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Physics Photo of the Week

November 11, 2005

Edge-on Galaxy NGC 981

This distant galaxy is rather "unusual" in that it happens to be oriented edge-wise to our line of sight from our own Milky Way.  Notice the dark line right along the plane of the disk.  This dark strip is dust that lies between the stars in the plane of the galaxy and obscures the starlight from the billions of stars that exist in this galaxy.  New stars are constantly forming in this dust plane as density waves propagate through it. 

Our own Milky Way galaxy is a similar structure to this dust-laden disk.  The sun and planets are located about 1/3 the distance from the center to the edge in the plane of the disk.  When we see the Milky Way band across the sky on summer and fall nights away from the annoying city lights, we are looking through the disk of our own galaxy.  The dust lane in the Milky Way prevents us from seeing our galaxy center (in the constellation Sagittarius).  The stars that we see with our naked eyes in the night sky are located in a "small" sphere, much smaller than the diameter or thickness of our galaxy, but several hundred light years across.  See the diagram below.  All the stars in the foreground of the photo are stars within our own galaxy, relatively close to us compared to the size of our galaxy. 

Negative image of Galaxy

This image was photographed by Don Collins and the Astronomy Class at Warren Wilson College at the weekly viewing Thursday, Nov. 10.  It consists of a stack of 17 20 second exposures with a Meade DSI-Pro camera and a Celestron Ultima 2000 8-inch telescope.  The telescope was donated by Bernard Arghiere of Asheville, NC.

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 2005

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