Stunning spiral galaxies may look serene, but in their dim outskirts there are signs of past violence: the shredded remains of other galaxies. Now a team of astronomers hope to figure out how common these remnants are. If they succeed, the survey could tell us more about the origin of galaxies like our own.
Spiral galaxies like the Milky Way are thought to bulk up in collisions and mergers with other galaxies. Simulations suggest this process will involve major mergers between equal-sized galaxies as well as the consumption of hundreds of dwarfs just a fraction of the size of our own.
Some of the best evidence of these “minor mergers” comes from the shredded remains of dwarf galaxies in the Milky Way’s own halo. The most prominent example is the Sagittarius stream, which wraps around the Milky Way and has been used to model the shape of the dark matter halo thought to surround our galaxy.
Full story: Hunting for scraps from galactic cannibal feasts