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learnthesky.com and check out our online courses. Welcome my name is Janine and in this
video we will explore the constellation known as Pegasus. First let's look at
some of the mythologies that surround this constellation in Greek mythology.
Pegasus is a winged horse who is the son of the mortal Medusa and Poseidon. When
Perseus beheaded Medusa Pegasus and his brother emerged from her neck. Once born
he was taken in by the muses of Mount Olympus and raised there. One story of
Pegasus traces back to the Greek hero named Bellerophon. He captured Pegasus
and rode him in his fight with the Chimera. It was said that Bellerophon
attempted to fly with Pegasus to join the gods, but fell back to earth. Pegasus
however made the journey, then becoming a constellation and the servant of Zeus.
There are multiple myths and legends about Pegasus, and they vary from culture
to culture just like many of the constellation stories. Now let's identify
the distinctive pattern of Pegasus. The most obvious feature of Pegasus is the
great square which is outlined here. This shape dominates the sky in the autumn,
and it takes up a fairly large portion of the sky. This shape is also identified
as the asterism called the Great Square of Pegasus. Remember an asterism is not a
true constellation, but rather an easy-to-find shape within larger
constellations. They can be used as markers to help us find our way around
the sky. So here is a portion of the constellation Pegasus, and it represents
a winged horse, and is classified as a seasonal constellation.
Now Pegasus is a difficult constellation to get in a photograph
because it is so large, but here you can see the Great Square of Pegasus, and then
the head comes off this way, and two of the legs this way. Here's a picture of
Pegasus that I took with my camera phone and while the quality of it isn't that
great it's a good photo because it does show the entire constellation of Pegasus.
So before I point it out for you are you able to identify the Great Square
asterism that's right in the center of the photo. If you can then you should be
able to find the rest of the constellation. So here it is, we've got
the Great Square right in the center, and then the head that jets off right here,
and the two legs right here. Now Pegasus does share a star with the constellation
Andromeda, so you can start to see that constellation come off the Great Square
as well. Now that we know the pattern of Pegasus let's take a look at the bright
stars that sit within its boundaries. So as we take a look at the official star
map of Pegasus you hopefully can identify the Great Square, the two legs,
and then the head. The brightest stars are seated within the Great Square, so
let's take a look and zoom in there. The Alpha star is known as Markab and
it's an Arabic name that means 'saddle of the horse'. Alpha Pegasi is a B type giant
star, which means that its core has run out of hydrogen and it's beginning to
evolve beyond the main sequence ease of a star. It's in the southwest corner of
the Great Square and is estimated to be 133 light-years from Earth. So here is a
picture of the Great Square, and hopefully you can see it right in the
center. This is where Markab is. Betta Pegasi, named Scheat, is a
red giant star and the second brightest star in the constellation of Pegasus. Its
name is Arabic for 'upper arm' and it forms the upper right corner of the
Great Square. Its luminosity is 1500 times that of our own Sun.
Algenib it is the gamma star of this constellation. Its name is Arabic for 'the
flank' and it is a large star with almost nine times the mass of the Sun, and close
to five times the sun's radius. This star has also run out of hydrogen and is
starting to evolve out of the main sequence phase. Now let's examine the
celestial objects that sit within the boundaries of Pegasus. There's a galaxy, a
globular cluster, and a cosmic Mirage known as Einsteins cross. First let's
take a look at NGC 7331. It is a cluster of galaxies, but the main one is
this large spiral galaxy to the right of the image, and it's often referred to as
Milky Way's Twin because it's very similar in structure. There are a few
other satellite galaxies that surround this larger galaxy and if we zoom in
here you can see it's an unbarred spiral galaxy and it's estimated to be 40
million light years away.
Messier 15 is a globular cluster that sits within the boundaries of Pegasus. It
is estimated to be 33,600 light years away, and it is
one of the most densely packed globular clusters known in the Milky Way galaxy.
It is also one of the oldest, it has an estimated age of twelve to thirteen
billion years old, and it contains over 100 thousand stars.
Huchra's lens is the name of the lensing galaxy that's in front of the Einstein
cross. The galaxy is named for astronomer John Huchra. Here you can see that the
Lens quasar resembles a cross. So the gravitational force from the galaxy
creates four images of the quasar behind it. Amateur astronomers would be able to
see some of the cross using telescopes, but it would require extremely dark
skies and telescope mirrors with diameters of eighteen inches or more.
Let's review what we've learned about Pegasus the winged horse constellation.
It is best seen in the autumn months and it's classified as a seasonal
constellation. The best way to find it is to look for the asterism known as the
Great Square of Pegasus, which takes up a really large portion of the sky. In terms
of celestial objects that contains a few galaxies, globular cluster known as
Messier 15 ,and a cosmic Mirage known as Einstein's cross. I wish you luck finding
this constellation, and if you have any questions or comments be sure to leave
them in the spot below. I also want to send a huge thank you to David Cochrane.
for allowing me to use his amazing photographs for my videos! Be sure to
check him out on Twitter. Good luck finding Pegasus!