The Sloan Digital Sky Survey has revealed an overdensity of luminous red giant stars \sim 3 \arcdeg ( 40 projected kpc ) to the northeast of M31 , which we have called Andromeda NE .
The line-of-sight distance to Andromeda NE is within \sim 50 kpc of M31 ; Andromeda NE is not a physically unrelated projection .
Andromeda NE has a g -band absolute magnitude of \sim - 11.6 and central surface brightness of \sim 29 mag arcsec ^ { -2 } , making it nearly two orders of magnitude more diffuse than any known Local Group dwarf galaxy at that luminosity .
Based on its distance and morphology , Andromeda NE is likely undergoing tidal disruption .
Andromeda NE ’ s red giant branch color is unlike that of M31 ’ s present-day outer disk or the stellar stream reported by Ibata et al .
( 2001 ) , arguing against a direct link between Andromeda NE and these structures .
However , Andromeda NE has a red giant branch color similar to that of the G1 clump ; it is possible that these structures are both material torn off of M31 ’ s disk in the distant past , or that these are both part of one ancient stellar stream .