: X-ray: NASA/CXC/Villanova University/J. Neilsen Radio: Event Horizon Telescope Collaboration

8 Telescopes that make up the Event Horizon Telescope (EHT) were used to take this image, using Very Long Baseline Interferometry (VLBI) to create an Earth-sized telescope with incredibly high resolution. Customising and connecting telescopes for VLBI takes years to execute, but EHT and CHANDRA succeeded! The image was taken in 2017, but was published on the 10th of April 2019.

The image couldn’t be taken like a normal photo. The telescopes used were radio telescopes, and produced raw data which needed to be analysed using multiple algorithms.

Katie Bouman, doctor in electrical engineering and computer science, started writing the algorithms as a graduate. Eventually she lead a team to complete the algorithm, taking over three years to finish.

Dr Bouman and the huge amount of hard-drives flown in from all 8 telescopes! Amazing work!

An amazing achievement and huge leap forward in science!

## The First Image Of A Black Hole's Magnetic Fields

A view of M87's supermassive black hole in polarized light. The lines mark the orientation of polarization, which is related to the magnetic field around the shadow of the black hole. CREDIT EHT Collaboration

Astronomers have now obtained a new view of the supermassive black hole at the center of galaxy M87. Images released today by the Event Horizon Telescope (EHT) collaboration reveal how the black hole, some 55 million light-years away, appears in polarized light.

The image marks the first time astronomers have captured and mapped polarization, a sign of magnetic fields, so close to the edge of a black hole.

Scientists still don't understand how magnetic fields -- areas where magnetism affects how matter moves -- influence black hole activity. Do they help direct matter into the hungry mouths of black holes? Can they explain the mysterious jets of energy that extend out of the galaxy's core?

In two studies published today in the Astrophysical Journal Letters, EHT astronomers reveal their latest findings and how magnetic fields may be influencing the black hole at the center of M87.

"One of the main science drivers of the EHT is distinguishing different magnetic field configurations around the black hole," says Angelo Ricarte, a co-author and researcher at the Center for Astrophysics | Harvard & Smithsonian. "Polarization is one of the most direct probes into the magnetic field that nature provides."

The EHT collaboration has been studying the supermassive object at the heart of M87 for well over a decade. In April 2019, the team's hard work paid off when they revealed the very first image of a black hole. Since then, the scientists have delved deeper into the data, discovering that a significant fraction of the light around the M87 black hole is polarized.

Light becomes polarized when it goes through certain filters, like the lenses of polarized sunglasses, or when it is emitted in hot regions of space that are magnetized. In the same way polarized sunglasses help us see better by reducing reflections and glare from bright surfaces, astronomers can sharpen their view of the black hole by looking at how light originating from there is polarized. Specifically, polarization allows astronomers to map the magnetic field lines present around the inner edge of the black hole.

"In order to gain confidence in our analysis, we used as many as five distinct methods to calibrate the data and reconstruct polarimetric images," says Maciek Wielgus, a researcher at Harvard's Black Hole Initiative and the Center for Astrophysics (CfA) who participated in the study. "This huge team effort paid off as we found very good consistency between results obtained with all the different techniques."

These new polarized observations of the M87 black hole are key to explaining how the galaxy is able to launch energetic jets from its core, the EHT team says.

One of M87's most mysterious features is the bright jet of matter and energy that emerges from its core and extends at least 100,000 light years away. Most matter lying close to the edge of a black hole falls in. However, some of the surrounding particles escape moments before capture and are blown far out into space in the form of these jets.

Astronomers don't know how jets larger than the galaxy itself are launched from its core, nor how only certain matter falls into the black hole.

Now, with the new image of the black hole in polarized light, the team has looked directly into the region just outside the black hole where this interplay between inflowing and ejected matter occurs.

The observations provide new information about the structure of the magnetic fields just outside the black hole, revealing that only theoretical models featuring strongly magnetized gas can explain what astronomers are seeing at the event horizon.

"Magnetic fields are theorized to connect black holes to the hot plasma surrounding them," says Daniel Palumbo, a co-author and researcher at the Center for Astrophysics. "Understanding the structure of these fields is the first step in understanding how energy can be extracted from spinning black holes to produce powerful jets."

To observe the heart of the M87 galaxy, the EHT collaboration linked eight telescopes around the world, including the Smithsonian Astrophysical Observatory's Submillimeter Array, to create a virtual Earth-sized telescope. The impressive resolution obtained with the EHT is equivalent to that needed to image a credit card on the surface of the Moon.

This unprecedented resolving power allowed the team to directly observe the black hole with polarized light, revealing the presence of a structured magnetic field near the event horizon.

"This first polarized image of the black hole in M87 is just the beginning," says Dominic Pesce, CfA researcher and study co-author. "As the EHT continues to grow, future observations will refine the picture and allow us to study how the magnetic field structure changes with time."

Sheperd Doeleman, founding director of the EHT, added, "Even now we are designing a next-generation EHT that will allow us to make the first black hole movies. Stay tuned for true black hole cinema."

The EHT collaboration involves more than 300 researchers from across the globe and includes 30 scientists and engineers at the Center for Astrophysics | Harvard & Smithsonian.

About the Center for Astrophysics | Harvard & Smithsonian

The Center for Astrophysics | Harvard & Smithsonian is a collaboration between Harvard and the Smithsonian designed to ask--and ultimately answer--humanity's greatest unresolved questions about the nature of the universe. The Center for Astrophysics is headquartered in Cambridge, MA, with research facilities across the U.S. and around the world.

About the Event Horizon Telescope (EHT) Collaboration

The EHT collaboration involves more than 300 researchers from Africa, Asia, Europe, North and South America. The international collaboration is working to capture the most detailed black hole images ever obtained by creating a virtual Earth-sized telescope. Supported by considerable international investment, the EHT links existing telescopes using novel systems -- creating a fundamentally new instrument with the highest angular resolving power that has yet been achieved.

The individual telescopes involved are: ALMA, APEX, the IRAM 30-meter Telescope, the IRAM NOEMA Observatory, the James Clerk Maxwell Telescope, the Large Millimeter Telescope, the Submillimeter Array, the Submillimeter Telescope, the South Pole Telescope, the Kitt Peak Telescope and the Greenland Telescope.

The EHT consortium consists of 13 stakeholder institutions: the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the Center for Astrophysics | Harvard & Smithsonian, the University of Chicago, the East Asian Observatory, Goethe-Universitaet Frankfurt, Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, Max Planck Institute for Radio Astronomy, MIT Haystack Observatory, National Astronomical Observatory of Japan, Perimeter Institute for Theoretical Physics and Radboud University.

## How to video a black hole

The next big aim for the project is to use the expanded array to allow the scientists to capture the first movies of black holes. When it comes to viewing the way that a black hole changes over time, the enormous size of M87 gives an advantage in allowing scientists to capture it in images or video.

“For M87, which is a monster, it’s six and a half billion times the mass of our sun,” Doeleman said. “The time it takes to orbit around the black hole at the closest orbit that matter can move around is on the order of days, or more likely a month or so.

“So if you wanted to see the black hole evolve before your eyes, you would do it with time-lapse photography. You take an image one week, and then a week later, and then a week later, and if you did that over a few months, you would have a movie you could playback which would show you how the black hole is changing its shape, how the plasma around the black hole is being shocked and dragged around, how jets are being launched from the north and south pole.”

An artist’s conception of a black hole generating a jet. NASA / Dana Berry / SkyWorks Digital

When it comes to the black hole in the center of the Milky Way, however, observing it over time is much more difficult due to its comparatively small size. “Sagittarius A* is a completely different animal,” Doeleman explained. “It’s four million solar masses, so it evolves so quickly that objects orbit around it in half an hour. Trying to capture an image of that is unfortunately like opening up your lens cap and exposing your film while a runner sprints by. It’ll be very blurry.

“But if we can take snapshots, then we’ll be able to stitch those together to make a movie. And for that, we have people developing new algorithms. Instead of combining all the data from one night, they look at snapshots and then make sure they are fluid and continuous as we construct a movie.”

By using complex algorithms, the scientists are able to squeeze more useable information out of the data that they collect, leading to both more sharp and accurate images and to the possibility of new formats such as movies.

## Unexpectedly Large Black Holes and Dark Matter

The M87 black hole blasts relativistic plumes of gas 5000 ly from the centre of the galaxy (NASA)

I just spent 5 minutes trying to think up a title to this post. I knew what I wanted to say, but the subject is so “out there” I’m not sure if any title would be adequate. As it turns out, the title doesn’t really matter, so I opted for something more descriptive…

So what’s this about? Astronomers think they will be able to “see” a supermassive black hole in a galaxy 55 million light years away? Surely that isn’t possible. Actually, it might be.

When Very Long Baseline Interferometry is King

Back in June, I reported that radio astronomers may be able to use a future network of radio antennae as part of a very long baseline interferometry (VLBI) campaign. With enough observatories, we may be able to resolve the event horizon of the supermassive black hole lurking at the centre of the Milky Way, some 26,000 light years away from the Solar System.

The most exciting thing is that existing sub-millimeter observations of Sgr. A* (the radio source at the centre of our galaxy where the 4 million solar mass black hole lives) suggest there is some kind of active structure surrounding the black hole’s event horizon. If this is the case, a modest 7-antennae VLBI could observe dynamic flares as matter falls into the event horizon.

It would be a phenomenal scientific achievement to see a flare-up after a star is eaten by Sgr. A*, or to see the rotation of a possibly spinning black hole event horizon.

All of this may be a possibility, and through a combination of Sgr. A*’s mass and relatively close proximity to Earth, our galaxy’s supermassive black hole is predicted to have the largest apparent event horizon in the sky.

M87 Might be a Long Way Away, But…

As it turns out, there could be another challenger to Sgr. A*’s “largest apparent event horizon” crown. Sitting in the centre of the active galaxy called M87, 55 million light years away (that’s over 2,000 times further away than Sgr. A*), is a black hole behemoth.

M87’s supermassive black hole consumes vast amounts of matter, spewing jets of gas 5,000 light years from the core of the giant elliptical galaxy. And until now, astronomers have underestimated the size of this monster.

Karl Gebhardt (Univ. of Texas at Austin) and Thomas Jens (Max Planck Institute for Extraterrestrial Physics in Garching, Germany) took another look at M87 and weighed the galaxy by sifting through observational data with a supercomputer model. This new model accounted for the theorized halo of invisible dark matter surrounding M87. This analysis yielded a shocking result the central supermassive black hole should have a mass of 6.4 billion Suns, double the mass of previous estimates.

Therefore, the M87 black hole is around 1,600 times more massive than our galaxy’s supermassive black hole.

A Measure for Dark Matter?

Now that the M87 black hole is much bigger than previously thought, there’s the tantalizing possibility of using the proposed VLBI to image M87’s black hole as well as Sgr. A*, as they should both have comparable event horizon dimensions when viewed from Earth.

Another possibility also comes to mind. Once an international VLBI is tested and proven to be an “event horizon telescope,” if we are able to measure the size of the M87 black hole, and its mass is confirmed to be in agreement with the Gebhardt-Jens model, perhaps we’ll have one of the first indirect methods to measure the mass of dark matter surrounding a galaxy…

Oh yes, this should be good.

UPDATE! How amiss of me, I forgot to include the best black hole tune ever:

Publication: The Black Hole Mass, Stellar Mass-to-Light Ratio, and Dark Matter Halo in M87, Karl Gebhardt et al 2009 ApJ 700 1690-1701, doi: 10.1088/0004-637X/700/2/1690.
Via: New Scientist

## New technology is a 'science multiplier' for astronomy

The first image of a black hole by the the Event Horizon Telescope in 2019 was enabled in part b support for the NSF's Advanced Technologies and Instrumentation program. Credit: NASA

Federal funding of new technology is crucial for astronomy, according to results of a study released Sept. 21 in the Journal of Astronomical Telescopes, Instruments and Systems.

The study tracked the long-term impact of early seed funding obtained from the National Science Foundation. Many of the key advances in astronomy over the past three decades benefited directly or indirectly from this early seed funding.

Over the past 30 years, the NSF Advanced Technologies and Instrumentation program has supported astronomers to develop new ways to study the universe. Such devices may include cameras or other instruments as well as innovations in telescope design. The study traced the origins of some workhorse technologies in use today back to their humble origins years or even decades ago in early grants from NSF. The study also explored the impact of technologies that are just now advancing the state-of-the-art.

The impact of technology and instrumentation research unfolds over the long term. "New technology is a science multiplier" said study author Peter Kurczynski, who served as a Program Director at the National Science Foundation and is now the Chief Scientist of Cosmic Origins at NASA Goddard Space Flight Center. "It enables new ways of observing the universe that were never before possible." As a result, astronomers are able to make better observations, and gain deeper insights, into the mysteries of the cosmos.

The study also looked at the impact of grant supported research in the peer-reviewed literature. Papers resulting from technology and instrumentation grants are cited with the same frequency as those resulting from pure science grants, according to the study. Instrumentation scientists "write papers to the same degree, and with the same impact as their peers who do not build instruments," said Staša Milojevi, associate professor of informatics and the director of the Center for Complex Network and Systems Research in the Luddy School of Informatics, Computing and Engineering at Indiana University, who is a coauthor of the study.

Also noteworthy is that NSF grant supported research was cited more frequently overall than the general astronomy literature. NSF is considered to have set the gold standard in merit review process for selecting promising research for funding.

An anonymous reviewer described the article as a "go-to record for anyone needing to know the basic history of many breakthroughs in astronomical technology." Better observations have always improved our understanding of the universe. From the birth of modern astronomy in the middle ages to the present day, astronomers have relied upon new technologies to reveal the subtle details of the night sky with increasing sophistication.

## One Step Closer to Black Hole’s Event Horizon

An international team of astrophysicists has the first time measured the black hole’s ‘point of no return’ – the closest distance that matter can approach before being irretrievably pulled into the black hole.

This artist’s conception shows the region immediately surrounding a supermassive black hole. The black hole is orbited by a thick disk of hot gas. The center of the disk glows white-hot, while the edge of the disk is shown in dark silhouette. Magnetic fields channel some material into a jet-like outflow – the greenish wisps that extend to upper right and lower left. A dotted line marks the innermost stable circular orbit, which is the closest distance that material can orbit before becoming unstable and plunging into the black hole (Chris Fach / Perimeter Institute & University of Waterloo)

“Once objects fall through the event horizon, they’re lost forever,” said Dr Sheperd Doeleman, assistant director at the MIT Haystack Observatory and research associate at the Harvard-Smithsonian Center for Astrophysics, who led the study published in the Science Express. “It’s an exit door from our Universe. You walk through that door, you’re not coming back.”

The team examined the supermassive black hole at the center of a giant elliptical galaxy called Messier 87, which is located about 50 million light-years from Earth. That black hole is 6 billion times more massive than the Sun. It’s surrounded by an accretion disk of gas swirling toward the black hole’s maw. Although the black hole is invisible, the accretion disk is hot enough to glow.

“Even though this black hole is far away, it’s so big that its apparent size on the sky is about the same as the black hole at the center of the Milky Way,” said co-author Dr Jonathan Weintroub of the Harvard-Smithsonian Center for Astrophysics. “That makes it an ideal target for study.”

According to Einstein’s theory of general relativity, a black hole’s mass and spin determine how close material can orbit before becoming unstable and falling in toward the event horizon. The team was able to measure this innermost stable orbit and found that it’s only 5.5 times the size of the black hole’s event horizon. This size suggests that the accretion disk is spinning in the same direction as the black hole.

The observations were made by linking together radio telescopes in Hawaii, Arizona and California to create a virtual telescope called the Event Horizon Telescope. The telescope is capable of seeing details 2,000 times finer than the Hubble Space Telescope.

The team plans to expand its telescope array, adding radio dishes in Chile, Europe, Mexico, Greenland, and the South Pole, in order to obtain even more detailed pictures of black holes in the future.

Bibliographic information: Sheperd S. Doeleman et al. Jet-Launching Structure Resolved Near the Supermassive Black Hole in M87. Science, published online September 27 2012 doi: 10.1126/science.1224768

## Astronomers Measure a Black Hole&rsquos &ldquoPoint of No Return&rdquo

This artist&rsquos conception shows the region immediately surrounding a supermassive black hole (the black spot near the center). The black hole is orbited by a thick disk of hot gas. The center of the disk glows white-hot, while the edge of the disk is shown in dark silhouette. Magnetic fields channel some material into a jet-like outflow &ndash the greenish wisps that extend to upper right and lower left. A dotted line marks the innermost stable circular orbit, which is the closest distance that material can orbit before becoming unstable and plunging into the black hole. Credit: Chris Fach (Perimeter Institute & University of Waterloo)

For the first time, international team of astronomers has measured a black hole&rsquos &ldquopoint of no return,&rdquo the closest distance that matter can approach before being irretrievably pulled into the black hole.

Using a continent-spanning telescope, an international team of astronomers has peered to the edge of a black hole at the center of a distant galaxy. For the first time, they have measured the black hole&rsquos &ldquopoint of no return&rdquo &mdash the closest distance that matter can approach before being irretrievably pulled into the black hole.

A black hole is a region in space where the pull of gravity is so strong that nothing, not even light, can escape. Its boundary is known as the event horizon.

&ldquoOnce objects fall through the event horizon, they&rsquore lost forever,&rdquo says lead author Shep Doeleman, assistant director at the MIT Haystack Observatory and research associate at the Harvard-Smithsonian Center for Astrophysics (CfA). &ldquoIt&rsquos an exit door from our universe. You walk through that door, you&rsquore not coming back.&rdquo

The team examined the black hole at the center of a giant elliptical galaxy called Messier 87 (M87), which is located about 50 million light-years from Earth. The black hole is 6 billion times more massive than the sun. It&rsquos surrounded by an accretion disk of gas swirling toward the black hole&rsquos maw. Although the black hole is invisible, the accretion disk is hot enough to glow.

&ldquoEven though this black hole is far away, it&rsquos so big that its apparent size on the sky is about the same as the black hole at the center of the Milky Way,&rdquo says co-author Jonathan Weintroub of the CfA. &ldquoThat makes it an ideal target for study.&rdquo

According to Einstein&rsquos theory of general relativity, a black hole&rsquos mass and spin determine how close material can orbit before becoming unstable and falling in toward the event horizon. The team was able to measure this innermost stable orbit and found that it&rsquos only 5.5 times the size of the black hole&rsquos event horizon. This size suggests that the accretion disk is spinning in the same direction as the black hole.

Streaming out from the center of the galaxy M87 like a cosmic searchlight is one of nature&rsquos most amazing phenomena, a black-hole-powered jet of sub-atomic particles traveling at nearly the speed of light. In this Hubble Space Telescope image, the blue of the jet contrasts with the yellow glow from the combined light of billions of unseen stars and the yellow, point-like globular clusters that make up this galaxy. Credit: NASA and the Hubble Heritage Team

The observations were made by linking together radio telescopes in Hawaii, Arizona, and California to create a virtual telescope called the Event Horizon Telescope, or EHT. The EHT is capable of seeing details 2,000 times finer than the Hubble Space Telescope.

The team plans to expand its telescope array, adding radio dishes in Chile, Europe, Mexico, Greenland, and the South Pole, in order to obtain even more detailed pictures of black holes in the future.

## New Greenland telescope is up and running

The large telescope in Greenland, near Thule airbase. Credit: CfA

Greenland can now brag about hosting a large, operational radio telescope, with a dish measuring 12 metres in diameter.

The Greenland Telescope was installed in 2017 and it is now a part of a global network of telescopes, including the large ALMA observatory (Atacama Large Millimeter/submillimeter Array) in Chile.

It is located on the northwest coast at the US Thule airbase, and is part of an ambitious project, the Event Horizon Telescope (EHT), to study black holes.

Black holes are areas of space where the concentration of matter is so high that gravity is incredibly strong. So strong, in fact, that no light can escape when it ventures too close.

Galaxy M87 contains a gigantic black hole

The EHT project will generate images of two large black holes: One in the middle of our own galaxy, the Milky Way, and another, bigger black hole, in the centre of nearby galaxy M87.

Other telescopes in Chile and Hawaii will point in the same direction, and data will be pooled from all of the telescopes in the EHT project to produce the images.

"The EHT essentially turns the entire globe into one giant radio telescope, and the farther apart radio dishes in the array are, the sharper the images the EHT can make," says EHT project leader, Sheperd Doeleman from the Harvard-Smithsonian Center for Astrophysics, USA.

"The Greenland Telescope will help us obtain the best possible image of a supermassive black hole outside our galaxy," he says.

In fact, without the Greenland Telescope, astronomers would not be able to image the M87 galaxy black hole.

Telescope sees the shadow of a black hole

Black holes are not easy to observe, as they do not shine. Instead, astronomers try to catch a glimpse of the shadow they cast, says Marianne Vestergaard, associate professor at the Niels Bohr Institute at the University of Copenhagen, Denmark.

"We hope to see the shadow of the black hole. There will be a glow of light from gas and plasma around the black hole from material that is about to be engulfed. But since the black hole does not shine, its silhouette will appear dark surrounded by light," she says.

Data from telescopes in Chile, Hawaii, and Greenland, will be combined to produce an image of a black hole. Credit: ASIAA

Such an image would be excellent evidence for the existence of black holes, should anyone still be in doubt, which is unlikely after the gravitational waves caused by two merging black holes were detected in 2016.

Scientists also want to study the jets of material ejected from the holes—the so-called radio-jets, says Vestergaard. For example, they would like to know how and where the jets are formed in relation to the black hole. Vestergaard studies black holes, but is not directly involved with the ETH project.

The first image of a black hole is on the way

The Greenland Telescope is now fully operational and collecting data, but there are plans to move it further inland, away from the relatively moist air on the coast, and up high on to the summit of the ice sheet where the air is drier.

"Moving the telescope up to the ice sheet where it can be of most use, is absolutely desirable," says Vestergaard.

Greenlandic students visit the telescope, which will also be used for teaching. Credit: CfA

"On top of the ice sheet, you are about three kilometres above sea level. The shorter distance the signal has to go through the atmosphere, the less it is absorbed," she says.

The project has several years to run in order to collect enough data to create sharp images. But astronomers are already beginning to analyse the preliminary data, and it could be just a few months before they produce the first, albeit fuzzy, images of a black hole.

This story is republished courtesy of ScienceNordic, the trusted source for English-language science news from the Nordic countries. Read the original story here.