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We explore the stellar population of M31 in a Spitzer Space Telescope surveyutilizing IRAC and MIPS observations. Red supergiants are the brightest objectsseen in the infrared; they are a prominent evolutionary phase. Due to theircircumstellar envelopes, many of these radiate the bulk of their luminosity atIRAC wavelengths and do not stand out in the near infrared or optically. Goingfainter, we see large numbers of luminous asymptotic giant branch (AGB) stars,many of which are known long period variables. Relative to M33, the AGB carbonstar population of M31 appears sparse, but this needs to be spectroscopicallyconfirmed.

A point source survey of M31 with the Spitzer Space Telescope