November 2012 Constellations of the Month: Pegasus and Andromeda
High in the sky and a little to the West are our November 2012 constellations of the month, Pegasus and
Andromeda. They are south and east of
last month's constellation, Cygnus,
and south and west of our Dec. 2011 constellation, Cassiopeia, "the W".
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. Here's a question which
will be answered next month: How many moons, side-by-side, would it take to
stretch across the sky in a line (arc) from the eastern horizon to the western
horizon?
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