Triangulum may be a small constellation with dim stars, but it holds one gorgeous galaxy.
Triangulum is a constellation best seen in the fall. It lies to the left of the Great Square of Pegasus and below the "W" shape of Cassiopeia.
The small and somewhat dim shape of a triangle was seen by ancient Romans. The Romans saw Triangulum as Sicily, a nearby island that had a triangular shape. For ancient Hebrews, Triangulum was a "shalish," a musical instrument with three strings.
Major Stars of Triangulum
The key stars in Triangulum are the three that mark the corners of the triangle. The star Alpha Trianguli shines at magnitude 3.42. Alpha lies 64 light-years from Earth. Alpha stars are not always the brightest in constellations, and this is true for Triangulum. Alpha is only the second brightest star in this constellation. The next two stars in the corners of the triangle are close together. Beta and Gamma Trianguli lie 2 degrees apart. The pair lie a little less than seven degrees from Alpha. Beta Trianguli is the brightest star in Triangulum. Its magnitude is 3.0 and it lies 124 light-years away. Gamma Trianguli is magnitude 4.02 and lies 118 light-years away.
Galaxies of Triangulum: The Pinwheel
While there are a number of dim galaxies in Triangulum, there is really only one here that draws the attention of amateur astronomers. It is one of the brighter galaxies in the sky, the Pinwheel Galaxy. It is also sometimes called the Triangulum Galaxy because another galaxy with the same name (Pinwheel Galaxy) lies in Ursa Major. The Pinwheel Galaxy in Triangulum is also named M33 or NGC 598. M33 is just over four degrees from Alpha Trianguli, in the direction of the Great Square of Pegasus.
At magnitude 5.7, you can spot M33 through a steadily-held pair of binoculars under a dark sky. The face-on spiral galaxy is a beautiful sight through a telescope or in a photograph.
As far as galaxies go, M33 is rather close to us, at 3 million light-years distant. Thus we are seeing the galaxy not as it appears today, but as it did 3 million years ago, which is how long it took the light traveling from the galaxy to reach us.
M33 is part of the Local Group of galaxies. The Local Group is a family of galaxies to which the Milky Way, the Magellanic Clouds, and the Andromeda Galaxy belong.
Viewing M33
If you try to observe M33 through a telescope, it has low surface brightness, so make sure you are in a site without light pollution and your eyes have had a chance to adjust. You should see a bit of a brighter central oval shape and a dimmer glow smudged around it. See if you can make out any of its curving arms.
