Hubble observes blue stars in Andromeda's core

The image at left shows the nearby, majestic Andromeda galaxy. The rectangular box marks the region probed by NASA's Hubble Space Telescope.

Hubble's view, taken with the Wide Field Camera 3 and the Advanced Camera for Surveys, is shown in the images on the right. The images are a blend of visible and ultraviolet light. The photo at top right is 7,900 light-years across and reveals the galaxy's crowded central region. The bright area near the center of the image is a grouping of stars nestled around the galaxy's black hole. The blue dots sprinkled throughout the image are ultra-blue stars whose population increases around the crowded hub. The blue stars are old Sun-like stars that have prematurely cast off their outer layers of material, exposing their extremely blue-hot cores. The square box outlines a close-up view of an area around the core.

The detailed image, shown at bottom right, reveals a richer population of blue stars huddled around the core. Dark dust clouds also are visible. The image is 740 light-years wide.

The right-hand images, taken with Hubble, are part of a census of stars in M31 called the Panchromatic Hubble Andromeda Treasury survey.

The image of the Andromeda galaxy was taken on 13 June 2001, with the WIYN/KPNO 0.9-meter Mosaic I by T. Rector and B. Wolpa of the National Optical Astronomy Observatory in Tucson, Arizona (USA).