Andromeda Galaxy

Astronomers have divided imagery of the Andromeda galaxy taken by NASA’s Hubble Space Telescope into thousands of squares 300 light-years on a side and determined the history of star formation within each parcel to gain a comprehensive view of the galaxy’s past. This image highlights two such regions. Massive stars are bluer and short-lived, while less massive stars are redder and longer-lived. As a result, areas that have experienced recent star formation (1) tend to have a larger fraction of blue stars, while areas with less recent star formation (2) typically have a redder population.

About the colours

This image is a composite of separate exposures acquired by the ACS instrument on the Hubble Space Telescope. Several filters were used to sample broad wavelength ranges. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are: Blue: F475W (g) Yellow: F814W (I)

About the data

Data of M31 were obtained from the HST PHAT and PHAST Treasury proposals: P.I. J. Dalcanton and B. Williams (University of Washington) et al. 12058, 12073, 12109, 12107, 12074, 12105, 12113, 12075, 12057, 12111, 12115, 12071, 12114, 12072, 12056, 12106, 12059, 12108, 12110, 12112, 12055, 12076, 12070, 16778, 16778, 16796, 16796, 16797, 16797, 16798, 16798, 16799, 16799, 16800, 16800, 16801