Sunday, April 2, 2023

3939 - ANDROMEDA GALAXY - grew from galaxy mergers?

 

-   3939 -  ANDROMEDA  GALAXY  -  grew from galaxy mergers?  Astronomers have discovered new evidence that Andromeda, the galaxy next door to our own, grew by merging with another galaxy. The event triggered a mass migration of stars into the galaxy.


--------  3939  -  ANDROMEDA  GALAXY  -  grew from galaxy mergers?

-   These galactic collisions suggests that the migration of stars to Andromeda and the galaxy's growth history is very similar to that of the Milky Way. That means the findings have implications for our understanding of both galaxies.

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-    The evidence came in the form of observations of the individual motions of almost 7,500 stars in the inner halo of Andromeda. This showed these stars had begun their lives as part of another galaxy that merged with Andromeda around 2 billion years ago.

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-    Scientists have long predicted that large galaxies like the Milky Way and Andromeda have grown to their current sizes via collisions and mergers throughout their history, but the patterns in the motions of stars that could confirm this have been elusive.

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-   Although the night sky may seem unchanging, the universe is a dynamic place. Galaxies like M31 and our Milky Way are constructed from the building blocks of many smaller galaxies over cosmic history.

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-    The majority of the stars in the Milky Way's halo are also believed to have originated in another galaxy finding a new galactic home during a massive merger event thought to have occurred between 8 to 10 billion years ago.

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-   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 both galaxies are dominated by a single immigration event.

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-    To trace stellar migration in the galaxy, the team turned to “DESI” due to the fact that it is the most powerful multi-object survey spectrograph in the world, capable of measuring the spectra of more than 100,000 galaxies in a single night.

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-    This science could not have been done at any other facility in the world. DESI's amazing efficiency, throughput, and field of view make it the best system in the world to carry out a survey of the stars in the Andromeda Galaxy.  In only a few hours of observing time, DESI was able to surpass more than a decade of spectroscopy with much larger telescopes.

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-    Despite first opening its eye to the universe in 1973, the Mayall Telescope is still able to play a role in cutting-edge research like this thanks to five decades of upgrades and improvements.

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-    It's amazing that we can look out at the sky and read billions of years of another galaxy's history as written in the motions of its stars , each star tells part of the story.  Our initial observations exceeded our wildest expectations and we are now hoping to conduct a survey of the entire M31 halo with DESI. Who knows what new discoveries await!

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                   March 31, 2023    ANDROMEDA  GALAXY  -  grew from galaxy mergers?              3939                                                                                                                          

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--------------------- ---  Sunday, April 2, 2023  ---------------------------

 

 

 

 

         

 

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