Astronomers have found new proof that Andromeda, the galaxy subsequent door to our personal, grew by merging with one other galaxy. The occasion triggered a mass migration of stars into the galaxy.Â
This occasion means that the migration of stars to Andromeda and the galaxy’s progress historical past is similar to that of the Milky Way. Which means the findings have implications for our understanding of each galaxies.
The proof got here within the type of observations of the person motions of just about 7,500 stars within the interior halo of Andromeda. This confirmed these stars had begun their lives as a part of one other galaxy that merged with Andromeda round 2 billion years in the past.
Associated: The Andromeda Galaxy (M31): Location, Characteristics & Images
Scientists have lengthy predicted that enormous galaxies just like the Milky Way and Andromeda have grown to their present sizes by way of collisions and mergers all through their historical past, however the patterns within the motions of stars that would affirm this have been elusive.Â
The investigation was carried out by a global group of astronomers utilizing Darkish Vitality Spectroscopic Instrument (DESI) on the Nicholas U. Mayall 4-meter Telescope at Kitt Peak Nationwide Observatory, operated by NOIRLab.
“Our new observations of the Milky Way’s nearest giant galactic neighbor, the Andromeda Galaxy, reveal proof of a galactic immigration occasion in beautiful element,” lead researcher and NOIRLab astronomer Arjun Dey, stated in a statement (opens in new tab). “Though the evening sky could seem unchanging, the universe is a dynamic place. Galaxies like M31 and our Milky Way are constructed from the constructing blocks of many smaller galaxies over cosmic historical past. “
The vast majority of the celebrities within the Milky Way’s halo are additionally believed to have originated in one other galaxy discovering a brand new galactic residence throughout an enormous merger occasion thought to have occurred between 8 to 10 billion years in the past. relics of a earlier merger and stellar migration occasion in Andromeda might assist astronomers hunt for related artifacts in our personal galaxy.
“Now we have by no means earlier than seen this so clearly within the motions of stars, nor had we seen among the constructions that end result from this merger,” researcher co-author and College of Edinburgh astrophysicist, Sergey Koposov, stated within the assertion. “Our rising image is that the historical past of the Andromeda Galaxy is much like that of our personal galaxy, the Milky Way. The interior halos of each galaxies are dominated by a single immigration occasion.”
To hint stellar migration within the galaxy, the group turned to DESI because of the reality that it’s the strongest multi-object survey spectrograph on the earth, able to measuring the spectra of greater than 100,000 galaxies in a single evening.Â
“This science couldn’t have been finished at some other facility on the earth. DESI’s superb effectivity, throughput, and area of view make it one of the best system on the earth to hold out a survey of the celebrities within the Andromeda Galaxy,” Dey added. “In just a few hours of observing time, DESI was in a position to surpass greater than a decade of spectroscopy with a lot bigger telescopes.”
Regardless of first opening its eye to the universe in 1973, the Mayall Telescope remains to be in a position to play a task in cutting-edge analysis like this thanks to 5 many years of upgrades and enhancements.Â
The group will now proceed to make use of the team-up between DESI and the Mayall Telescope to research stars positioned nearer to the sting of Andromeda. They hope it will additional reveal the galaxy’s construction and the immigration historical past of its stars.Â
“It is superb that we will look out on the sky and skim billions of years of one other galaxy’s historical past as written within the motions of its stars — every star tells a part of the story,” group member and NOIRLab researcher Joan R. Najita stated. “Our preliminary observations exceeded our wildest expectations and we are actually hoping to conduct a survey of the complete M31 halo with DESI. Who is aware of what new discoveries await!”
The group’s analysis is printed in The Astrophysical Journal (opens in new tab).
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