M31 – Andromeda Galaxy

M31 – Andromeda Galaxy

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The Andromeda Galaxy is one of the most impressive galaxies to observe because of its size and distance — only about 2.5 million light years.  While comparative sizes have changed over the years, recent data suggests the Andromeda Galaxy is only slightly larger than the Milky Way in total mass, but contains about 1 trillion stars compared to our 200 or so billion in the Milky Way.  While most galaxies are moving away from us (measured by redshift) the Andromeda is moving towards us (blueshift) at the rate of 165 miles per second.  At this rate, it will collide/merge with the Milky Way in about 4 billion years.

Because of the apparent size of the galaxy — several degrees wide — it’s one of the few galaxies that don’t require high magnification to view and image.  M110 and M32, dwarf companion galaxies of M31, are easily spotted in the image and in the annotated version below.

M31 - The Andromeda Galaxy (Annotated)
M31 – The Andromeda Galaxy (Annotated)


Resolution ........ 1.592 arcsec/pix
Rotation .......... -112.579 deg (flipped)
Focal ............. 583.14 mm
Pixel size ........ 4.50 um
Field of view ..... 2d 18' 9.6" x 1d 32' 12.8"
Image center ...... RA: 00 42 34.057  Dec: +41 17 54.33