The Milky Way is a dynamic museum of ancient merging relics, river-like streams of stars stripped from dwarf satellite galaxies that flow through the galaxy revealing its history and structure that allow astronomers to better understand how galaxies in the universe have formed and evolved.
Remnants of Dwarf Satellite Galaxies
“Stellar streams are the remnants of dwarf satellite galaxies that are swallowed by the Milky Way, but have not been fully digested,” said Zhao Gang from National Astronomical Observatories of Chinese Academy of Sciences (NAOC). “The accretion process is not that the Milky Way swallowed the dwarf galaxy in one bite, but it peeled the dwarf galaxy layer by layer from outside to inside by tidal stripping, just like peeling an onion. The stripped stars distributed in their original orbits, and they formed a river-like structure, that is, a stellar stream.”