Since the Universe is expanding, is it accurate to say that a galaxy is 5 billion light years away?

Since the Universe is expanding, is it accurate to say that a galaxy is 5 billion light years away?

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Isn't it better to say that the light from the galaxy took 5 billion light years to reach us and it is a very old picture of it? However, if light travelled back to the galaxy at the constant speed and an observer was stationed to record it wouldn't it take longer to reach because of the expansion of the Universe?

Also if it still exists after 10 billion years or not we could not predict. So is the picture of the Universe more of a timeline of events rather than like a conventional map that shows distance between points.

How do current day theories tackle these issues?

I'm not 100% sure if I'm understanding what your asking, but if your question could be rephrased as "how do we measure distances in an expanding universe?", then I can try to answer that.

Depending on what astronomers measure they use different distance measurements. For example the comoving distance between two objects takes into account the expansion, and so does not change with time. If you know the redshift of the galaxy, for example by measuring the spectrum, and have a cosmological model, then you can calculate the comoving distance. Here cosmological model means constraints on the amount of dark energy, matter (both dark and regular) and radiation. The current accepted model is that the universe is around 70% dark energy and 30% matter, most of which is dark (with negligible radiation). The percent here refers to the fraction of energy density. Note that these values change over time, mostly since dark energy is like a property of space and so increases as the universe expands.

For some more info see:

Note that light years is a definite measurement, and so we can use it a valid unit for all distance measures.

If The Universe Is Expanding, How Come Galaxies Collide?

If everything is expanding, how come our galaxy is on a collision course with the Andromeda galaxy?

The galaxies of this beautiful interacting pair bear some resemblance to musical notes on a stave. . [+] Long tidal tails sweep out from the two galaxies: gas and stars were stripped out and torn away from the outer regions of the galaxies. The presence of these tails is the unique signature of an interaction. ESO 69-6 is located in the constellation of Triangulum Australe, the Southern Triangle, about 650 million light-years away from Earth. Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

Everything is expanding - and so this is a natural question to ask. How can everything be expanding away from every other thing, and yet still collide?

Part of the blame for this confusion lies with the sorts of diagrams and language we use to demonstrate the expansion of the universe. If I say “the space between every galaxy is expanding, so that each galaxy appears to drift away from every other galaxy”, that’s a good way to get you to imagine an expansion of space. It also means that I’m ignoring everything else that’s going on that might be complicating the situation, to make the expansion of space idea as clear as possible.

In this case, what’s complicating the situation is our old friend gravity. If each galaxy in the universe were evenly spaced out - for instance, if they were all laid out as though they were points on a grid - then the simple description is also an accurate one. There wouldn’t be anything else going on. Each galaxy would continue to evolve in total isolation, slowly drifting farther away from anything else.

Numerical simulation of the density of matter when the universe was 4.7 billion years old. Galaxy . [+] formation follows the gravitational wells produced by dark matter, where hydrogen gas coalesces, and the first stars ignite. Image credit: V. Springel et al. 2005, Nature, 435, 629

This isn’t what our universe looks like. Our universe looks much more cobwebby than gridlike, with big knots of galaxies, and little filaments of galaxies stretching away from each knot. The big knots are galaxy clusters, and can hold thousands of galaxies. Their smaller counterparts, galaxy groups, have a few galaxies in them. Our own galaxy is in a small group, with Andromeda, and a bunch of very small dwarf galaxies.

These clusters and groups are what happens when galaxies form close enough to each other that gravity can pull them together. If a galaxy is close enough to another galaxy, and not moving too fast, gravity will prevent them from ever truly separating again. These galaxies may spend many billions of years falling towards each other, and will generally miss each other on the first attempted collision, so will spend many more billions of years falling back together for a second, and then perhaps a third attempt. Our galaxy and Andromeda are in the first fall together stage, which will probably take about 3 billion more years before it’s hard to disentangle our two galaxies.

This system consists of a pair of galaxies, dubbed NGC 3690 (or Arp 299), which made a close pass . [+] some 700 million years ago. As a result of this interaction, the system underwent a fierce burst of star formation. In the last fifteen years or so six supernovae have popped off in the outer reaches of the galaxy, making this system a distinguished supernova factory. Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

Fundamentally, the fact that we see galaxy collisions comes down to two things galaxies didn’t form on a grid, and the force of expansion of our universe is less strong than the force of gravity for galaxies which are near each other. If the force of expansion were much, much stronger than it is, then even gravity might not be able to pull galaxies together, and each galaxy really would be an island universe, isolated for all time. Fortunately for us, gravity still reigns supreme as long as the conditions are right.

A Galaxy Far,Far, Away

A while back in Nature a paper was published on the most distant confirmed galaxy discovered so far. 1 The galaxy, known as z8 GND 5296 has a measured redshift of 7.51. You can see the galaxy in the image above.

So just how far away is this galaxy? It depends on which distance you are talking about.

When determining the distance of far galaxies like this one, astronomers typically give the value purely in terms of its redshift, often known as z. To calculate the z redshift of an object, you look for an emission or absorption line you can identify, such as those of hydrogen. You then compare the observed wavelength of the line from the object with the standard (not redshifted) line. The difference between the observed and standard wavelengths divided by the standard gives you a number known as z.

If there is no redshift, then there is no difference between observed and standard lines, hence the z is zero. Redshift is thus given by a positive number, where the bigger the number the bigger the z. Technically there is no limit to the value z can have, but the highest we have observed is about z = 12. Bigger z also means greater distance. Because of the expansion of the universe, the light of a distant galaxy is redshifted more than the light of a closer galaxy. So the galaxy with the greatest redshift is the most distant.

The reason astronomers usually talk about redshift instead of distance is that the measured z is purely an observational result. Yes, we know that bigger z means greater distance, but the exact distance depends on the model you use for the universe. We know this model is relatively accurate for determining distances, but with z you don’t have to assume any model.

Since this particular galaxy has a z of 7.51, just how far away is it? The first thing you need to do is transform the redshift to the travel time of the light since it left the galaxy. Once the light left the galaxy, cosmic expansion meant the light redshifted while it travelled. Using the standard model of cosmology we can determine the light left z8 GND 5296 about 13.1 billion years ago.

You might think calculating the distance from that age is simple. After all the speed of light is a constant, and if it travelled 13.1 billion years it must be 13.1 billion light years away. But the universe has been expanding throughout its history, so that answer doesn’t work. We can’t even say that the galaxy was 13.1 billion light years away when the light left because the universe expanded while the light travelled. So the galaxy was actually closer than that when the light left.

The distance the galaxy was from us when the light began its journey can be calculated by what is known as the angular diameter distance. For this galaxy that turns out to be about 3.4 billion light years. That means the light from z8 GND 5296 began its journey 3.4 billion light years away, but due to the expansion of the universe took 13.1 billion years to reach us.

To calculate the distance of the galaxy now, you need to start with the fact that it was 3.4 billion light years away from us 13.1 billion years ago and calculate how much the universe has expanded since then. This is known as the comoving distance. This comes out to be about 29.3 billion light years.

So the light from z8 GND 5296 has a redshift of z = 7.51. That means the light left the galaxy 13.1 billion years ago when the galaxy was 3.4 billion light years away. It is now 29.3 billion light years away. That can be a bit hard to wrap your head around.

Which is yet another reason why astronomers focus on z.

Finkelstein, Steven L., et al. &ldquoA galaxy rapidly forming stars 700 million years after the Big Bang at redshift 7.51.&rdquo Nature 502.7472 (2013): 524-527. ↩︎

Hubble spots galaxy 13,200,000,000 light years from earth. Most distant object ever seen in the universe.

I feel like I've never really gotten a satisfactory answer to this, and I've wondered for a long time, so I'm hoping someone here on r/science can help me out. How is it possible that the light can have traveled to us for 13.2 billion years when the universe is only 13.75 billions years old. It just doesn't seem like the math works.

In other words how are we in a location 13.2 billion light years away from this early object only 13.75 billion light years after the creation of the universe? Wouldn't we have to be traveling super close to the speed of light away from it the entire time? The other object couldn't have been moving away because the light was emitted only 0.55 billion years after the big bang. If we were in that position wouldn't that make us on the very razor edge of the universe?

I'm hoping someone can explain this simply, it's always bothered me and I've never really researched it enough to understand.

It comes down to how we measure distance. When the light we're observing left that galaxy, the distance between it and our galaxy was much smaller. Over the intervening years, the universe expanded, which increased the distance that the light ended up having to travel. In the end, the total distance actually traveled by the light was about 13.2 billion light years.

Now, the light was moving toward us that whole time, while the distance between us and the other galaxy was expanding. What this means is that the distance between us and the galaxy right now (in our reference frame i.e., the so-called "proper distance") is actually quite a bit more than 13.2 billion light-years. If the calculator I used is to be trusted (and I don't see why it shouldn't be), it works out that the proper distance between us and the galaxy is about 31.7 billion light-years.

I think you are extending the "nothing faster than the speed of light" rule further than it applies. Nothing can travel through the universe faster than the speed of light, but the universe itself can. What I mean is this: suppose at the time of the big bang there are two close-by points (not too close though the example breaks down for a really small separation, but bare with me). As the universe underwent inflation, those two points could wind up much further apart than the speed of light would allow. This is because, during inflation, the expansion of space itself occurred faster than the speed of light (in some sense). Now that's not exactly what's occurring with this 13.2 billion light-year distant galaxy because it formed long after inflation ended, but the point is that when considering phenomena resulting from the expansion of spacetime, the speed limit set by c doesn't always apply.

Inflation. The universe seemingly expanded faster than the speed of light when it was young.

The universe may be larger than we can detect. We can only see as far as light has traveled. We see the light from the time it left. It's entirely possible there is light that has not gotten to us yet.

When the light first departed from it's origin, it was much closer (because the universe was smaller then). So if at that time the origin was only (say) 5 billion light years away, it has had enough time to reach us.

In the meantime the universe has expanded. However the light hasn't been pulled away - rather it has been stretched like a rubber band, which is why it's wavelength has increased - in other words the light has been redshifted. Individual photons themselves are immune to space dilation, however the radiation they create is affected.

Now we see the position as being some 13.2 Billion light years away, but it still only took (say) 5 billion years for the light to get here.

go to r/askscience. they'll get you an answer right away.

I came here to ask this. The answer is something like "space itself is expanding and therefore even though speeds faster than light are not possible, but distances that would correspond to such speeds, minus the fact of the expanding universe, are." So in other words, it's magic.

Basically yes, the relative velocity between two distant galaxies can exceed the speed of light. This isn't because either one of them is actually moving that fast, but because the universe is expanding and new space is appearing between them. The further you are apart, the more new space gets added, so distant objects are moving away from us very, very fast. It's probable that many galaxies are moving away from us faster than the speed of light, meaning their light will never reach us - they're permanently beyond our cosmic "horizon".

Light always travels at the same speed in any inertial frame of reference. It is the old story about cows in a field. If one cow is moving in the direction of a light beam and measures the speed it will be c. If another cow is moving in the same direction at twice the speed of the first it will measure the beam of light at c.

Wouldn't we have to be traveling super close to the speed of light away from it the entire time? The other object couldn't have been moving away because the light was emitted only 0.55 billion years after the big bang.

Speed is always relative. If some object moves at some speed relative to us then we move with same speed relative to it.

Distant objects are in fact moving very fast away from us, it is known as Hubble's law:

Hubble's Law is the name for the astronomical observation in physical cosmology first made by American astronomer Edwin Hubble, that: (1) all objects observed in deep space (interstellar space) are found to have a doppler shift observable relative velocity to Earth, and to each other and (2) that this doppler-shift measured velocity, of various galaxies receding from the Earth is proportional to their distance from the Earth and all other interstellar bodies.

So, further it away -- faster it moves, basically.

The explanation for it is rather convoluted:

In effect, the space-time volume of the observable universe is expanding (from a smaller past to a larger future) and Hubble's Law is the direct physical observation of this process, as it unfolds.

Astronomy's Future

From the belief that the Earth was the center of the universe to the understanding that our Sun is just one of hundreds of billions of stars that make up our own Milky Way, human knowledge traveled quite a journey between antiquity and the Renaissance. And like the great earthly explorers of the Renaissance, astronomers at the turn of the last century ventured further out than ever before, and found the universe a far larger place than anyone had previously imagined. Twentieth century astronomers discovered black holes lurking in the centers of galaxies, stars with the mass of a mountain compressed to the size of a sugar cube, colliding galaxies, exploding stars, and quasars - giant shining beacons of light with the output of over 1000 Milky Ways.

And as the early European explorers were soon followed by botanists, geographers, geologists, and surveyors who thoroughly and systematically explored the "New World," astronomers today are following the lead of the astronomical explorers of the last century, embarking on their own thorough and systematic exploration of the heavens.

The universe, however, does not give up its secrets easily. The Sloan Digital Sky Survey has come together through the hard work of astronomers around the world. Astronomers will use data from the SDSS to discover many more amazing things in the years to come.

Since the Universe is expanding, is it accurate to say that a galaxy is 5 billion light years away? - Astronomy

How do we know what we observe is x light-years away? When we say the sun we see ‘now’ is from 8 minutes ago, I understand that - since we already know the distance to the sun. How do we measure distances to other objects?

Great question! Measuring distances is a very important problem in Astronomy and it is very hard to do.

So first of all you are absolutely right distances and light-years are directly related, light-years are simply a convenient way to state a distance.

Let me give you three typical ways of how Astronomers can determine distances to other objects:

One way is to use our movement around the sun to see distant stars from a slightly different angle throughout the year. This leads to a small parallax of nearby stars which we can use to calculate the distance using some triangle geometry. See for example

Another way we measure distance directly is by knowing how bright something is intrinsically. Then we look at how bright it appears in the sky and the dimmer it is the further we are away from it. Just like a lamp appears darker the further you are away from it since the light spreads out more. We for example have a good understanding of the absolute brightness of some supernovae and some stars that oscillate in brightness (cepheid stars).

The first one works well for our neighboring stars. The second one also works for other somewhat nearby galaxies. To make this more accurate we usually use a distance ladder, where one type of measurement helps us make sure the next one that goes even further out is still accurate.

For super far away galaxies, i.e. their light was sent so long ago that a good fraction of the universe's history has passed since, we have another way. See as the universe expands, the light gets stretched: blue light becomes redder, red light becomes infrared, and so on. Since from decades of very detailed surveys of the sky, we have a pretty accurate model of the history of the universe we can relate how much the light has shifted to a distance in light-years. Here as an example is GN-z11 one of the most distant objects we know:

Image of GN-z11: (credit: Hubble Space Telescope, NASA, ESA)

Artist conception of how GN-z11 looked like when the light was emitted: (credit: Pablo Carlos Budassi)

We know this galaxy has to be rather blue, but it appears completely red when we observed it. This lets us calculate that its light has been traveling to us for 13.4 billion years (almost the entire age of the universe which is around 13.7 billion years). Since then the space in between has expanded so much that today this galaxy is around 32 billion light-years away from us.

Also as a reminder all of these methods have significant uncertainty associated, we can't do these measurements down to a meter. Usually, these methods are only accurate to a few percent.

If we could theoretically warp drive 14 billion light-years away, what would would we see looking towards the expanding galaxy?

You would see basically the same thing that you can see from here. We don't occupy a privileged position in the universe. The universe is expanding everywhere, including wherever you end up. So you can't look "towards" the expanding universe, you're always inside it. The idea that the universe looks basically the same from any particular spot within it is called the cosmological principle.

The observable universe seen from a spot 14 billion light years from Earth would definitely be different in the sense that the individual galaxies that you could see would change, but the trends in galaxy evolution over time and what you see as you look into the distant (early) universe would be the same. There is no evidence that the universe has an edge or finite spatial extent. The observable universe is limited because the universe hasn't always existed, so light has only had 14 billion years in which to travel to us, cutting us off from things that are further away.

Astronomers Find The Oldest, Most Distant Galaxy to Date

Since time immemorial, philosophers and scholars have contemplated the beginning of time and even tried to determine when all things began. It's only been in the age of modern astronomy that we've come close to answering that question with a fair degree of certainty.

According to the most widely-accepted cosmological models, the Universe began with the Bang Bang roughly 13.8 billion years ago.

Even so, astronomers are still uncertain about what the early Universe looked like since this period coincided with the cosmic "Dark Ages". Therefore, astronomers keep pushing the limits of their instruments to see when the earliest galaxies formed.

Thanks to new research by an international team of astronomers, the oldest and most distant galaxy observed in our Universe to date (GN-z11) has been identified.

The team, whose research was recently published in the journal Nature Astronomy, was led by Linhua Jiang of the Kavli Institute for Astronomy and Astrophysics and Prof. Nobunari Kashikawa of the University of Tokyo.

They were joined by researchers from the Observatories of the Carnegie Institution for Science, the Steward Observatory, the Geneva Observatory, Peking University, and the University of Tokyo.

Simply put, the cosmic Dark Ages began about 370 thousand years after the Big Bang and continued for another 1 billion years.

At this time, the only light sources were either the photons released before – which is still detectable today as the Cosmic Microwave Background (CMB) – and those released by neutral hydrogen atoms. The light of these photons is so shifted due to the expansion of the Universe that they are invisible to us today.

This effect is known as "redshift," where the wavelength of light is elongated (or "shift" towards the red end of the spectrum) as it passes through the ever-expanding cosmos on its way to reach us.

For objects moving closer to our galaxy, the effect is reversed, with the wavelength shortening and shifting towards the blue end of the spectrum (aka. "blueshift").

For nearly a century, astronomers have used these effects to determine the distance of galaxies and the rate at which the Universe is expanding. In this case, the research team used the Keck I telescope at Maunakea, Hawaii, to measure the redshift of GN-z11 to determine its distance.

The results they obtained indicated that it is the farthest (and oldest) galaxy ever observed. As Kashikawa explained in a University of Tokyo press release:

"From previous studies, the galaxy GN-z11 seems to be the farthest detectable galaxy from us, at 13.4 billion light years, or 134 nonillion kilometers (that's 134 followed by 30 zeros). But measuring and verifying such a distance is not an easy task."

Specifically, the team examined the carbon emissions lines coming from GN-z11, which were in the ultraviolet range when they left the galaxy and were shifted by a factor of 10 – to the infrared (0.2 micrometers) – by the time it reached Earth.

This level of redshift indicates that this galaxy existed as observed roughly 13.4 billion years ago – aka just 400 million years after the Big Bang.

At this distance, GN-z11 is so far that it defines the very boundary of the observable Universe itself! While this galaxy had been observed in the past (by Hubble), it took the resolving power and spectroscopic capabilities of the Keck Observatory to make accurate measurements.

This was performed as part of the Multi-Object Spectrograph for Infrared Exploration (MOSFIRE) survey, which captured the emission lines from GN-z11 in detail.

This allowed the team to produce distance estimates for this galaxy that were improved by a factor of 100 over any measurements that were previously made. Said Kashikawa:

"The Hubble Space Telescope detected the signature multiple times in the spectrum of GN-z11. However, even the Hubble cannot resolve ultraviolet emission lines to the degree we needed. So we turned to a more up-to-date ground-based spectrograph, an instrument to measure emission lines, called MOSFIRE, which is mounted to the Keck I telescope in Hawaii."

If subsequent observations can confirm the results of this latest study, then the astronomers can say with certainty that GN-z11 is the farthest galaxy ever observed. Through the study of objects like this one, astronomers hope to be able to shed light on a period of cosmic history when the Universe was just a few hundred millions of years old.

This period coincides with the Universe was beginning to emerge from the "Dark Ages", when the first stars and galaxies formed and filled the early Universe with visible light.

By studying these, astronomers hope to learn more about how the large-scale structures of the Universe subsequently evolved. This will be assisted by next-generation telescopes like the James Webb Space Telescope (JWST) – scheduled to launch on 31 October, 2021.

These instruments will even allow astronomers to be able to study the the "Dark Ages" itself, a time when the only non-CMB light was the spin line of neutral hydrogen – in the far microwave wavelength (21 cm).

To be able to probe the very beginnings of the Universe itself and watch as the first stars and galaxies form. What a time an exciting that will be!

The observations that made this research possible were conducted under the time exchange program between the Keck Observatory and the Subaru Telescope on Maunakea, Hawaii.

This article was originally published by Universe Today. Read the original article.

Since the Universe is expanding, is it accurate to say that a galaxy is 5 billion light years away? - Astronomy

A tiny section of the Hubble Ultra Deep Field captures a sprinkling of the estimated 10,000 galaxies visible in the image.

When we look out at space, we are looking back in time. The light arriving at our location from the farthest objects in the universe is light that left those objects billions of years ago, so we see them as they appeared long ago.

So what do we see, when we capture the light from these farthest objects? The most distant galaxies look strange – smaller, irregular, lacking clearly defined shapes.

No telescope before Hubble had the resolution to see these distant galaxies. Intrigued, astronomers turned Hubble on what appeared to be a nearly empty patch of sky and let it soak up all the light it could for 10 days. They were taking a risk – most Hubble observations take just hours, and the time being eaten up could have been used for more concrete needs. It was possible the objects the astronomers were looking for would be too faint or small for even Hubble to see.

But the results turned up a treasure trove: 3,000 galaxies, large and small, shapely and amorphous, burning in the depths of space. The stunning image was called the Hubble Deep Field.

In subsequent years, Hubble teamed with other observatories to examine small patches of the sky in high resolution, long exposures, and multiple wavelengths.

The deeper Hubble sees into space, the farther it gazes back in time. This chart illustrates the regions that have fallen under Hubble’s eye.

Surveys like the Hubble Ultra Deep Field (HUDF) and the Great Observatories Origins Deep Survey (GOODS) have provided pictures of vast, deep collections of galaxies – including some that existed when the universe was less than a billion years old.

The images allow us to follow the development of the universe. Tiny red dots -- early, shapeless galaxy building blocks whose light has been stretched by the expanding universe into an infrared glow – litter the most distant parts of the visible universe. Closer in, we see numerous galaxy interactions and collisions as galaxies come together and merge, growing in the process. And nearer still, we see versions of the large, stately galaxies we know today.

Related Links: Taking the Universe's Baby Pictures

Cosmic Birthday

Measuring Distances with Cepheids

The answer to the age of the universe is beaming down on us from the sky. We know the universe has been expanding since the Big Bang, so if we can measure its size and its expansion rate, we can extrapolate the age of the universe.

It's harder than it sounds. Since you can't extend a ruler out into the stars, all estimations are made by studying objects’ brightness. Cepheid variable stars are a special type of pulsing star whose cycles of intensity and dimness indicate their inherent brightness. When astronomers find Cepheid variable stars in galaxies, they compare how bright they truly are with how faint they appear over distance, and thus determine the distance to those galaxies. It's something like judging the distance to a car on a dark road by gauging the brightness of its headlights.

Before Hubble, astronomers had only been able to narrow the universe’s age down to 10-20 billion years old – not a particularly exact measurement with 10 billion years of leeway.

Hubble performed the definitive study of 31 Cepheid variable stars, helping to determine the current expansion rate and thereby narrow the age of the universe down to the most accurate it's ever been. Its observations of Cepheid variable stars in galaxies like NGC 4603, combined with measurements by other observatories, eventually pinned the age down to 13.7 billion years old, plus or minus a few hundred million years. Hubble’s observations helped change the age of the universe from a vast range of possibilities to the kind of number whose precision required a decimal point.

Knowing the age of the universe isn't just a matter of curiosity. By giving us a time scale for the development of stars and galaxies, it helps us refine our models of how the universe – and everything in it – formed.

Related Links: Cosmic Birthday

Lurking Black Holes

Quasars shine from both single (left) and colliding galaxies (right) in these images. The galaxies are 1.5 and 1.6 billion light-years away, respectively.

When astronomers first turned radio telescopes on the sky, they tracked radio wave sources to some typical cosmic objects, including the remains of supernovae, distant galaxies, and powerful areas of star birth. But one particular type of object looked like nothing more than a point of light, perhaps a star. Further observations showed that these objects were extremely far away, meaning they could only be distant galaxies. The objects, called "quasars," were thought to be the incredibly bright centers of those far-away galaxies.

The distance to quasars is so great, and their actual size so small – about the size of our solar system -- that the mere fact that we can see them via telescope makes quasars the brightest objects we've discovered in the universe. In fact, one of Hubble’s contributions to the quasar mystery was to prove with its high resolution there actually was a galaxy hidden behind the glare.

A supermassive black hole creates a jet of particles, traveling at nearly the speed of light from the center of galaxy M87. The jet bursts forth from the disk of material swirling around the black hole.

Hubble observations also helped determine that these brilliant galactic centers are powered by giant black holes. As matter falls into a supermassive black hole, the surrounding region heats up and releases tremendous amounts of energy and light, creating a quasar. Hubble found quasars in the centers of galaxies that are colliding or brushing up against one another, as well as in elliptical galaxies, which are thought to have developed as a result of multiple galactic mergers. These interactions may help "feed" the black hole and light up the quasar.

And it wasn't just quasars. Hubble found that almost all galaxies with bright, active centers have supermassive black holes feeding off the galaxy's matter. Further, the mass of the black hole is related to the mass of the bulge of stars around the center of the galaxy, indicating that the formation of a galaxy is closely connected to the formation of its black hole.

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