Physics Photo of the Week

Warren Wilson College

Dec. 10, 2004

M31 - The Great Galaxy in Andromeda.  Photo by Dan Sockwell.

M31 is the closest spiral galaxy to the Milky Way.  Even though it is relatively close in astronomical terms, it is over 2 Million light years distant from us.  That means that the light coming from this galaxy left it over 2 million years ago - that's 1000 times longer than the 2000 years since Jesus lived.  A galaxy such as M31 and our own Milky Way is characterized by the immense number of stars - about 100 billion (100 x 109) stars.  The dark strip on the right side of the central bulge is a major dust lane of the galaxy, and indicates part of the spiral structure.  This photo includes only the central part of the galaxy.  Wider field of view images show the disk of stars extending about twice teh distance from the center.  If this were the Milky Way, the sun would be just beyond the top or bottom of the image.  All the scattered stars that we see in the image are "field stars" in our own Milky Way galaxy.

Photographic details.  Physics assistant Dan Sockwell made this photo with a Canon 10D digital camera set on ISO-3200.  The camera allows prime focusing on a Celestron 8-inch Ultima Telescope (donated to WWC by Bernard Arghiere).  The image consists of 18 exposures of 30 seconds each.  These 18 frames are later aligned and stacked.  The image was further processed to enhance the contrast of the faint parts of the disk.  The central bulge (nucleus) of the galaxy is about 50 - 100 times brighter than the faint disk area in the bottom part of the photo.  Very soon we will be making further photographs of the galaxy, but using a wide field of view lens.  M31 covers a very large area of the sky.

M31 may be observed with binoculars on any clear dark night between October and February.  The galaxy is shown in the high-overhead part of the sky pictured at right.  Scan the area with binoculars, and you should see the faint, cloud-like appearance of the galaxy.  It is best to be away from city lights and to use a night when the moon is not visible such as this weekend (Dec 10-12, 2004).  If the weather is clear, the Physics Department will be making more photographs of the galaxy on the west side of Spidel Sunday, Dec. 12 8:30-9:30 pm.  You can ask any student in Astronomy Class at WWC for help!

Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department.  These photos feature an interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation.  Atmospheric phenomena are especially welcome.  Please send any photos to

Click here to see all Physics Photo of the Week for 2004.