Astronomy

When we say the sun takes 230M years to orbit the galaxy, what is this in relation to?

When we say the sun takes 230M years to orbit the galaxy, what is this in relation to?

When we say the sun takes 230M years to orbit the galaxy, what is this in relation to? We measure the earth's rotation relative to the distant stars. What is the reference for our Sun's motion around the galaxy?


The Sun's velocity is known (with uncertainties) with respect to the Galactic centre (GC), as is the Sun's distance from the Galactic centre. These measurements have a long tortuous history, which I am not going to attempt to summarise here. However, the motion of the Sun with respect to the GC is established by measuring the proper motion of the Sgr A* source with respect to the assumed zero proper motions of distant radio quasars (see for example Backer & Sramek 1999; Reid & Brundthaler 2004).

The astrometry frame of reference now is known as the International Celestial Reference Frame and is defined by hundreds of compact, extragalactic radio sources.

If you then assume the Sun's orbit is circular and that Sgr A* is at the GC, then the job is done - the relative velocity divided by the distance to the GC gives the angular velocity $Omega$, and the orbital period is $2pi/Omega$ . If you have a model for the Galactic potential then you can do a bit better.


When we say the sun takes 230M years to orbit the galaxy, what is this in relation to? - Astronomy

I would like to know if there is anything or any lonely galaxies between Clusters.

Yes there are galaxies that are not associated with clusters of galaxies. In the past it was thought that galaxies in groups or cluster were only a small fraction of the total number of galaxies, but now large galaxy surveys show that the situation is quite different. For example check out this image. It shows the distribution of 100,000 nearby galaxies. You can probably see that there is a lot of structure there: large groups of galaxies, filaments, and voids. This tells you that most galaxies are part of groups or clusters, or you wouldn't see such structure in the distribution of galaxies.

But there exists quite a variety of environments where galaxies can be found: from very dense clusters, to less dense clusters, small groups, and very low density regions of space. These last galaxies are what we call 'field galaxies'. They are basically galaxies that are not in gravitational systems with other galaxies. So even though there is a lot of structure in the Universe, we can still find galaxies that are not part of groups or clusters. There is some interest in these galaxies, in studying the different properties they have with respect to galaxies in clusters. These are the "lonely galaxies" that are between clusters of galaxies, as you say.

This page was last updated on January 28, 2019

About the Author

Amelie Saintonge

Amelie is working on ways to detect the signals of galaxies from radio maps.


Something in Space Warped the Dang Milky Way

Astronomers and physicists have been trying to understand why this weird wobble exists for decades. Now, physicists believe they've solved this strange, celestial mystery.

The international team of scientists analyzed data collected by the European Space Agency's Gaia telescope, which created a map of the Milky Way in 2018, charting the position of almost 1.7 billion stars in our galaxy. Specifically, the team studied the speed at which more than 12 million stars within the warped part of the Milky Way orbit the center of our galaxy.

&ldquoWe measured the speed of the warp by comparing the data with our models,&rdquo said team leader Eloisa Poggio, of the Turin Astrophysical Observatory, in a statement. &ldquoBased on the obtained velocity, the warp would complete one rotation around the centre of the Milky Way in 600 to 700 million years.&rdquo They published the results of their work March 2 in the journal Nature Astronomy.

By comparison, other stars in non-warped regions of the Milky Way take a much shorter route around our galaxy's center. The sun, for example, takes approximately 230 million years to orbit the Milky Way.

Why the delay? Poggio and her team believe it's a case of close encounters of the galactic kind. Their simulations show a gargantuan intergalactic collision occurred recently and may still be happening. So, which of our galactic neighbors could be responsible for throwing the Milky Way off kilter?

The likely culprit of this cosmic conundrum is the dwarf galaxy Sagittarius, which circles the Milky Way along an orbit about 65,230 light-years away from Earth. The tiny galaxy is approximately 10,000 light-years across compared to the Milky Way's 100,000-light-year span.


Pronunciation 101

Another benefit of having experienced astronomers along for your night under the stars is that they can tell you how to pronounce the names of constellations and starsthat might be unfamiliar to you — or how to correctly say the name of our solar system's seventh planet. I always chuckle when a youngster (usually of the male gender) tries to trick me into saying Uranus. They are always disappointed when I say "Yoor-a-nus," and not "Your-ay-nus."

Most of the names for classical constellations are Latin words or phrases, while the proper names for stars are usually derived from Arabic. While many names are single syllables, quite a few are a mouthful. Fortunately, the Cosmic Collection includes correct pronunciations for 500 stars, constellations, deep-sky objects and planets. [Name That Star! Ancient Cultures Lend Titles to 86 Suns]

For example, the northerly constellation of Monoceros translates to Unicorn. When pronounced correctly, it sounds like rhinoceros. Another tongue-twisting constellation is Camelopardalis. The name comes from the Greek roots: kamēlos ("camel") and pardalis ("leopard"). The combined word means giraffe, although the constellation is actually a camel — the one that Rebecca and Isaac rode in a Bible story. The app tells us to pronounce it "Ca-mel-o-pard-a-lis".

The naked-eye star sitting just below Jupiter this summer is named Zubenelgenubi, derived from the Arabic phrase "al-zuban al-janubiyy," which means "southern claw." (It used to be part of the constellation Scorpius.) Once you learn to pronounce it properly, it rolls right off the tongue!

To hear the pronunciation for an object, select it, then tap the Selection icon, and then tap the bubble-shaped pronunciation icon. You can also use the pronunciation icon displayed at the upper right corner of the object's Info page. As with the Audio Tours, the icon will be grayed-out if no pronunciation is available. Alternate pronunciations are provided, too.


Is this the Kali yuga or the Dwapara yuga?

Sadhguru explains the science behind the cycle of four yugas with precise calculations and states that we are deep into the Dwapara yuga now.

What are yugas?

In the yogic astronomy, we divide the orbit of the Earth around the Sun into 27 segments, called nakshatras or stars. Each nakshatra is further divided into four equal sectors called padas or steps. Multiply 4 by 27 and it equals 108. These 108 units mark the 108 steps that the Earth takes through space. Each nakshatra corresponds to one half of the lunar orbit around the Earth. Likewise, the cycles within the human body also respond and correspond to the planetary cycle.

In a woman&rsquos body, there are very obvious cycles of 27.55 days if she is perfectly healthy. In a man&rsquos body, the cycles are less obvious and pronounced &ndash they happen in a different way and are of a larger span of time. These cycles are happening continually in the solar system and in the larger universe. The microcosm and the macrocosm both are playing the same game.

But then you could ask the question, who should play whose game? If you think the macrocosm is going to play your game, you are mistaken and you will be simply wasting your life. But instead, if you play the macrocosm&rsquos game, your life will be beyond your expectations.

The precession (caused by gradual rotation of the Earth&rsquos axis) of the equinoxes is the period of time that it takes the Earth&rsquos axis to pass through one complete cycle of the zodiac. It takes the planet 72 years to pass through one degree of the zodiac and 25,920 years to complete one full circle of 360 degrees. One half of the journey, either the descending or the ascending journey takes 12,960 years and in that time, each half will cover all the four yugas. Kali Yuga lasts 1296 years, Dwapara Yuga lasts 2592 years, double as many years as the Kali yuga, Treta Yuga lasts 3888 years, three times that of the Kali yuga and Satya Yuga lasts 5184 years, 4 times that of the Kaliyuga. These four yugas put together come to a total of 12,960 years. The two Kali yugas reach us one after the other because they appear at the bottom of the ellipse and hence we could say that Kaliyuga stretches for a period of 2592 yrs. Likewise, the two Satya yugas reach us one after the other because they appear at the top of the ellipse and hence the Satya yuga stretches for a period of 12,960 yrs.

We are in the Dwapara Yuga

The story of Mahabharat needs to be seen in a certain context. In 3140 BCE, the Kurukshetra War ended, and in 3102 BCE, Krishna left his body. Three to four months after the war, the Kali Yuga began. As of 2012 AD, Krishna&rsquos era ended 5,114 years ago. If you subtract 2592, which is the cumulative number of years of the two Kali Yugas that are at the bottom of the ellipse which describes the axial precession, you arrive at 2522 years. That means, we have already completed 2522 years of Dwapara Yuga, and since its total duration is 2592 years, we still have 70 years until its completion. In the year 2082, we will complete Dwapara Yuga and move on to Treta Yuga.

The world will go through another upheaval, not necessarily in terms of war but probably in terms of population explosion and natural calamities before moving on to this new era of wellbeing and upward movement of human consciousness.

How does the yugas affect Human Consciousness?

The solar system with the Sun and the planets around it is moving in the galaxy at a steady pace. It takes 25,920 years for our solar system to complete one cycle around a larger star. From the effects that are noticeable upon the planet, we assume that this super star, around which our system is revolving, is not located in the centre of the orbit, but somewhere to the side. Whenever our solar system gets closer to this super star, all the creatures belonging to this system rise to greater possibilities and whenever our system moves away from it, the creatures descend to theri lowest level of possibility &ndash and that period. we refer to as the Kali Yuga.

When our solar system is closest to the &ldquoSuper Sun,&rdquo what we refer to as the Satya Yuga begins. The human mind will be at its highest potential during that period, which is quite long - 12,960 yrs. One&rsquos ability to be acquainted with life, one&rsquos ability to communicate, one&rsquos ability to live joyfully, everything will be at its peak. Without any external prompting, people will turn wiser and more competent.

For peace and contentment to prevail on this earth, what else do we need, other than human beings who are sensible and joyful?

The ether level and spirituality

In Satya Yuga, human ability to communicate will be at its peak because the etheric sphere will be very close to the planet. When the ether level is very high, if I want to convey something to you, I do not even have to say it. Even if my eyes are closed, it will get across to you. When the ether level is a little high, I may not be able to communicate to you with my eyes shut, but if I open my eyes and look at you, you will know what I wish to convey.

The ether level in dense forests will be high because of such concentrated life energy. Your vision is blocked to some extent, but after some time, you realise that you are able to recognise things by their smell. You do not have to apply your sense of sight much. Most animals that live there differentiate things by their smell and they tend to make use of their sense of hearing more. In fact, if you talk much, the beings that live in the forests get confused.

On the other hand, when the ether level is very low, you have to keep talking, repeating things again and again &ndash otherwise, people will not get the hang of it. Even when you talk, they find it difficult to understand the profundity of what you are speaking about. The ether content in the atmosphere determines how sensitive you will be in terms of your ability to communicate.

At the same time, no matter which time, which yuga, which planetary position you are in right now, every individual human being has the capacity to rise above all this. Even in the worst of times that possibility for one to sustain the golden era within oneself remains unhindered.

It is possible to enhance the ether level or create an etheric atmosphere. Krishna has said, &ldquoDuring Kali Yuga, which is way down there in the Yuga cycle, far away from the Super Sun, the ether will be so low that there is no point in trying to teach people yoga, meditation, mantras or yantras &ndash they will not be able to grasp it. Just teach them devotion. If they are devout, they will be able to generate their own ether. Even if one doesn&rsquot have the dexterity to grasp anything much, with the aid of immaculate devotion, one can reach one&rsquos goal.&rdquo

Thousands of years ago, our sages and seers had foreseen that as the solar system moves closer to the Super Sun, human intelligence will blossom to its core. The reality is that, as the solar system moves closer, as the ether level increases, the realization that your own body and the whole universe are of the same electric structures, that they are in effect - one and the same - will occur to you naturally.

Right now, we are moving towards Treta Yuga, which is the second greatest period that can happen in a cycle of yugas. It has been stated by Krishna again that after a break of 5000 years, a time will reach us which will be the golden age and that the glorious period will last for several thousands of years. We, the people who are living on this planet now will not make it there, but we can set the foundations for the coming generations and reel in the joy for having taken an active part in creating the necessary atmosphere that would facilitate the planet to prepare itself for those thousands of years of splendour.

This is not just predictions and conjectures &ndash this is based on a deep-rooted understanding about what happens with the human mind in relation to the planetary system on which we live.

We not only live on this planet &ndash we are the planet!

If you do not understand this today, you will understand this when you are buried. The planet understands that you are a part of it &ndash only you think different!

The above said account fits relatively close with the modern astronomical calculation of one full precession of the equinox, which takes 25,772 years.

According to the Laws of Manu, one of the earliest known texts describing the yugas, the lengths are approximately 4800 years + 3600 years + 2400 years + 1200 years, for a total of 12,000 years for one arc, or 24,000 years to complete the cycle, which is approximately one precession of the equinox. These 4 yugas follow a timeline ratio of (4:3:2:1).

If we follow the chart of the saptarishis, that also indicates the same as mentioned in the article with a 300 yr transitional period in between every yuga.

Swami Sri Yukteswar, Yogananda's guru, among others, have disputed about what is said in the Srimad Bhagavatam saying that it is a miscalculation by the people who deciphered it and said that we are living in "Dwapara Yuga" as per the Vedas.


X-ray data reveal 1st-ever planet orbiting stars in another galaxy

The Whirlpool Galaxy (M51), where the candidate exoplanet M51-ULS-1b was detected by the Chandra X-ray Observatory. We see this galaxy face-on. Image via NASA/ ESA/ S. Beckwith (STScI)/ the Hubble Heritage Team (STScI/AURA).

In recent decades, astronomers have found over 4,000 exoplanets, or worlds orbiting other stars. They range from small, rocky planets to huge gas giants, but they all have one thing in common. Every exoplanet found orbiting a star has so far resided in our own Milky Way galaxy. That makes sense, since the Milky Way’s own stars are the stars closest to us, cosmically-speaking. But now scientists at the Harvard-Smithsonian Center for Astrophysics – led by Rosanne Di Stefano – have used X-ray data to take the giant step across extragalactic space, to find the first evidence for a planet orbiting stars in another galaxy.

The planet, still a candidate at this point, appears to orbit a binary star system – two stars in a mutual orbit – in the glorious Whirlpool Galaxy (M51), a galaxy we see face-on, at a staggering 23 million light-years from Earth.

The extragalactic news was reported in The Physics arXiv Blog by Astronomy.com on September 24, 2020.

A new peer-reviewed paper detailing the discovery was submitted to arXiv on September 18, 2020.

Image of the Whirlpool Galaxy from Chandra. The M51-ULS-1 star system, seen in bright X-rays, is the orange dot in the center of the square. Image via R. Di Stefano et al./ MNRAS.

The planet has been labeled M51-ULS-1b, and is estimated to be slightly smaller than Saturn. It orbits its stars about 10 times the distance from Earth to the sun. It was first detected on September 20, 2012, by NASA’s Chandra X-ray Observatory, but went unnoticed in the datasets at the time. It was only later found by Di Stefano and other colleagues.

It’s an exciting finding, but how did astronomers do it, especially when it can be difficult enough just to find planets in our own galaxy?

The answer is that this binary star system is rather unique. One of the two stars in the binary is simply a massive star. But the other one is thought to be a stellar remnant, either a neutron star or a black hole. The massive star is gradually being consumed by the neutron star or black hole companion, either of which would have extreme gravitational pull. The resulting dust releases huge amounts of energy in the form of X-rays, the same electromagnetic radiation used to take images of the inside of a human body or other objects. The amount of X-rays being released is so massive that this binary system is one of the brightest sources of X-rays in the entire Whirlpool Galaxy.

Also, whether the object emitting the X-rays is a neutron star or black hole, it is very small, smaller than a lot of planets. The team calculated that if a Saturn-sized planet orbited it, and transited in front of it from our vantage point – the way many exoplanets are discovered – it would entirely eclipse the object. As seen by Chandra, the transit lasted about three hours.

The extragalactic planet was first detected by the Chandra X-ray Observatory in 2012, but not noticed until much later (artist’s illustration). Image via NASA/ Chandra X-ray Observatory.

Couldn’t the possible planet actually be another star? The researchers say no, since the binary system is too young for other white dwarfs or other stars to have evolved there. What about natural variations in brightness of the neutron star or black hole? Again, the team says this is unlikely, because the different light frequencies in the spectrum all dimmed and then brightened again at the same time, exactly what would be expected of an eclipse by a larger body passing in front:

It is approximately symmetric, and has a shape typical of transits in which the source and transiting object have comparable size.

The researchers now expect that additional planetary candidates will be found soon:

The archives contain enough data to conduct surveys comparable to ours more than ten times over. We therefore anticipate the discovery of more than a dozen additional extragalactic candidate planets in wide orbits.

Since our own galaxy alone is now estimated to contain billions of planets, maybe even more planets than stars, it is reasonable to conclude that other galaxies do as well.

This discovery is tantalizing, but it is not actually the first possible detection of a planet in another galaxy. As reported in EarthSky in February 2018, astronomers at the University of Oklahoma (UO) announced evidence for multiple planets in a galaxy 3.8 billion light-years away, which contains the quasar RX J1131-1231. The main difference with these is that they are free-floating “rogue” planets not orbiting any stars, and the evidence for them is less direct, using a quasar microlensing technique where the gravity from the quasar acts as a natural magnifying glass. The quasar magnifies the light coming from its galaxy, making it easier to detect distant features.

Rosanne Di Stefano at the Harvard Smithsonian Center for Astrophysics, who led the discovery team. Image via Harvard University.

That discovery was also made using Chandra. Using microlensing models at OU’s supercomputing center, the researchers calculated there could be as many as 2,000 rogue exoplanets in that galaxy, ranging from the mass of the moon to the mass of Jupiter.

Millions or more rogue planets like these are also now thought to exist in our own galaxy, but whether they were ejected from their original planetary systems or just formed where they are isn’t known yet.

M51-ULS-1b, however, would be the first “regular” planet discovered in a nearby galaxy, one that orbits a star. That bodes well for the prospect of many more being found in the years ahead. If our galaxy, the Whirlpool Galaxy and others are filled with planets, then how many worlds might there be in the universe? It’s a mind-bending thought, especially when it was first believed there were about 200 billion galaxies in the observable universe, but more recent studies say there are at least 10 times that many, or 2 trillion galaxies. Wow.

Bottom line: Astronomers used X-ray data to make the first discovery of an an exoplanet – labeled M51-ULS-1b – orbiting a star in another galaxy. The planet appears to orbit in a double-star system in the Whirlpool galaxy (M51), 23 million light-years away.


SIRIUS, the GREATer CENTRAL SUN and Alcyone, the Central Sun - Galactic Alignment in 2012

ATTENTION: According to my latest research - 3 January 2013 - Our solar system does not orbit Alcyone but SIRIUS - which in turn revolves around Alcyone - and we all are rotating around the Galactic Centre - or Hunab Ku.

Thus, the following information below must be revised . and Nibiru? Well, we find many speculations - but none confirm the point of view given here in this message.

Our Earth along with other planets revolve around the Sun . The Sun, along with 6 other stars, in turn revolve around a bigger star, Alcyone [in the Pleiades star system], also known as the Central Sun. Alcyone revolves around a much bigger star, Sirius, which is called as the Greater Central Sun. This system of stars revolving around one another, is a feature found in all galaxies in our Universe where ultimately, each galaxy consisting of stars and planets, revolves around its own centre. The Milky way galaxy, to which our Earth belongs, has billions of such stars and planets, all revolving around a massive star in its core, called as the Galactic Centre.

Galactic Alignment in 2012

As the Sun and other stars revolve around one another and move in their orbits, they come in various alignments with each other. On 21st December 2012, two alignments are expected to occur in our Milky Way Galaxy. One, our Sun and the entire solar system will come in direct alignment with the Galactic equator. And two, the Galactic Centre, the Greater Central Sun and the Central Sun will form an equilateral triangle in space at the same time.

Our Earth receives energies, both physical and subtle from the Sun as well as other stars. To receive the maximum amount of Energies, it has to come in a proper alignment with these celestial bodies. For example, during an eclipse, where the Earth, Sun and Moon align with each other, very rare spiritual energies flood our Earth because of this alignment. Hence the duration of eclipses were considered sacred and were spent in meditations and other spiritual activities, to make the best use of these subtle energies.

An alignment occurring at the level of the Galactic Centre will have an effect which is many, many times higher in magnitude. When our Earth, along with the solar system aligns with the Galactic equator, it will come in direct focus of a huge amount of subtle energies, which emerge from the Galactic Centre. And the triangular formation of Alcyone, Sirius and the Galactic centre in 2012 brings a massive amount of spiritual energies from these Stars to our Earth. This rare celestial occurrence has also initiated many other events.

When the Sun moves around the Central Sun, it passes through various energy fields in space. One such energy field is the Photon belt, which is a spiritual field, which came out of the Greater central Sun, Sirius. The Photon belt is a field of very high vibratory frequency, which enhances the spiritual condition of our Earth when we enter it. If we’re spiritually evolved at that time, our evolution will be magnified by many folds. And if our spiritual growth is negative, we go into a very fast downward spiral, as it happened during our last entry, nearly 11,000 years ago, when the great civilization of Atlantis was destroyed.

Our Solar system has begun its entry into this field. Our earth is under the direct influence of the Photon Belt from Dec 21st, 2009 and the effects will increase in seven stages. We are now in the third stage of this influence. This entry of our Earth into the Photon Belt, which coincides with the Galactic alignment happening on the same day, will have a massive spiritual effect on Humanity.

Completion of Grand Cycles

Our Sun takes nearly 26,000 years to complete its orbit around Alcyone. This completion of cycle coincides with the year 2012! And the Central Sun, Alcyone which takes millions of years to revolve around Sirius, also completes its orbit in the same year. At the physical level, this brings about huge changes like the interchanging of the magnetic poles of the Sun, which in turn will trigger similar changes on our Earth. Such a massive change will have a huge bearing on humanity and all life that our Earth houses.

Our Sun has a twin, another star, which is called as the Second Sun. This is also referred to many as Nibiru and Planet X. This star exists at a subtle level and although it usually isn’t visible to the naked eye, it sometimes becomes visible to those who are spiritually evolved and has been photographed.

Since the Second Sun exists at a higher level, it supports life of a higher order, that is, the life in the Golden Age. As we go into the New Crystal Age, we’ll use more of the energies from the Second Sun. These Energies are expected to become more prominent post 2012, because of our entry into the Photon belt and the Galactic Alignment. They help us in our spiritual evolution and in opening up to newer realities.

When important events happen almost simultaneously at the cosmic levels, the effects will also be dramatic and life changing. The events which are scheduled to occur after 2012 are going to release a huge amount of energies, both physical and spiritual, which will have massive effects.


Why does NASA care about years on other planets?

NASA needs to know how other planets orbit the Sun because it helps us travel to those planets! For example, if we want a spacecraft to safely travel to another planet, we have to make sure we know where that planet is in its orbit. And we also have to make sure we don’t run into any other orbiting objects — like planets or asteroids — along the way.

Scientists who study Mars also need to keep a Martian calendar to schedule what rovers and landers will be doing and when.

Mars and Earth are always moving. So, if we want to land a robotic explorer on Mars, we have to understand how Earth and Mars orbit the Sun. Watch this video to learn more about the Martian year. Credit: NASA/JPL-Caltech

*Length of year on other planets calculated from data on the NASA Solar System Dynamics website.


When we say the sun takes 230M years to orbit the galaxy, what is this in relation to? - Astronomy

There were two problems with this relation. First, Kepler did not know how it worked, he just knew it did. Second, the relation does not work for objects which are not orbiting the Sun, for example, the Moon orbiting the Earth. Isaac Newton solved both these problems with his Theory of Gravity, and discovered that the masses of the orbiting bodies also play a part. Newton developed a more general form of what was called Kepler's Third Law that could apply to any two objects orbiting a common center of mass. This is called Newton's Version of Kepler's Third Law:

Special units must be used to make this equation work. If the data are not given in the proper units, they must be converted.

The masses must be measured in solar masses, where one solar mass is 1.99 X 10 33 grams, or 1.99 X 10 30 kilograms.

The semi-major axis must be measured in Astronomical Units, where 1 AU is 149,600,000 kilometers, or 93,000,000 miles.

The orbital period must be measured in years, where 1 year is 365.25 days.

This relation has many uses: determining the mass of a planet by looking at its moon(s), studying binary star systems, even determining the mass of the Galaxy!

There is a problem, however, with the way the equation is written above. Often, we are not able to determine to a high degree of accuracy the average distance between, say, two binary stars. We must use a modified version of NVK3L for very distant objects.

To achieve this modification, we must first introduce an equation for velocity, how fast an object is traveling. Everybody who has driven a car has encountered the formula for velocity. The speedometer on a car measures velocity in miles per hour, or kilometers per hour. Now miles or kilometers are ways of measuring distance, hours are what we use to measure time, and "per" is a word signaling division. Therefore, the formula for velocity is

Velocity = Distance traveled / Time to travel

How does this relate to NVK3L? Remember that our real problem is often that we do not know the average distance between the two objects that are orbiting each other. Many times, we can only clearly see one of the objects that is orbiting! But velocity is something we can measure, as long as we can see one of the partners, using the Doppler Effect.

Technically what we are measuring is the orbital velocity of the visible partner, which can be related to the distance traveled by the visible partner in its orbit and the time it takes the visible partner to orbit once. That time is simply the orbital period P, which is generally easy to observe. What we usually don't know is the distance traveled around the orbit by the visible partner, called the circumference of the orbit. This circumference is related to the average distance, A, by the formula

Circumference = C = 2 (pi) A

So the velocity equation becomes

Velocity = V = C / P = 2 (pi) A / P

Remember that we can compute velocity using the Doppler Effect. We can observe the orbital period easily. It is the value of A that is typically very hard to find. So we turn the equation above around, and solve for A:

We can now take this value of A and plug it in to Newton's Version of Kepler's Third Law to get an equation involving knowable things, like V and P:

M1 + M2 = V 3 P 3 / 2 3 (pi) 3 P 2

What this equation is basically telling us is, the more mass there is in a system, the faster the components of that system are moving as they orbit each other. We shall not use this more complicated version of NVK3L for homework calculations, but we will use the concept in our discussion of black holes.


Where is Earth located in the galaxy?

The Solar System. Credit: NASA

You've probably heard the saying "everything's relative". When you consider our place in the Universe, everything really is relative. I'm recording this halfway up Vancouver Island, in the Pacific Ocean, off the West Coast of Canada. And where I'm standing is about 6,370 kilometers away from the center of the Earth, that way.

From my perspective, the Sun is over there. It's as large as a dime held at arm's length. For me it's really, really far away. In fact, at this exact time it's further away than any object I you can see with the naked eye.I'm about 150 million kilometers away from the Sun, and so are you.

We're carving out an elliptical orbit which takes one full year to complete one whole trip around. You, me and the Earth are all located inside our Solar System. Which contains the Sun, 8 planets and a vast collection of ice, rocks and dust. We're embedded deep within our galaxy, the Milky Way. It's a big flat disk of stars measuring up to 120,000 light years across.

Our Solar System is located in the middle of this galactic disk. And by the middle, I mean the center of the galaxy is about 27,000 light years that way, and the edge of the galaxy is about the same distance that way.

Our Milky Way is but one galaxy in a larger collection of galaxies known as the Local Group. There are 36 known objects in the local group. Which are mostly dwarf galaxies. However, there's also the Triangulum Galaxy, the Milky Way, and the Andromeda galaxy… which is by far the largest, most massive object in the Local Group, It's twice the size and 4 times the mass of the Milky Way.

From me, and you, Andromeda is located just an astronomically distant 2.5 million light years that way. Or would that be just short 2.5 million light-years that away? I'm sure you see where this is going.

The Local Group is embedded within a much larger group known as the Virgo Supercluster, containing at least 100 galaxy groups and clusters. The rough center of the supercluster is in the constellation Virgo. Which as of right now, is that way, about 65 million light years away. Which certainly makes the 2.5 million light years to Andromeda seem like an afternoon jaunt in the family car.

Unsurprisingly, The Virgo Supercluster is a part of a larger structure as well. The Pisces-Cetus Supercluster Complex. This is a vast filament of galactic superclusters measuring about 150 million light years across AND a billion light years long. The middle is just over that way. Right over there.

One billion light years in length? Well that makes Andromeda seem right around the corner. So where are we? Where are you, and I and the Earth located in the entire Universe? The edge of the observable Universe is about 13.8 billion light years that way. But it's also 13.8 billion light years that way. And that way, and that way.

Andromeda Galaxy. Credit: Fabio Bortoli

And cosmologists think that if you travel in any direction long enough, you'll return to your starting point, just like how you can travel in any one direction on the surface of the Earth and return right back at your starting point. In other words, the Earth is located at the very, very center of the Universe. Which sounds truly amazing.

What a strange coincidence for you and I to be located right here. Dead center. Smack dab right in the middle of the Universe. Certainly makes us sound important doesn't it? But considering that every other spot in the Universe is also located at the center of the universe.

You heard me right. Every single spot that you can imagine inside the Universe is also the center of the Universe. That definitely complicates things in our plans for Universal relevance. And all this sure does make Andromeda seem close by….and it's still just right over there, at the center of the Universe. Oh, and about every spot in the universe being the center of the Universe? Well, we'll save that one for another episode.