November 2014 Constellations of the Month: Pegasus and Andromeda

High in the sky and a little to the West are our November 2014 constellations of the month, Pegasus and Andromeda.  They are east of July's constellation of the month, the Summer Triangle.

They look like a big square, with some appendages.  This is called the Great Square of Pegasus, even though the northeast star in the square belongs to Andromeda (which is why we needed to have 2 constellations this month).  Can you guess how many side-by-side Full Moons it would take to stretch across one side of the square? 

At the end of one of the appendages is the globular star cluster M15, which has about 100,000 stars.  Globular clusters, unlike other stars and clusters we see in our Milky Way galaxy, are not located in the disk of the galaxy.  They are found "above" and "below" (there is no direction which is "up" or "down" in space) the central part of the disk.  They formed before the rest of the galaxy took shape. 

Andromeda's stars are relatively faint, and they don't form a recognizable shape.  But the constellation has one major attraction – M 31, the Andromeda Galaxy.   It is a huge spiral galaxy which looks much like our own Milky Way.  It is bigger than the Milky Way and contains about a trillion stars, which is at least twice as many as the Milky Way.  It is bright enough to be seen with the naked eye.   It appears so bright, because it is so close -- only 2.5 million light years (16 trillion miles) away.  With the naked eye, it looks about as wide as 3 Full Moons.

... which brings us to the earlier question of how many Full Moons would stretch across a side of the Great Square – Answer: about 30.  That's a lot more than most of us would guess.  The Moon appears to us as about half a degree wide, and a semicircle across the sky from one horizon to the opposite horizon is 180 degrees.  So, about 360 Full Moons side-by-side would be required to traverse the sky from horizon to  horizon.