January 5, 2015: The largest NASA Hubble Space Telescope image ever assembled, this sweeping view of a portion of the Andromeda galaxy (M31) is the sharpest large composite image ever taken of our galactic neighbor. Though the galaxy is over 2 million light-years away, the Hubble telescope is powerful enough to resolve individual stars in a 61,000-light-year-long section of the galaxy's pancake-shaped disk. It's like photographing a beach and resolving individual grains of sand. And, there are lots of stars in this sweeping view — over 100 million, with some of them in thousands of star clusters seen embedded in the disk. This ambitious photographic cartography of the Andromeda galaxy represents a new benchmark for precision studies of large spiral galaxies which dominate the universe's population of over 100 billion galaxies. Never before have astronomers been able to see individual stars over a major portion of an external spiral galaxy. Most of the stars in the universe live inside such majestic star cities, and this is the first data that reveal populations of stars in context to their home galaxy.
The panorama is the product of the Panchromatic Hubble Andromeda Treasury (PHAT) program. Images were obtained from viewing the galaxy in near-ultraviolet, visible, and near-infrared wavelengths, using the Advanced Camera for Surveys and the Wide Field Camera 3 aboard Hubble. This view shows the galaxy in its natural visible-light color, as photographed with Hubble's Advanced Camera for Surveys in red and blue filters July 2010 through October 2013.See the rest: