Free Astronomy Magazine March-April 2015

SPACE CHRONICLES Images were obtained from viewing the galaxy in near-ultraviolet, visi- ble, and near-infrared wavelengths, using the Advanced Camera for Sur- veys aboard Hubble. This view shows the galaxy in its natural visible-light colour as photographed in red and blue filters. This image is too large to be easily displayed at full resolu- tion and is best appreciated here www.spacetelescope.org/images/he i c1502a/ using the zoom tool. The image was presented at the 225 th meeting of the American As- tronomical Society in Seattle, Wash- ington, USA. n T his detailed image from the NASA/ESA Hubble Space Tele- scope shows a section of the An- dromeda Galaxy, Messier 31, and marks a few of the many features that are revealed within it. Several object types are labelled, includ- ing dust lanes, stellar clusters, Milky Way stars, and star-forming regions. [Image Credit: NASA, ESA/Hubble, and Z. Levay (STScI/AURA) - PHAT Brick Credit: NASA, ESA/Hubble, J. Dalcanton, B. F. Williams, L. C. Johnson (Uni- versity of Washington, USA) and the PHAT team] The Andromeda Galaxy is a large spiral galaxy — a galaxy type home to the majority of the stars in the Universe — and this detailed view, which cap- tures over 100 million stars, repre- sents a new benchmark for precision studies of this galaxy type. The whole galaxy contains over one thousand billion stars. The clarity of these observations will help astrono- mers to interpret the light from the many galaxies that have a similar structure but lie much further away. Because the Andromeda Ga- laxy is only 2.5 million light- years from Earth it is a much bigger target on the sky than the galaxies Hubble routinely photographs that are billions of light-years away. In fact its full diameter on the night sky is six times that of the full Moon. To capture the large portion of the galaxy seen here — over 40000 light- years across — Hubble took 411 images which have been assembled into a mosaic im- age. This panorama is the product of the Panchromatic Hubble Andromeda Treasury (PHAT) programme. T his wide-field view shows the Andromeda Galaxy (Messier 31) along with its companions M32 (below centre) and NGC 205 (upper right). The extend of the new PHAT survey of Andromeda using the NASA/ESA Hubble Space Telescope is shown by the irregularly shaped region and the main image presented here by the rectangle within it. [NASA, ESA, J. Dalcanton, B. F. Williams, L. C. Johnson (University of Washington, USA), the PHAT team, and R. Gendler]