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 appear to be physically associated.
This stream is not in the plane of the Milky Way galaxy and has been proposed as 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. However, Bensby and colleagues in analysing chemical composition of F and G dwarf stars in the solar neighbourhood found there was no difference in chemical makeup of stars from the stream, suggesting an intragalactic rather than extragalactic origin.
Research from the Radial Velocity Experiment at the Australian Astronomical 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.
Other members include the M-class stars 27 Cancri, Alpha Vulpeculae and RT Hydrae.