WASHINGTON — The Milky Way, home to our sun and billions of other stars, merged with another smaller galaxy in a colossal cosmic collision roughly 10 billion years ago, scientists said on Monday based on data from the Gaia space observatory.
The union of the Milky Way and the so-called dwarf galaxy Gaia-Enceladus increased our galaxy’s mass by about a quarter and triggered a period of accelerated star formation lasting about 2 to 4 billion years, the scientists said.
“Yes, indeed it was a pivotal moment,” said astronomer Carme Gallart of Instituto de Astrofísica de Canarias in Spain, lead author of the research published in the journal Nature Astronomy.
Galaxies of all types including the Milky Way began to form relatively soon after the Big Bang explosion that marked the beginning of the universe some 13.8 billion years ago, but were generally smaller than those seen today and were forming stars at a rapid rate. Subsequent galactic mergers were instrumental in configuring galaxies existing now.