APOD 2.6

Picture from December 9, 2010

This is the spiral galaxy M81, in the constellation of Ursa Major (the one with the Big Dipper). It's approximately 11.8 million light years distant, but is one of the brightest galaxies in Earth's night sky. Above and to the left, a dwarf companion galaxy to M81 called Holmberg IX can be seen. More intriguing, however, is the large faint loop structure on the right known as Arp's Loop. The loop was thought to be what is called a tidal tail, or a large band of material separated from M81 by nearby galaxy M82. Recent observations though show that Arp's Loop actually might not be too far from the Milky Way. The loop appears similar to clouds of dust observed just a few hundred light years above the plane of the milky way. Weird.

Observation 12/6/10

Tonight I observed Cassiopeia from my neighborhood's community center at about 7:50 PM. I was facing NNW, looking about 70 degrees up. Specifically, I observed the Worm Asterism, which from my position was visible in its classic "M" shape.

APOD 2.5

This galaxy, called M33, lies in the constellation of Triangulum. It is known more commonly as the Triangulum Galaxy or the Pinwheel Galaxy. It's over 50,000 light years across, making it the third largest galaxy in the Local Group (a collection of galaxies relatively close to our own), after the Andromeda Galaxy (M31) and the Milky Way. An interesting fact about the Triangulum Galaxy is that it is thought to be a satellite of the Andromeda Galaxy, in that it appears to revolve around the Andromeda Galaxy. Pretty hard to imagine an entire galaxy orbiting a whole other galaxy, eh? Also, that bright pink spot near the lower right is NGC 604, the brightest star forming region in the Triangulum Galaxy. The galaxy is actually a fairly important astronomical tool as well. Because of the measurements we have made of its variable stars, we can use it to measure distances across the cosmos.