Did galactic crash trigger solar system formation?
EarthSky in SPACE | June 4, 2020

The formation of the sun, the solar system and the subsequent emergence of life on Earth may be a consequence of a collision between our galaxy – the Milky Way – and a smaller galaxy called Sagittarius.


The Sagittarius dwarf galaxy has been orbiting the Milky Way for billions of years. As its orbit around the 10,000 times more massive Milky Way gradually tightened, it started colliding with our galaxy’s disk. The three known collisions between Sagittarius and the Milky Way have, according to a new study, triggered major star formation episodes, one of which may have given rise to the solar system. Image via ESA.
The formation of the sun, the solar system and the subsequent emergence of life on Earth may be a consequence of a collision between our galaxy, the Milky Way, and a smaller galaxy called Sagittarius, discovered in the 1990s to be orbiting our galactic home. That’s according to a new study published May 25, 2020, in the peer-reviewed journal Nature Astronomy.

Astronomers have known that Sagittarius repeatedly smashes through the Milky Way’s disk, as its orbit around the galaxy’s core tightens as a result of gravitational forces. Previous studies suggested that Sagittarius, a so-called dwarf galaxy, had had a profound effect on how stars move in the Milky Way. Some astronomers even claim that the 10,000 times more massive Milky Way’s trademark spiral structure might be a result of the at least three known crashes with Sagittarius over the past six billion years.

The new study, based on data gathered by ESA’s galaxy mapping Gaia spacecraft, revealed for the first time that the influence of Sagittarius on the Milky Way may be even more substantial. The ripples caused by the collisions seem to have triggered major star formation episodes, one of which roughly coincided with the time of the formation of the sun some 4.7 billion years ago.