The Sagittarius dwarf's first passage
A satellite galaxy falls through the Milky Way's disk and sets off waves of new stars.
- When
- Known to
- ± 800 million years
- Era
- Enrichment, Stelliferous
The Sagittarius dwarf spheroidal makes its first plunge through the Milky Way's disk some five to six billion years ago. Gaia data show bursts of star formation coinciding with this and later passages, as the gravitational disturbance compressed gas across the galaxy. One of those bursts falls close to the age of the Sun, raising the possibility that our own Solar System exists because of a collision between galaxies.