A violent event on a colossal scale - the crash of two galaxies - may have paved the way for our solar system's birth. A star-formation binge in the Milky Way spanning the time when the solar system was born more than 4.5 billion years ago was apparently precipitated by the collision between our galaxy and a smaller one called Sagittarius, scientists said on Tuesday.
Such collisions typically do not involve stars smashing head-on, they said, but can foster conditions for star formation by, for example, amping up the amount of gas in a galaxy or having gas clouds come together.
The galaxies first crashed more than 6 billion years ago. Since then, Sagittarius - a "dwarf" galaxy 10,000 times less massive than the Milky Way - has twice passed through our galaxy's immense disk containing most of its roughly 100 billion stars. All three galactic interactions were associated with a burst of Milky Way star formation.