He notes it could be part of the Sagittarius stream, a remnant of the Sagittarius dwarf galaxy, long assumed to be one of the building blocks of our own Milky Way.
FORBES: Astronomers Confirm Milky Way's Most Distant Stellar Stream
2.
Or the Gemini stream could be a remnant of another as yet undetected dwarf galaxy still in the process of being torn asunder by gravitational tidal interactions within our own Milky Way.
FORBES: Astronomers Confirm Milky Way's Most Distant Stellar Stream