Photographing Spiral Galaxy NGC 7331
Using the 0.6-meter telescope at Williams College on the evening of 11/10/03, I took three five-minute-long exposures, each in a different part of the visible spectrum. I made the color image below by compositing those three exposures with the help of ImageJ and Photoshop. While not scientifically precise, the colors shown approximate the real visible color of the objects. The reddish area around the main galaxy is emitted by hot gas clouds which get their energy from the radiation of stars in the galaxy. The relative color between objects is especially reliable; for instance, the stars in the image range along a very noticeable scale from reddish to bluish (this is due to their differing temperatures).
image field I photographed is just northwest of the great square in the constellation
Pegasus (the winged horse). The main spiral galaxy visible in
my image is catalogued as NGC 7331 and
is estimated to be 46 million light-years away. (The light
used to make this photograph had been travelling through space for 46 million
Although the galaxy is tilted somewhat away from Earth, the spiral structure
is fairly easy to see.
is not bright
to make out with
the naked eye; it was first discovered in
galaxy in 1959. There are several more galaxies in the same region of the
sky as NGC 7331; the fuzzy object to the upper left is NGC
NGC 7337. In three dimensions, however,
NGC 7331 is probably nowhere near them.
desktop picture versions:
There is also a nebula photograph I manipulated.
A really nice photo of NGC 7331