Hubble M31 PHAT+PHAST Mosaic

This is the largest photomosaic ever assembled from Hubble Space Telescope observations. It is a panoramic view of the neighboring Andromeda galaxy, located 2.5 million light-years away. It took over 10 years to make this vast and colorful portrait of the galaxy, requiring over 600 Hubble overlapping snapshots that were challenging to stitch together. The galaxy is so close to us, that in angular size it is six times the apparent diameter of the full Moon, and can be seen with the unaided eye. For Hubble's pinpoint view, that's a lot of celestial real estate to cover. This stunning, colorful mosaic captures the glow of 200 million stars. That's still a fraction of Andromeda's population. And the stars are spread across about 2.5 billion pixels. The detailed look at the resolved stars will help astronomers piece together the galaxy's past history that includes mergers with smaller satellite galaxies.

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