Heavenly Skies: Pegasus the Winged-Horse dances across the constellationsBy: Cindy Terpe, Special to the Telegraph
What child doesn’t know and love the white winged-horse with magical powers? The winged-horse named Pegasus is one of the most commonly known creatures in Greek mythology. Pegasus was the offspring of the god Poseidon and Medusa. After Medusa was killed by Perseus, Pegasus flew to Mount Helicon and struck the ground with his hoof, causing a spring to flow from that spot. This spring became sacred to the Muses (the goddesses of the inspiration of literature, science and the arts of ancient culture). Pegasus was then captured by the Greek hero Bellerophon. Pegasus allowed the hero to ride him on many dangerous missions. His rider, however, fell off his back trying to reach Mount Olympus, the home of the gods. Zeus then transformed the winged-horse into the constellation Pegasus and placed him up in the sky.
As summer ends and fall begins, we see the constellation Pegasus directly above us in the clear night sky. It was one of the 48 constellations listed by the second-century astronomer Ptolemy, and remains one of the 88 modern constellations. With the increasing light pollution of our time, it’s difficult to make out the stars that outline the shape of Pegasus. What you can see is the large asterism known as the Great Square of Pegasus which consists of four stars of nearly equal brightness that make a large square pattern. To find it, first use the Big Dipper to star-hop to Polaris, the North Star. By drawing an imaginary line from any Big Dipper handle star through Polaris, and going twice the distance, you’ll always land on the W or M-shaped constellation Cassiopeia the Queen. A line from Polaris through the end of the sharper side of the “W” of Cassiopeia will point you to the Great Square of Pegasus.
There are some notable deep sky objects that stargazers enjoy looking for in this constellation. One is the globular cluster Messier 15. Globular clusters are composed of thousands of stars that are very tightly bound by gravity, which gives clusters their spherical shapes and relatively high stellar densities toward their centers. They are among the oldest stars in the universe. Pegasus also has several galaxies within its boundaries. One galaxy is NGC 7331 a spiral galaxy that is 38 million light-years away from Earth. In spiral galaxies the central bulge typically rotates with the disk but the bulge in the galaxy NGC 7331 is rotating in the opposite direction to the rest of the disk. Another group of galaxies, known as Stephan’s Quintet is a cluster of five galaxies at a distance of 300 million light–years away. The Quintet is unique for its interacting galaxies. Two of the galaxies have clearly begun to collide, sparking massive bursts of star formation. It is predicted that four of the five galaxies may eventually merge into one large elliptical galaxy.
Visit the Cameron Park Rotary Club Community Observatory in Placerville for an enjoyable evening of stargazing and to learn more about the constellation Pegasus. It’s fun for all ages and free each clear Friday, Saturday and Sunday evening. Check our website communityobservatory.com for current operating hours and any unexpected closures. Don’t forget to like us on Facebook.
Cindy Terpe is the lead docent at the Cameron Park Community Observatory in Placerville.