Dwarf galaxy collisions make stars form in Milky Way

The Sagittarius dwarf galaxy has smashed through the galactic disc of the 10 000 times more massive Milky Way for the first time about six billion years ago. The collision caused ripples in the interstellar dust and gas of the at that time relatively quiet Milky Way. Two further collisions followed 2 billion and 1 billion years ago. According to findings of a paper published in the journal Nature Astronomy in May 2020, in the aftermath of each of these collisions the galaxy experienced a period of intense s