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
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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 dcollins@warren-wilson.edu.
Click
here to see all Physics Photo of the Week for 2005
Click
here
to see all Physics Photo of the Week for 2004.