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.