  M31 Great Andromeda Galaxy
by Robert GendlerAndromeda is the nearest major
galaxy to our own Milky Way Galaxy. Our Galaxy is thought to look much like
Andromeda. Together these two galaxies dominate the
Local Group of galaxies. The diffuse light from
Andromeda
is caused by the hundreds of billions of
stars that compose it. The several distinct stars that surround
Andromeda's image
are actually stars in
our Galaxy
that are well in front of the background object.
Andromeda is
frequently referred to as M31 since it is the 31st
object on
Messier's list of diffuse sky objects.
M31 is so distant it takes
about two million years for light to reach us from there. Although visible without aid, the above image of M31 is a digital mosaic of
20 frames taken with a small telescope. Much about M31
remains unknown, including how the center acquired
two nuclei.
M31 is a mosaic of 40 separate frames taken over 10 imaging sessions. Cumulative exposure time for the entire mosaic was 40 hours. Color data was obtained from previous images of M31 taken with various instruments. Each frame was imaged at a focal length of approximately 2000mm. The resolution of the individual frames varied from 1.7 to 2.5 arcseconds depending on sky conditions.
The equipment used was a 12.5" Ritchey Chretien Cassegrain (at F6) and ST10XME.
Selected NASA's Astronomy Picture the Day for November 26, 2006.
Text: APOD
Credit & Copyright:
Robert Gendler
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