The newly-announced shell structures are planes of stars curved, like umbrellas, left behind as the dwarf galaxy was torn apart, literally bouncing up and down through the center of the Milky Way as it was incorporated into our Galaxy, an event named the Virgo Radial Merger.
Computer modeling of the shells and the motion of the stars indicates that the dwarf galaxy first passed through the center of the Milky Way 2.7 billion years ago.
The finding poses potential implications for a number of other stellar phenomena, including the Gaia Sausage, a formation of stars believed to have resulted from the merger of a dwarf galaxy between 8 and 11 billion years ago.
“The Virgo Radial Merger opens the door to greater understanding of other phenomena that we see and don’t fully understand, and that could very well have been affected by something having fallen right through the middle of the Galaxy less than 3 billion years ago.â€.