!Our neighbour, the Andromeda galaxy, devoured a large one 2 billion years ago
To grow, the galaxies merge together. Or rather, the bigger one eats the smaller one. Such episodes of galactic cannibalism have occurred repeatedly for the Andromeda galaxy. One theory is that it would have absorbed a large one 2 billion years ago. The proof !has just arrived
Visible toeyenaked in thenorthern hemisphereon nights devoid of light pollution , the Andromeda galaxy is our closest neighbour. Also called Messier 31 orNGC224, it currently stands at 2.55 millionlight yearsfrom the Sun, and is getting dangerously close to the Milky Way. To the point where the two will merge in about 4.6 billion years.
Throughout its existence, M31 has constantly interacted with its neighborhood through events that a recent study available on ArXiv dubs “galactic immigrations”. They designate thefusionwith other galaxies , when the bigger one swallows the smaller one. It is precisely these ancient galactic mergers that have interested an international team of researchers. Because it is possible to find traces of these episodes throughmovementsofstarswithin a galaxy, or their composition. This is the goal of the discipline known as “galactic archaeology”.
the andromeda galaxy will eventually merge with the milky way.
lorenzo comollithousands of stars that indicate a galactic merger 2 billion years ago
several hypotheses already exist on the past of m31, in particular one supposing a merger with another large galaxy 2 billion years ago, forming theandromeda galaxyas we know it today. named m32p, it would have been the third largest galaxy in the local group, after the milky way and andromeda. his remains would be in the inner halo of m31, precisely where theastronomers!
using the dark energy spectroscopic instrument , also called desi , the team studied more than 11,000 light sources in the direction of andromeda, thanks to almost 4 hours of exposure in the sky. the instrument, located on thetelescopemayall, arizona, was originally designed to map theuniversein order to measure the effect ofdark energyon its expansion. it is thus able to characterize many light sources in a short time.
the desi spectrograph tracks dark energy.
eca It confirmed the presence of approximately 7,500 stars of interest to researchers, across all identified sources. These were found to have many common characteristics, including significant metallicity. Meaning that the galaxy they came from “had a long history of star formation,” the study details, consistent with the idea of a massive galaxy. And confirming that "the substructure in the inner halo of M31 was produced by a single galactic immigration event 1 to 2 Gyr ago" , explain the researchers.
“We have never seen this so clearly in the motions of stars, nor had we seen some of the structures resulting from this merger ,” said Sergey Koposov, co-author of the study andastrophysicistat the University of Edinburgh. Our emerging picture is that the history of the Andromeda Galaxy is similar to that of our own galaxy, the Milky Way. The inner halos of bothgalaxiesare dominated by a single immigration event. »
the different episodes experienced by the sagittarius dwarf galaxy with the milky way.
esaA story similar to that of our Milky Way galaxy
This is the first time details of the ancient galaxy have been observed with such clarity, according to the study. "It's amazing that we can look up into the sky and read billions of years of another galaxy's history as written in the movements of its stars - each star tells a part of the story , concluded Joan R. Najita, co-author of the study and astronomer at NoirLab. Our initial sightings exceeded our wildest expectations and we now hope to investigate the entire M31 halo with DESI. Who knows what new discoveries await us”.
The researchers do not intend to stop there. Future surveys would make it possible to multiply the stars observed in the halo, and to cross-check its migratory history with even more details! As they remind us, knowing the past of our galactic neighbors is also essential to understanding how our future will unfold. Because the Milky Way, apart from its next merger with Andromeda, is also currently in the process of swallowing another: the dwarf galaxy of Sagittarius ! Some of this fusion already occurred around 5.7 billion years ago, leaving traces on some stars in the Milky Way. It should cross our galactic disc again within 100 million years, leading inevitably to itsabsorption.
Andromeda Galaxy: its violent past revealed
In our universe, galaxies grow by devouring dwarf galaxies that pass nearby. And according to a recent study, our neighbour, the Andromeda galaxy (M31) has, at least twice in the past, experienced violent episodes of cannibalism.
The Andromeda Galaxy (M31) is the closest and largest neighbor of our Milky Way. Astronomers estimate that the two will collide within four billion years. And in the hope of getting a clearer idea of the fate that will then be reserved for our galaxy, researchers from the University of Sydney (Australia) have been interested in the past of M31.
They studied its globular clusters , like remnants of ancient galactic collisions. “The stellar halo of the Andromeda galaxy is much larger and more complex than that of our Milky Way ,” remarks Dougal Mackey, astronomer at the Australian National University. What to imagine for M31, a violent past of true galactic cannibal.
a simulation of the collision that astronomers announce within four billion years between the andromeda galaxy and our milky way.
nasaTwo major bulimic episodes
Thus, the galaxy would have, over the past few billion years, swallowed several small galaxies. It even engulfed M32p, the third largest galaxy in our vicinity, after the Andromeda galaxy and the Milky Way . The Andromeda galaxy would also have experienced another bulimic episode 10 billion years ago, in the first moments of its existence.
The study also reveals two surprising facts. First that these two great episodes were fed by galaxies coming from different directions. Then that the oldest episode seems to be in the plan of the dwarf galaxies which orbit around M31. “Perhaps under the influence of the cosmic web [this vast network of filaments ofmaterialslinking galaxies] but this is pure speculation for the time being ,” concludes Geraint Lewis, an astronomer at the University of Sydney.
The Andromeda galaxy would have devoured a brother of the Milky Way
In the past, more than two billion years ago, there was a third major galaxy in our local group. But our neighbor Andromeda would have gutted her. After investigation, astronomers have just found his remains.
A lot has happened in our small local group of galaxies, a cluster of about fifty galaxies currently dominated by Andromeda and the Milky Way where we live. Currently, because the landscape continues to evolve. It will indeed be very different in three to four billion years, when the two mainspiral galaxieswill have merged, thus giving rise to Androlactée. Same thing in the past, other galaxies populated our environment and have since disappeared.
Long ago, life in its infancy on Earth had in the sky above it, the night thehazestarry star of the Milky Way and also, in all likelihood, another galaxy. Not a dwarf galaxy , like the Great and theSmall Magellanic Cloudthat we can admire today in the southern sky..., no, a larger galaxy, estimated at around 25 billionmassessolar. What has she become? It was on the side of Andromeda that astronomers found his trace after a real police investigation. Our neighbour, also called Messier 31 (M31), actually devoured it two billion years ago. Only a few pieces would remain today,scatteredaround. Incidentally, the intriguing satellite galaxyM32would constitute the largest visible remainder.
illustration of m32p, the ancient spiral galaxy before it was devoured by andromeda. two billion years later, only the visible bones would remain in the form of m32, satellite galaxy of the great m31, and probable former nucleus of m32p.
richard d'souza, eric bell, university of michiganM32, a small satellite galaxy like no other
Curious to clarify the true nature of M32, the team of researchers led by Richard D'Souza wondered whether this Andromeda satellite galaxy might not have been the victim of galactic cannibalism. Very compact, M32 does not look like adwarf galaxytypical, populated with stars, coming from the same star forge. Its population is more varied. “M32 is weird. Although it looks like a compact example of an oldelliptical galaxy, it actually has a lot of young stars, it's one of the most compact galaxies in the universe, there's not another galaxy like this," said Eric Bell, of the university. of Michigan, who co-authored this study just published in Nature Astronomy .
Their simulations show that the collision between these two large galaxies would produce effects that can be seen today, such as the population of stars in the halo of Andromeda, a long stellar current and finally M32, which would therefore be the remnant of the core of the butchered galaxy. Moreover, still according to their models, the event coincides with a period when Andromeda experienced great changes in its structure. "This interaction could explain the burst of star formation in M31 about 2 billion years ago, during which about one-fifth of its stars formed," the authors write . Another argument that supports this hypothesis.
The Andromeda galaxy, our neighbor located some 2.5 million light-years from our Milky Way, appears to be a real galactic cannibal, bulimic, devouring other galaxies.
Local Group Survey Team and TA Rector (University of Alaska Anchorage), NOAOOur neighbour, the Andromeda galaxy, devoured a large one 2 billion years ago!
To grow, the galaxies merge together. Or rather, the bigger one eats the smaller one. Such episodes of galactic cannibalism have occurred repeatedly for the Andromeda galaxy. One theory is that it would have absorbed a large one 2 billion years ago. The proof has just arrived!
Visible toeyenaked in thenorthern hemisphereon nights devoid of light pollution , the Andromeda galaxy is our closest neighbour. Also called Messier 31 orNGC224, it currently stands at 2.55 millionlight yearsfrom the Sun, and is getting dangerously close to the Milky Way. To the point where the two will merge in about 4.6 billion years.
Throughout its existence, M31 has constantly interacted with its neighborhood through events that a recent study available on ArXiv dubs “galactic immigrations”. They designate thefusionwith other galaxies , when the bigger one swallows the smaller one. It is precisely these ancient galactic mergers that have interested an international team of researchers. Because it is possible to find traces of these episodes throughmovementsofstarswithin a galaxy, or their composition. This is the goal of the discipline known as “galactic archaeology”.
The Andromeda galaxy will eventually merge with the Milky Way.
Lorenzo Comollithe andromeda galaxy will eventually merge with the milky way.
lorenzo comolliThousands of stars that indicate a galactic merger 2 billion years ago
Several hypotheses already exist on the past of M31, in particular one supposing a merger with another large galaxy 2 billion years ago, forming theandromeda galaxyas we know it today. Named M32p, it would have been the third largest galaxy in the Local Group, after the Milky Way and Andromeda. His remains would be in the inner halo of M31, precisely where theastronomers!
Using the Dark Energy Spectroscopic Instrument , also called Desi , the team studied more than 11,000 light sources in the direction of Andromeda, thanks to almost 4 hours of exposure in the sky. The instrument, located on thetelescopeMayall, Arizona, was originally designed to map theUniversein order to measure the effect ofdark energyon its expansion. It is thus able to characterize many light sources in a short time.
the desi spectrograph tracks dark energy.
eca It confirmed the presence of approximately 7,500 stars of interest to researchers, across all identified sources. These were found to have many common characteristics, including significant metallicity. Meaning that the galaxy they came from “had a long history of star formation,” the study details, consistent with the idea of a massive galaxy. And confirming that "the substructure in the inner halo of M31 was produced by a single galactic immigration event 1 to 2 Gyr ago" , explain the researchers.
“We have never seen this so clearly in the motions of stars, nor had we seen some of the structures resulting from this merger ,” said Sergey Koposov, co-author of the study andastrophysicistat the University of Edinburgh. Our emerging picture is that the history of the Andromeda Galaxy is similar to that of our own galaxy, the Milky Way. The inner halos of bothgalaxiesare dominated by a single immigration event. »
The different episodes experienced by the Sagittarius dwarf galaxy with the Milky Way.
Esathe different episodes experienced by the sagittarius dwarf galaxy with the milky way.
esaA story similar to that of our Milky Way galaxy
This is the first time details of the ancient galaxy have been observed with such clarity, according to the study. "It's amazing that we can look up into the sky and read billions of years of another galaxy's history as written in the movements of its stars - each star tells a part of the story , concluded Joan R. Najita, co-author of the study and astronomer at NoirLab. Our initial sightings exceeded our wildest expectations and we now hope to investigate the entire M31 halo with DESI. Who knows what new discoveries await us”.
The researchers do not intend to stop there. Future surveys would make it possible to multiply the stars observed in the halo, and to cross-check its migratory history with even more details! As they remind us, knowing the past of our galactic neighbors is also essential to understanding how our future will unfold. Because the Milky Way, apart from its next merger with Andromeda, is also currently in the process of swallowing another: the dwarf galaxy of Sagittarius ! Some of this fusion already occurred around 5.7 billion years ago, leaving traces on some stars in the Milky Way. It should cross our galactic disc again within 100 million years, leading inevitably to itsabsorption.
Andromeda Galaxy: its violent past revealed
In our universe, galaxies grow by devouring dwarf galaxies that pass nearby. And according to a recent study, our neighbour, the Andromeda galaxy (M31) has, at least twice in the past, experienced violent episodes of cannibalism.
The Andromeda Galaxy (M31) is the closest and largest neighbor of our Milky Way. Astronomers estimate that the two will collide within four billion years. And in the hope of getting a clearer idea of the fate that will then be reserved for our galaxy, researchers from the University of Sydney (Australia) have been interested in the past of M31.
They studied its globular clusters , like remnants of ancient galactic collisions. “The stellar halo of the Andromeda galaxy is much larger and more complex than that of our Milky Way ,” remarks Dougal Mackey, astronomer at the Australian National University. What to imagine for M31, a violent past of true galactic cannibal.
a simulation of the collision that astronomers announce within four billion years between the andromeda galaxy and our milky way.
nasaTwo major bulimic episodes
Thus, the galaxy would have, over the past few billion years, swallowed several small galaxies. It even engulfed M32p, the third largest galaxy in our vicinity, after the Andromeda galaxy and the Milky Way . The Andromeda galaxy would also have experienced another bulimic episode 10 billion years ago, in the first moments of its existence.
The study also reveals two surprising facts. First that these two great episodes were fed by galaxies coming from different directions. Then that the oldest episode seems to be in the plan of the dwarf galaxies which orbit around M31. “Perhaps under the influence of the cosmic web [this vast network of filaments ofmaterialslinking galaxies] but this is pure speculation for the time being ,” concludes Geraint Lewis, an astronomer at the University of Sydney.
The Andromeda galaxy would have devoured a brother of the Milky Way
In the past, more than two billion years ago, there was a third major galaxy in our local group. But our neighbor Andromeda would have gutted her. After investigation, astronomers have just found his remains.
A lot has happened in our small local group of galaxies, a cluster of about fifty galaxies currently dominated by Andromeda and the Milky Way where we live. Currently, because the landscape continues to evolve. It will indeed be very different in three to four billion years, when the two mainspiral galaxieswill have merged, thus giving rise to Androlactée. Same thing in the past, other galaxies populated our environment and have since disappeared.
SEE AS WELL
Andromeda galaxy: its formation finally elucidated
Long ago, life in its infancy on Earth had in the sky above it, the night thehazestarry star of the Milky Way and also, in all likelihood, another galaxy. Not a dwarf galaxy , like the Great and theSmall Magellanic Cloudthat we can admire today in the southern sky..., no, a larger galaxy, estimated at around 25 billionmassessolar. What has she become? It was on the side of Andromeda that astronomers found his trace after a real police investigation. Our neighbour, also called Messier 31 (M31), actually devoured it two billion years ago. Only a few pieces would remain today,scatteredaround. Incidentally, the intriguing satellite galaxyM32would constitute the largest visible remainder.
Illustration of M32p, the ancient spiral galaxy before it was devoured by Andromeda. Two billion years later, only the visible bones would remain in the form of M32, satellite galaxy of the great M31, and probable former nucleus of M32p.
Richard D'Souza, Eric Bell, University of Michiganillustration of m32p, the ancient spiral galaxy before it was devoured by andromeda. two billion years later, only the visible bones would remain in the form of m32, satellite galaxy of the great m31, and probable former nucleus of m32p.
richard d'souza, eric bell, university of michiganM32, a small satellite galaxy like no other
Curious to clarify the true nature of M32, the team of researchers led by Richard D'Souza wondered whether this Andromeda satellite galaxy might not have been the victim of galactic cannibalism. Very compact, M32 does not look like adwarf galaxytypical, populated with stars, coming from the same star forge. Its population is more varied. “M32 is weird. Although it looks like a compact example of an oldelliptical galaxy, it actually has a lot of young stars, it's one of the most compact galaxies in the universe, there's not another galaxy like this," said Eric Bell, of the university. of Michigan, who co-authored this study just published in Nature Astronomy .
Their simulations show that the collision between these two large galaxies would produce effects that can be seen today, such as the population of stars in the halo of Andromeda, a long stellar current and finally M32, which would therefore be the remnant of the core of the butchered galaxy. Moreover, still according to their models, the event coincides with a period when Andromeda experienced great changes in its structure. "This interaction could explain the burst of star formation in M31 about 2 billion years ago, during which about one-fifth of its stars formed," the authors write . Another argument that supports this hypothesis.
SEE AS WELL
Milky Way and Andromeda: collision in 4 billion years...
?In sum, astrophysicists have succeeded in elucidating two enigmas: the true nature of M32 and the consequences of Andromeda's interactions with another large galaxy. Understanding how this could have happened and how much the event could have disturbed the large spiral galaxy is important for researchers. Remember that this is what awaits us in three billion years (us, the Milky Way). The two galaxies are already on their collision course and hurtling towards each other at over 100 kilometers per second. So did in such a shockfrontal, the galaxies are shattered? Is it the same elsewhere, in the other clusters andsuperamasgalaxies in the universe
!The Andromeda galaxy as you've never seen it before
ThereNASAreleased the finest view of the Andromeda Galaxy (M-31) in theinfraredobtained by the space telescopeSpitzer.
See the " Galaxies " photo gallery (latest images of Andromeda)
This view is not that beautiful. It is full of details to help us better understand the tumultuous past of this galaxy, close to the Milky Way and located some 2 million light-years from us. Its appearance is unrecognizable compared to thewavelengthsof the seen. It shows the very structure of the galaxy, impossible to see in visible wavelengths. We see multiple asymmetries, a complex spiral structure and above all an off-center ring rich in star formation.
the andromeda galaxy (m31) seen in infrared (24 microns)
the andromeda galaxy (m31) seen in infrared (24, 70, 160 microns
This ring is no surprise to astronomers. But, if in the past it was always thought that it was part of the spiral structure of the arms, it is clear that this is not the case. The ring shows an opening at the exact location where they believe the dwarf galaxy M32 passed after crossing the Andromeda disk at highspeed.
This infrared image also shows dust andgasgalaxy interstellar. The central regions appear sharper where observation in the visible is difficult, if not impossible, due to the large concentration of stars.
The Spitzer Space Telescope
The Spitzer Space Telescope (infrared observatory) was placed onorbiton August 25, 2003 by arocketBoeing Delta II from the American base ofCap Canaveral(Kennedy Space Center). of adurationwith an operational life of at least 2 and a half years, likely to be extended to 5, Spitzer completes the range of NASA's large space telescopes, which areHubble,Chandraand Compton (desorbed in 2000).
From its orbitheliocentric,of thein the Sun, he will notably study the formation of stars and planets. It will observe the Universe as it was billions of years ago and should help scientists determine how and when the first objects formed, as well as their composition.
He will also be able to discover objects never observed before because hidden by theinterstellar dustlike the most distant stars and galaxies and will observe the coldest objects in theSolar system(outer planets,asteroidsand other small bodies) and dust disks present around young stars (proto-planetary disk).
The telescope is equipped with an 85 centimeter mirror and three cryogenically cooled instruments: a camera operating in the near and medium infrared, aspectrographefor analyzing all the infrared wavelengths and a photometer for collecting information on the far infrared range.
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