In astronomy, the Arcturus Stream is a stellar stream which includes the nearby bright star Arcturus. It comprises many stars which share similar proper motion and so are physically associated.
This stream is not in the plane of the Milky Way galaxy and is likely a remnant of an ancient dwarf satellite galaxy, long since disrupted and assimilated into the Milky Way. It consists of old stars deficient in heavy elements.[1]
Research from the Radial Velocity Experiment at the Anglo-Australian Observatory headed by Quentin Parker was first to quantify the nature of the stream, though astronomers had known of its existence for some time. It was first discovered in 1971.[1]