CFHT, Current Image of the Week


December 6th, 1999

The Andromeda Galaxy and its Satellite NGC 205

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The Andromeda Galaxy and its Satellite NGC 205
Credit: Image courtesy of J.C. Cuillandre, CFHT

This image of Messier 31 and NGC 205 obtained at CFHT prime focus with CFH12K, a CCD mosaic of twelve 2,048 by 4,096 pixel CCDs, covers 42 by 28 square arcminutes (the full field of view of the camera): more than one time and a half the size of the full moon. Only a reduced portion of the nearby spiral galaxy Messier 31 and one of its satellite, the dwarf elliptical galaxy NGC 205, can be captured on a single frame though. The actual image size is 12,288x8,192 pixels, more than 100 million pixels total, with a pixel scale of 0.2 arcsecond per pixel. Such resolution allows resolving Messier 31 and NGC 205, only 2 million light years away, into individual stars (hundred of thousands on this image!). Messier 31 is the largest galaxy from the Local group, it is a spiral seen from our galaxy with an angle of approximately 10 degrees. The spiral arms are traced in this image with dust absorption and star formation (the blue areas are star forming areas, a higher resolution version of this image would show the blue stars individually). Note the bridge of matter (stars) between the two galaxies and the pinpoint appearance of NGC 205's core.

Technical description: This true color image [B-band (40mn), V-band (20mn) and R-band (10mn)] was obtained from a set of dithered exposures processed with the FLIPS package: the gaps and CCD artifacts have been removed. Observed on the third of September 1999.

next week: Thermal Inertia of Saturn's Ring Particles

editors: François Ménard & Jean-Charles Cuillandre
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CFHT is funded by the Governments of Canada and France, and by the University of Hawaii.