Star Constellation Facts: Pegasus, the Winged Horse

Star Constellation Facts: Pegasus, the Winged Horse

Pegasus is a handy July-to-January constellation (Northern Hemisphere) which you can use to locate other stars, constellations, and objects in the night sky. The rest of the time it lies below the horizon.

Seventh Largest Constellation

Pegasus is the seventh largest constellation, taking up nearly 1200 square degrees of space in the night sky; its location is simply right ascension 22 hours, declination 20°, because it is so large. Another way to locate it is to find the pointer stars in the Big Dipper, follow them right through Polaris over the top of the sky through Cassiopeia and down to the other side where you find Pegasus. It sits in an area of the sky that’s chiefly populated by dimmer stars, but has four reasonably bright stars of its own – Markab, Scheat, Algenib, and Alpheratz – which form The Great Square of Pegasus. Of the many stars in Pegasus, eight are known to have planets of their own. In fact other than our Sun, 51 Pegasi was the first star ever known to have a planet.

Named After Mythological Winged Horse

It was originally mentioned and enumerated by the Ptolemy in the second century and it’s one of the original 48 constellations that he wrote down. Of course it got its name from the famed winged-horse named Pegasus from Greek mythology, who was born after Perseus beheaded the gorgon Medusa and her blood mixed with seawater to create Pegasus. The horse was mortal but on the last day of its life, because of its lifelong service to Perseus and Andromeda, it was made into a constellation.

Useful In Locating Andromeda Galaxy

If you drew a line from the right star (named Markab) to the opposite left corner star (Alpheratz) of the great square of Pegasus and traveled about three quarters the width of the great square along that line, that is where you find the Andromeda Galaxy. Earth’s closest spiral galaxy sits a little more than 2 ½ million light-years away from our own planet and is structured very similarly to our own galaxy the Milky Way. In the same way that you cannot get a good look at the outside of your car when you’re sitting in it, we can’t get a good look at our own galaxy because we’re within it. That’s why it’s interesting to study one that is built similarly to our own. Well that and the fact that it’s on a direct collision course with our galaxy… (Don’t panic… it won’t happen for 4 billion years.)

Exploring The Constellation Pegasus

Contains One Of Oldest Globular Clusters.

In this constellation can be found one of the oldest globular clusters, Messier 15 (M15), which is around 12 billion years old and 33,600 light-years distant from Earth. M15 has more than 100,000 stars, including variable stars, pulsars and a double neutron star system, as well as being home to a planetary nebula.

Rich In Galaxies

Provided you look deeply enough in any part of the sky you’ll see thousands upon thousands of galaxies; and Pegasus has quite a number that aren’t too far away. The constellation has a preponderance of named galaxies in it, too, many of which have NGC numbers (New Galactic Catalogue). These include NGC 1 (the very first entry in the NGC), 7479, 7814, 23, 7673, 7217, 7331, 7742, 7315, 7078, 7725, 7753, and galaxies 7317-7320, also known as Stephan’s Quintet.

If you’ve been playing along with the home-version of our website, you know that there are 100 billion galaxies in the observable universe and 70 sextillion stars (70,000,000,000,000,000,000,000). The Sloan Digital Sky Survey has mapped a paltry 400,000 galaxies (see the video if you missed it) out of that number. To put the survey into perspective, remember that each one of those disks is a galaxy similar to our own, and it would take 30,000 to 120,000 years for light to cross each individual fuzzy patch.

Contains Einstein’s Cross

But even if Pegasus is rich in galaxies it has one thing that nobody else has: Einstein’s Cross! What you’re seeing here is a visual anomaly caused by gravity. In the center of the image is the galaxy NGC 7331; surrounding it are four identical quasars. Except that there’s actually only one – the same one – which is directly behind the galaxy from our point of view, so the gravity of the galaxy is bending the light of a single quasar around it on four different sides. If it wasn’t for this “gravitational lensing” we wouldn’t even be able to see that quasar. The galaxy itself is only 38,000,000 light-years away however the quasar behind it, one of the older objects in the universe, is eight billion light years away and much brighter than the galaxy. Intriguing, no?

Home To The Pegasids Meteor Shower

In any event, Pegasus can lay claim to one meteor shower, the Pegasids which occurs every year between 7th and 13th July, but it’s typically a weak shower which only produces around three meteors per hour. They are very fast, though, in the order of 45 miles per second (70 k/s) but in general the debris entering Earth’s atmosphere is very small, and no more than the size of a grain of sand.