Astronomy

Do most astronomers think that Andromeda will collide with Milky Way?

Do most astronomers think that Andromeda will collide with Milky Way?


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Most astronomers say it is likely to happen. Is this true? Are there any scientists that reject this?


Relatively high-resolution measurements were made with the Hubble Space Telescope over a 8 year period. From these measurements, astronomers determined that the collision was a certainty. It is predicted to occur in about 4 billion years. I suppose there may be some astronomers who disagree with the measurements or calculations but I can find no mention of that. The results were reported in an article in "Nature" (http://www.nature.com/news/andromeda-on-collision-course-with-the-milky-way-1.10765#/b1) and published in "Astrophysical Journal" Both are well-respected publications. The "Astrophysical Journal" reference is below.

Sangmo Tony Sohn; Jay Anderson; Roeland van der Marel (Jul 1, 2012). "The M31 velocity vector. I. Hubble Space Telescope proper-motion measurements". The Astrophysical Journal. doi:10.1088/0004-637X/753/1/7.


The Galactic Collision That Reshaped Our Milky Way

Roughly 10 billion years ago the Milky Way&mdashthen a smaller galaxy that did not contain its current spiral structure or diffuse halo of surrounding stars&mdashsuffered a massive head-on collision that shook it to its very core.

That is when our galaxy&rsquos gravity pulled a smaller companion, roughly one quarter its mass, into a dangerous dance: One where the dwarf galaxy plunged into and out of the Milky Way&rsquos disk, oscillating back and forth until it was finally swallowed whole. Although our galaxy survived, it has never been the same. The collision scrambled the orbits of stars in its disk, making it much puffier, and sent alien stars flying all around the Milky Way, thus building much of its halo. The smash up also funneled new gas toward the galactic center, adding fuel that mixed and mingled with the Milky Way&rsquos existing reservoirs to form new generations of stars.

Over time the dwarf galaxy faded away, but the scars from its collision never really disappeared&mdashnot that they have been easy to find. Astronomers, who have long thought the Milky Way likely grew from a vast number of merging dwarf galaxies, have struggled to uncover the signs of the largest mergers&mdashuntil today. Now a new paper published in Nature provides proof&mdashor something close to it. &ldquoIt&rsquos like uncovering a fossil or an archaeological piece of evidence for how the galaxy got started,&rdquo says James Bullock, an astronomer at the University of California, Irvine, who is unaffiliated with the new research.

Co-authored by Amina Helmi, an astronomer at the Kapteyn Astronomical Institute in the Netherlands, and her colleagues, the paper is one of a torrent following the long-awaited second data release from Gaia&mdasha spacecraft launched in 2013 by the European Space Agency to chart the heavens in unprecedented detail. Over the course of its mission Gaia has pinpointed the positions, motions, brightnesses and colors of 1.3 billion Milky Way stars with such accuracy that astronomers have used its data to craft new, exceptionally rich chapters in the biography of the Milky Way.

Indeed, after the second data set was released this April, many teams glimpsed hints of our violent history&mdashrecorded in stars that appeared out of place. Vasily Belokurov, an astronomer at the University of Cambridge, led a team that discovered a large number of stars moving out of sync with the galaxy&rsquos rotation, instead streaming toward or away from the galactic center against all expectations. Another Kapteyn astronomer, Helmer Koppelman, helmed a study that spotted a &ldquoblob&rdquo of stars orbiting in the opposite direction to most of the stars in the Milky Way&rsquos halo. And Misha Haywood, an astronomer at Paris Observatory, found fast-moving stars within the halo with atypical chemical abundances&mdasha sign they may have formed outside the Milky Way. &ldquoIt was really the tip of the iceberg,&rdquo Helmi says. Although all these studies blamed a past collision for such oddities, they disagreed over when the collision occurred, the mass of the satellite galaxy and whether the event involved a single large dwarf galaxy or several smaller ones. Helmi&rsquos study, on the other hand, brings multiple lines of evidence together to paint the most compelling portrait yet, says Kathryn Johnston, an astronomer at Columbia University who was not involved in the work. And it is one that relies on a single&mdashyet massive&mdashmerger.

Helmi and her colleagues analyzed 50,000 Gaia stars within the Milky Way&rsquos halo, finding 33,000 of them share similar amounts of angular momentum and orbit in the opposite direction than they should. &ldquoThat&rsquos when it became apparent that this was weird,&rdquo she says. &ldquoThe disk is ordered you have 100 million stars moving orderly around the galactic center. And then you have these stars that have decided to move in the opposite sense. That hints that these stars could not have been formed in the Milky Way.&rdquo To further test that hypothesis, the team also analyzed the chemical compositions of 600 of those stars previously studied with the ground-based APOGEE stellar survey. In every galaxy the abundance of elements heavier than hydrogen and helium gradually increases over time due to cycles of stellar death and rebirth. But the exact pattern of that increase is specific to each galaxy, much like a fingerprint. Taken together with simulations modeling the potential merger, the Gaia and APOGEE data reinforce the notion these stars are truly alien interlopers, suggesting they originated within a single large dwarf galaxy that ceased forming stars 10 billion years ago&mdashat the time it was cannibalized.

The team named the deceased galaxy &ldquoGaia&ndashEnceladus,&rdquo in honor of the space observatory and a being from Greek mythology, Enceladus, a giant who was believed to be buried under the Mount Etna volcano and responsible for the earthquakes in the region.

The study, if correct, firstly confirms what theorists have long thought: that galaxies like the Milky Way grow to enormous proportions by devouring many smaller ones. &ldquoIt wasn&rsquot known whether the Milky Way had experienced any mergers,&rdquo Helmi says. &ldquoAnd you never know when you see a merger in another galaxy, if it&rsquos just anecdotal. So, the fact that we now have the data, and it does tell us that mergers have happened and have had a significant impact in the history of our galaxy&mdashI think that&rsquos a very important step in confirming this picture that we have that galaxies do build up via mergers.&rdquo The sheer confirmation alone has sent many astronomers into a state of euphoria.

To boot, the study also presents an unprecedented opportunity for new avenues of research. Although astronomers have spotted galaxies merging in distant corners of the cosmos, a collision seen within the Milky Way&mdasheven just a remnant&mdashprovides a front-row seat that offers far more answers. Even our nearest neighbor, Andromeda, is too far off for robust studies of mergers there. &ldquoAt nearly three million light-years away, we&rsquore never going to Andromeda to populate it or study it in detail,&rdquo says Kim Venn, an astronomer at the University of Victoria in British Columbia who was not involved in the study. &ldquoThis is our only chance.&rdquo And with that chance, astronomers might better analyze the physics at play. Take the Milky Way&rsquos spiral disk of stars as an example. That disk is composed of two parts: a thinner, dense region encompassed by a thicker, more diffuse one&mdashbut no one knows how the thick disk arose. Although Helmi notes the collision in question heated and puffed part of the thin disk into a thick one, future simulations of the collision will help astronomers better answer that question.

And the answer will only further shed light on these galactic wrecks. Indeed, Helmi wants to use the Milky Way&rsquos evolution &ldquoas if it were a Rosetta stone&rdquo&mdashto better understand how galaxies across the universe evolve and how they affect the cosmos. The results might even help astronomers fathom a future collision close to home, Venn says, when the Andromeda galaxy smacks directly into the Milky Way some four billion years from now.


Light-years apart

It has long been known that the two galaxies have been heading in the general direction of each other.

They are separated by about 2.5 million light-years, but are converging at something like 400,000km/h (250,000mph). The new Hubble data provides fresh insight on when and how a union is likely to unfold.

This is possible because the orbiting observatory has measured in finer detail than ever before the motions of select regions of Andromeda, also frequently referred to by its catalogue name M31.

"It's necessary to know not only how Andromeda is moving in our direction but also what its sideways motion is, because that will determine whether Andromeda will miss us at a distance or whether it might be heading straight for us," explained Dr van der Marel.

"Astronomers have tried to measure the sideways motion for over a century. However, this was always unsuccessful because the available techniques were not sufficient to perform the measurement.

"For the very first time, we've been able to measure the sideways motion - in astronomy, also known as proper motion - of the Andromeda Galaxy using the unique observational capabilities of the Hubble Space Telescope."

Computer simulations based on Hubble's data indicate the two great masses of stars will eventually shape themselves into a single elliptical galaxy similar to the kind commonly seen in the local Universe.

However, although the galaxies will plough into each other, individual stars will not collide because the space between them will still be huge.

Nonetheless, the gravitational disturbance will shift the location of our Solar System, the researchers believe.

It is likely also that the merger will kick off a vigorous phase of new star formation as gas clouds are perturbed and collapse in on themselves. And the supermassive black holes at the centres of the galaxies will become one.

In addition, from their observations, the scientists say it is quite possible the Triangulum Galaxy (also known as The Pinwheel or M33), the next largest in the local group, will join the fray as well.

Whether anyone will be around to witness these events is an open question.

In four billion years' time, our star will be running low on its nuclear fuel and will have begun to swell, says Dr van der Marel.

"Due to the natural evolution of the Sun, it will get slightly hotter over time and a few billion years from now it will have got sufficiently hot to make life [on Earth] as we know it impossible," he told reporters.

"But since we are talking billions of years into the future, I personally do not think that means our civilisation will not be there.

"For example, if we find a smart way to use solar energy and turn it into air conditioning, we may still be able to live on this planet."


Milky Way Doomed to Crash with Andromeda

Four billion years from now, the Milky Way galaxy as we know it will cease to exist.

Our Milky Way is bound for a head-on collision with the similar-sized Andromeda galaxy, researchers announced today (May 31). Over time, the huge galactic smashup will create an entirely new hybrid galaxy, one likely bearing an elliptical shape rather than the Milky Way's trademark spiral-armed disk.

"We do know of other galaxies in the local universe around us that are in the process of colliding and merging," Roeland van der Marel, of the Space Telescope Science Institute in Baltimore, told reporters today. "However, what makes the future merger of the Andromeda galaxy and the Milky Way so special is that it will happen to us."

Astronomers have long known that the Milky Way and Andromeda, which is also known as M31, are barrelling toward one another at a speed of about 250,000 mph (400,000 kph). They have also long suspected that the two galaxies may slam into each other billions of years down the road. [ Milky Way Slams Into Andromeda (Artist Images)]

However, such discussions of the future galactic crash have always remained somewhat speculative, because no one had managed to measure Andromeda's sideways motion — a key component of that galaxy's path through space.

But that's no longer the case.

Van der Marel and his colleagues used NASA's Hubble space telescope to repeatedly observe select regions of Andromeda over a seven-year period. They were able to measure the galaxy's sideways (or tangential) motion, and they found that Andromeda and the Milky Way are indeed bound for a direct hit.

"The Andromeda galaxy is heading straight in our direction," van der Marel said. "The galaxies will collide, and they will merge together to form one new galaxy." He and his colleagues also created a video simulation of the Milky Way crash into Andromeda.

That merger, van der Marel added, begins in 4 billion years and will be complete by about 6 billion years from now.

A future cosmic crash

Such a dramatic event has never occurred in the long history of our Milky Way, which likely began taking shape about 13.5 billion years ago.

"The Milky Way has had, probably, quite a lot of small, minor mergers," said Rosemary Wyse of Johns Hopkins University in Baltimore, who was not affiliated with the new study. "But this major merger will be unprecedented."

The merger poses no real danger of destroying Earth or our solar system, researchers said. The stretches of empty space separating the stars in the two galaxies will remain vast, making any collisions or serious perturbations unlikely.

However, our solar system will likely get booted out to a different position in the new galaxy, which some astronomers have dubbed the " Milkomeda galaxy." Simulations show that we'll probably occupy a spot much farther from the galactic core than we do today, researchers said.

A new night sky

And the collision will change our night sky dramatically. If any humans are still around 3.75 billion years from now, they'll see Andromeda fill their field of view as it sidles up next to our own Milky Way. For the next few billion years after that, stargazers will be spellbound by the merger, which will trigger intense bouts of star formation.

Finally, by about 7 billion years from now, the bright core of the elliptical Milkomeda galaxy will dominate the night sky, researchers said. (The odds of viewing this sight, at least from Earth, are pretty slim, since the sun is predicted to bloat into a huge red giant 5 or 6 billion years from now.)

In its 22-year history, Hubble has revolutionized the way humanity views the cosmos. The new finding is another step in that process, researchers said.

"What's really exciting about the current measurements is, it's not about historical astronomy it's not about looking back in time, understanding the expansion of the universe," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate and a former astronaut who flew on three space shuttle missions that repaired Hubble .

"It's looking forward in time, which is another very human story," Grunsfeld added. "We like to know about our past — where did we come from? We very much like to know where we're going."


Light-years apart

It has long been known that the two galaxies have been heading in the general direction of each other.

They are separated by about 2.5 million light-years, but are converging at something like 400,000km/h (250,000mph). The new Hubble data provides fresh insight on when and how a union is likely to unfold.

This is possible because the orbiting observatory has measured in finer detail than ever before the motions of select regions of Andromeda, also frequently referred to by its catalogue name M31.

"It's necessary to know not only how Andromeda is moving in our direction but also what its sideways motion is, because that will determine whether Andromeda will miss us at a distance or whether it might be heading straight for us," explained Dr van der Marel.

"Astronomers have tried to measure the sideways motion for over a century. However, this was always unsuccessful because the available techniques were not sufficient to perform the measurement.

"For the very first time, we've been able to measure the sideways motion - in astronomy, also known as proper motion - of the Andromeda Galaxy using the unique observational capabilities of the Hubble Space Telescope."

Computer simulations based on Hubble's data indicate the two great masses of stars will eventually shape themselves into a single elliptical galaxy similar to the kind commonly seen in the local Universe.

However, although the galaxies will plough into each other, individual stars will not collide because the space between them will still be huge.

Nonetheless, the gravitational disturbance will shift the location of our Solar System, the researchers believe.

It is likely also that the merger will kick off a vigorous phase of new star formation as gas clouds are perturbed and collapse in on themselves. And the supermassive black holes at the centres of the galaxies will become one.

In addition, from their observations, the scientists say it is quite possible the Triangulum Galaxy (also known as The Pinwheel or M33), the next largest in the local group, will join the fray as well.

Whether anyone will be around to witness these events is an open question.

In four billion years' time, our star will be running low on its nuclear fuel and will have begun to swell, says Dr van der Marel.

"Due to the natural evolution of the Sun, it will get slightly hotter over time and a few billion years from now it will have got sufficiently hot to make life [on Earth] as we know it impossible," he told reporters.

"But since we are talking billions of years into the future, I personally do not think that means our civilisation will not be there.

"For example, if we find a smart way to use solar energy and turn it into air conditioning, we may still be able to live on this planet."


Comments

Measuring the proper motion of M31 is a remarkable achievement. It also repesents a new chapter in an old astronomical story.

In the early 1920s, Adriaan van Maanen measured proper motions in the "spiral nebulae." The angular velocities he found were so high that the nebulae couldn't possibly be external to our own galaxy.

Of course, these measurements were incorrect and are now regarded as one of the bigger blunders in astronomical history. After Edwin Hubble determined galactic distances, it became obvious that the proper motions of the spiral nebulae must be very small -- so small that it's amazing that this measurement has finally been accomplished.

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Interesting reading here. I have seen other reports in the past on M31 and Milky Way colliding some 4 billion years in the future. Always risky to predict the future. Another view of the future can be found in Revelation 21-22.

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Rod, one benefit of predicting the future 4 billion years hence is that there's little risk of being proven wrong during your own lifetime. When prophesying that "the end is near," it's always a good idea to leave yourself adequately ambiguous wiggle room.

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Nice comments all. Yes, Bob Sills, it is a very impressive accomplishment to have measured the proper motion of the Andromeda Galaxy. And Rod, I appreciate your referring to the vastly different outcome for the earth mentioned in the final two chapters of the Bible. (For a little more on the happy future of the earth and of mankind upon it see Psalms 37:9-11,29,34, 104:5, Ecclesiastes 1:4 & Matthew 5:5) And Anthony, I do in fact believe that the end is near, but I agree with you that it&rsquos unwise to make predictions as to when. The end that I&rsquom convinced is coming however will not be an &ldquoend of life as we know it&rdquo type of event, as shown by the above verses. I hope to survive this coming end, and then live on for a long, long time. I can't agree with all the pessimistic talk that everyone has just seen the last Venus transit of our lifetimes, or even that &ldquolife as we know it&rdquo has only a billion more years on this planet due to a warming sun. Due to the laws of physics it is very likely that the sun will in fact warm, but I have faith that God has a plan for dealing with this problem. I think it&rsquos very interesting timing that the predicted merger with Andromeda is forecasted to begin about a half a billion years prior to the sun&rsquos predicted red giant phase. When this &ldquocollision&rdquo occurs it will be more of a creative, rather than a destructive occurance, because a burst of star and planet formation will take place as gas and dust from the two galaxies merge. No one on earth knows, but perhaps the coming merger with Andromeda will provide a solution to the red giant sun problem for the earth and it&rsquos living payload. I know that probably the great majority who read this comment must think I&rsquom certifiably crazy, but be that as it may, I wanted to share my more hopeful point of view. I look forward to enjoying astronomy for, literally, forever.

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In rereading Kelley&rsquos article as well as my above post I see that the big galactic merger is expected to occur, not .5 billion years before the sun goes all red-giant on us, but a full billion years before the big bloat up. Even better than I first thought. A lot can happen in 10^9 years. How many times does the sun orbit the center of the Milky Way each billion years? About 4 or 5 times, I think. Lots of chances for close encounters with younger stars. Also note the optimistic projections for the sun&rsquos new location after the merger instead of being drawn inward toward the dangerous core of the new mega galaxy, &ldquothe simulations also suggest that our solar system will likely end up much farther from the galactic core than it is today.&rdquo More good news, and not just for us. I would infer that this would mean that the odds are good for most star systems in the habitable zones of any spiral galaxies undergoing galactic mergers. Seems like a superbly thought out Grand Design to me.


Astronomers use Gaia data to model Milky Way-Andromeda collision

Feb. 8 (UPI) -- Scientists have long suspected that the Milky Way and Andromeda galaxies are on a collision course, but now, thanks to new data from the European Space Agency's Gaia satellite, researchers finally know how fast and at what angles the two galactic bodies are approaching impact.

The Milky Way and Andromeda, along with the smaller Triangulum, are the three biggest galaxies in the Local Group, a collection of more than 54 galaxies -- most of them dwarf galaxies. While scientists think all 54 members are organized by their gravitational influence on one another, the positioning and trajectories of Local Group members isn't well understood.

"We needed to explore the galaxies' motions in 3D to uncover how they have grown and evolved, and what creates and influences their features and behavior," Roeland van der Marel, researcher at the Space Telescope Science Institute in Baltimore, said in a news release. "We were able to do this using the second package of high-quality data released by Gaia."

Launched in 2013, Gaia is working its way toward compiling the "book of the heavens" -- the largest and most precise 3D space catalog in history. At the culmination of Gaia's science mission, the space observatory will have surveyed a record 1 percent of the universe's 100 billion stars.

Through two data releases, the second of which occurred in April, Gaia has detailed the precise positions and movements of millions of stars.

For the latest research, scientists used data from Gaia's second release to better understand the dynamics of the Milky Way's galactic neighbors. Andromeda and Triangulum are located 2.5 and 3 million light-years from the Milky Way, but the duo are close enough to each that they are likely influencing one another's trajectories.

Astronomers used the latest Gaia data to more accurately characterize the relationship between the two galaxies.

"We combed through the Gaia data to identify thousands of individual stars in both galaxies, and studied how these stars moved within their galactic homes," said Mark Fardal, also of Space Telescope Science Institute. "While Gaia primarily aims to study the Milky Way, it's powerful enough to spot especially massive and bright stars within nearby star-forming regions -- even in galaxies beyond our own."

After combining the newest Gaia measurements with existing observations, researchers were able to model past and future orbital paths for each galaxy.

Previously, scientists surmised Triangulum is on one of two paths. A long orbital journey featuring several run-ins with Andromeda or a shorter track with no previous collisions. The latest models -- described by Fardal, Van der Marel and their colleagues in the Astrophysical Journal -- suggest Triangulum is on a shorter path and is in the midst of its first infall into Andromeda.

The new model showed Triangulum's influence on Andromeda will cause the larger galaxy to make a more glancing blow when it collides with the Milky Way. Updated simulations also determined the Milky Way-Andromeda collision will occur in 4.5 billion years, not 3.9 billion years as previously predicted.

"This finding is crucial to our understanding of how galaxies evolve and interact," said Timo Prusti, Gaia mission scientist. "Gaia was designed primarily for mapping stars within the Milky Way -- but this new study shows that the satellite is exceeding expectations, and can provide unique insights into the structure and dynamics of galaxies beyond the realm of our own. The longer Gaia watches the tiny movements of these galaxies across the sky, the more precise our measurements will become."


Crash of the Titans: Milky Way is destined for head-on collision with Andromeda Galaxy

NASA astronomers can now predict with certainty the next major cosmic event to affect our galaxy, Sun, and solar system: the titanic collision of our Milky Way galaxy with the neighboring Andromeda galaxy.

The Milky Way is destined to get a major makeover during the encounter, which is predicted to happen four billion years from now. It is likely the Sun will be flung into a new region of our galaxy, but our Earth and solar system are in no danger of being destroyed.

"Our findings are statistically consistent with a head-on collision between the Andromeda galaxy and our Milky Way galaxy," said Roeland van der Marel of the Space Telescope Science Institute (STScI) in Baltimore.

The solution came through painstaking NASA Hubble Space Telescope measurements of the motion of Andromeda, which also is known as M31. The galaxy is now 2.5 million light-years away, but it is inexorably falling toward the Milky Way under the mutual pull of gravity between the two galaxies and the invisible dark matter that surrounds them both.

"After nearly a century of speculation about the future destiny of Andromeda and our Milky Way, we at last have a clear picture of how events will unfold over the coming billions of years," said Sangmo Tony Sohn of STScI.

The scenario is like a baseball batter watching an oncoming fastball. Although Andromeda is approaching us more than two thousand times faster, it will take four billion years before the strike.

Computer simulations derived from Hubble's data show that it will take an additional two billion years after the encounter for the interacting galaxies to completely merge under the tug of gravity and reshape into a single elliptical galaxy similar to the kind commonly seen in the local universe.

Although the galaxies will plow into each other, stars inside each galaxy are so far apart that they will not collide with other stars during the encounter. However, the stars will be thrown into different orbits around the new galactic center. Simulations show that our solar system will probably be tossed much farther from the galactic core than it is today.

To make matters more complicated, M31's small companion, the Triangulum galaxy, M33, will join in the collision and perhaps later merge with the M31/Milky Way pair. There is a small chance that M33 will hit the Milky Way first.

The universe is expanding and accelerating, and collisions between galaxies in close proximity to each other still happen because they are bound by the gravity of the dark matter surrounding them. The Hubble Space Telescope's deep views of the universe show such encounters between galaxies were more common in the past when the universe was smaller.

A century ago astronomers did not realize that M31 was a separate galaxy far beyond the stars of the Milky Way. Edwin Hubble measured its vast distance by uncovering a variable star that served as a "milepost marker."

Edwin Hubble went on to discover the expanding universe where galaxies are rushing away from us, but it has long been known that M31 is moving toward the Milky Way at about 250,000 miles per hour. That is fast enough to travel from here to the Moon in one hour. The measurement was made using the Doppler Effect, which is a change in frequency and wavelength of waves produced by a moving source relative to an observer, to measure how starlight in the galaxy has been compressed by Andromeda's motion toward us.

Previously, it was unknown whether the far-future encounter will be a miss, glancing blow, or head-on smashup. This depends on M31's tangential motion. Until now, astronomers have not been able to measure M31's sideways motion in the sky, despite attempts dating back more than a century. The Hubble Space Telescope team, led by van der Marel, conducted extraordinarily precise observations of the sideways motion of M31 that remove any doubt that it is destined to collide and merge with the Milky Way.

"This was accomplished by repeatedly observing select regions of the galaxy over a five- to seven-year period," said Jay Anderson of STScI.

"In the 'worst-case-scenario' simulation, M31 slams into the Milky Way head-on and the stars are all scattered into different orbits," said team member Gurtina Besla of Columbia University in New York, N.Y. "The stellar populations of both galaxies are jostled, and the Milky Way loses its flattened pancake shape with most of the stars on nearly circular orbits. The galaxies' cores merge, and the stars settle into randomized orbits to create an elliptical-shaped galaxy."

The space shuttle servicing missions to Hubble upgraded it with ever more-powerful cameras, which have given astronomers a long-enough time baseline to make the critical measurements needed to nail down M31's motion. The Hubble observations and the consequences of the merger are reported in three papers that will appear in an upcoming issue of the Astrophysical Journal.


Galactic Collision, The Milky Way Is Going To Collide With The Andromeda Galaxy

“This photo illustration depicts a view of the night sky just before the predicted merger between our Milky Way galaxy and the neighboring Andromeda galaxy. About 3.75 billion years from now, Andromeda’s disk fills the field of view and its gravity begins to create tidal distortions in the Milky Way. The view is inspired by dynamical computer modeling of the future collision between the two galaxies. The two galaxies collide about 4 billion years from now and merge to form a single galaxy about 6 billion years from now.”

Four billon years from now, the Milky Way Galaxy, which we are located in, will collide with the neighboring Andromeda Galaxy. This is according to new research by NASA astronomers.

This collision will likely fling our solar system into a vastly different part of the Milky Way. The researchers say there is no danger of our solar system being destroyed in this collision though.

“Our findings are statistically consistent with a head-on collision between the Andromeda galaxy and our Milky Way galaxy,” said Roeland van der Marel of the Space Telescope Science Institute (STScI) in Baltimore.

The research was done using the Hubble Space Telescope. The Andromeda Galaxy is currently 2.5 million light years away but is being irreversibly drawn to the Milky Way through mutual gravitational attraction.

“After nearly a century of speculation about the future destiny of Andromeda and our Milky Way, we at last have a clear picture of how events will unfold over the coming billions of years,” said Sangmo Tony Sohn of STScI.

The researchers compare the collision to a batter in baseball watching a fastball come towards him — it will take some time but the trajectory is clear.

Computer simulations using Hubble’s data show that another 2 billion years after the first impact, the galaxies will completely merge into a single elliptical galaxy like the ones common in the local universe.

Although the galaxies will collide, the stars in them are so far apart that they will not collide. The orbits of stars around the galactic center will change though. Computer simulations suggest our solar system will be thrown much further from the galactic center than we are now.

The small galaxy that orbits Andromeda, the Triangulum Galaxy, will also join in the impact and possibly merge also. It may even impact first, before Andromeda.

“The universe is expanding and accelerating, and collisions between galaxies in close proximity to each other still happen because they are bound by the gravity of the dark matter surrounding them. The Hubble Space Telescope’s deep views of the universe show such encounters between galaxies were more common in the past when the universe was smaller.”

Only just a century ago, astronomers didn’t know that Andromeda was a separate galaxy. The vast distance between the two was ‘discovered’ by Edwin Hubble when he used a ‘variable star’ to serve as a measuring stick.

Andromeda is currently speeding towards the Earth at about 250,000 miles per hour. At that speed, you could reach the moon in an hour. This measurement was made by using the Doppler Effect, which is a change in frequency and wavelength of waves produced by a moving source relative to an observer.

“Previously, it was unknown whether the far-future encounter will be a miss, glancing blow, or head-on smashup. This depends on M31’s tangential motion. Until now, astronomers have not been able to measure M31’s sideways motion in the sky, despite attempts dating back more than a century. The Hubble Space Telescope team, led by van der Marel, conducted extraordinarily precise observations of the sideways motion of M31 that remove any doubt that it is destined to collide and merge with the Milky Way.”

“This was accomplished by repeatedly observing select regions of the galaxy over a five- to seven-year period,” said Jay Anderson of STScI.

“In the ‘worst-case-scenario’ simulation, M31 slams into the Milky Way head-on and the stars are all scattered into different orbits,” said team member Gurtina Besla of Columbia University in New York, N.Y. “The stellar populations of both galaxies are jostled, and the Milky Way loses its flattened pancake shape with most of the stars on nearly circular orbits. The galaxies’ cores merge, and the stars settle into randomized orbits to create an elliptical-shaped galaxy.”

The Hubble Space Telescope was recently upgraded with more powerful cameras. These upgrades have allowed these new calculations to be made.

The new research is set to be published in the Astrophysical Journal.


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Comments:

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