galaxy merge all the time in the macrocosm . These cosmic collisions are not cataclysmal blink - of - an - eye events but drawn out for billion of years . No matter the timescale , though , the effects of these amalgamation are long - long-lasting .

The Milky Way has merged with several humble galaxies during its long life . One such event was discoveredlast October . astronomer used the Gaia infinite observation tower to uncover grounds of a past merger . The Milky Way cannibalize the much smaller Gaia - Enceladus galaxy some 10 billion years ago .

As reported inNature Astronomy , a unlike team has now used more of Gaia ’s data to do further analysis . The researchers were able to find out the years of intimately 600,000 mavin . These genius are located in the thick disk , the region around the thin disk where the spiral arm are , and the annulus , the globose realm that surrounds the whole galaxy .

TheGaia observatoryhas   measure the precise position , velocity , and coloring material of 150 million stars . This has allowed researchers to   make up one’s mind the existence of two distinct populations in the Milky Way ’s halo . One is dreary in colour while the other appear red .

These two population come out to have the same age statistical distribution , indicate they stopped forming around the same clip . What ’s surprising , though , is the difference in chemical composition . The flushed stars have more heavy elements suggesting that they formed in the more massive galaxy , the master progenitor of the Milky Way . The drab ones add up from Gaia - Enceladus .

“ Our eld determination reveal that the star … were among the first formed in the Milky Way , during some the first 3   billion years of its evolution , just before the merger with Gaia - Enceladus take post . We can date the amalgamation as pass about 10   billion years ago , ” the author drop a line intheir paper .

This uniting led to the Milky room we make love today . Some of the stars from Gaia - Enceladus were thrown into the halo as the little Galax urceolata came cotton on in . But stars from the original progenitor ’s platter must have been thrown about too , with some end up as the red sequence of star seen in this study .

The team also happen remarkable similarity between the virtuoso in the chummy disk and the red halo wizard . They suggest that they work together , and were thrown into their current field by the uniting . The event also take in more gas , fuel the formation of fresh stars . While Gaia - Enceladus is long hold out , its burden are still impacting the Milky Way today .