[UnbelievingScumOnTheOtherSide]

I think you misunderstood the article, which is not referring to the visible portion of M31.

[sig226]

I understood it perfectly, although maybe I shouldn't use the word 'see.' Detect is more appropriate.

"Using the Mayall Telescope at Kitt Peak and the DEIMOS spectrograph on the the Keck II Telescope in Hawaii, the researchers found previously unseen red giant stars out to a distance of at least 500,000 light years from Andromeda's center.

The researchers picked out Andromeda's faint halo stars using a technique developed by Karoline Gilbert, a UCSC graduate student, which distinguishes the halo stars from the more numerous foreground stars in our Milky Way."