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.
This occasion means that the migration of stars to Andromeda and the galaxy’s development 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 internal 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.
The investigation was carried out by a global staff of astronomers utilizing Darkish Power 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 appear 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. “
Nearly all 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. Taking a look at relics of a earlier merger and stellar migration occasion in Andromeda might assist astronomers hunt for comparable artifacts in our personal galaxy.
“We have now by no means earlier than seen this so clearly within the motions of stars, nor had we seen a few of the buildings that outcome 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 internal halos of each galaxies are dominated by a single immigration occasion.”
To hint stellar migration within the galaxy, the staff turned to DESI as a result of reality that it’s the strongest multi-object survey spectrograph on this planet, able to measuring the spectra of greater than 100,000 galaxies in a single evening.
“This science couldn’t have been accomplished at another facility on this planet. DESI’s wonderful effectivity, throughput, and subject of view make it the perfect system on this planet to hold out a survey of the celebrities within the Andromeda Galaxy,” Dey added. “In just a few hours of observing time, DESI was capable of 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 continues to be capable of play a job in cutting-edge analysis like this thanks to 5 a long time of upgrades and enhancements.
The staff will now proceed to make use of the team-up between DESI and the Mayall Telescope to analyze stars positioned nearer to the sting of Andromeda. They hope this may additional reveal the galaxy’s construction and the immigration historical past of its stars.
“It is wonderful that we are able to 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,” staff 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 all the M31 halo with DESI. Who is aware of what new discoveries await!”
The staff’s analysis is revealed in The Astrophysical Journal (opens in new tab).
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