Go out at 10 p.m. in late October face north and look straight up. You’ll see a square of stars (the Great Square of Pegasus). This marks the body of the horse. To the left (west) is the head and front legs.
You see, Pegasus is depicted as flying out of a cloud so we don’t get to see the entire winged horse. According to Greek myth, Pegasus was born out of the body of the headless Medusa (Perseus had just cut off her head). Pegasus flew off and was eventually captured by the hero Bellerophon.
Pegasus is the seventh largest constellation in our sky. Many of the brightest stars have Arabic names. For example; Markab (Alpha Pegasi), apparent magnitude 2.5, meaning the saddle of the horse; Scheat (Beta Pegasi), a semi-regular variable, magnitude 2.3 to 2.7, meaning the leg; Algenib (Gamma Pegasi), a Cepheid variable, meaning the flank; Enif (Epsilon Pegasi), meaning the nose. Markab, Scheat and Algenib form the great square.
Oops, but wait! It takes four stars to form a square! The fourth star is actually now known as Alpheratz (Alpha Andromedae), formerly known as Sirrah (Delta Pegasi) when it was part of Pegasus. In 1922, when constellation boundaries were set, Alpheratz\Sirrah was placed in the constellation of Andromeda.
Pegasus contains a Messier object (named after Charles Messier, a comet hunter who decided to catalog objects that were not comets), M15. Using binoculars, M15 can be found by using Enif (the nose of Pegasus) as a starting point, and scanning four degrees to the northwest of Enif.
M15 is a globular cluster easily seen with binoculars. It is one of the most densely packed globulars known. It might even have a central black hole. M15 is notable because it contains a large number of variable stars (112) and pulsars (eight rotating neutron stars). It also contains the first planetary nebula (Pease 1) discovered within a globular cluster (discovered in 1928).
Pegasus is noteworthy for another reason: It contains the first extrasolar planet (51 Pegai b) found around a sun-like star (51 Pegasi) 50 light years away. This planet is a hot Jupiter that orbits the star in four days. Its surface temperature likely exceeds 1,800 degrees Fahrenheit! 51 Pegasi, at magnitude 5.5, forms a very flat triangle between Alpha (Markab) and Beta Pegasi (Scheat). You’ll need at least binoculars to see it.
Another star, HR8799 is close to 51 Pegasi. HR8799 is 129 light years from Earth and also has exoplanets. Three of these planets have been directly imaged in 2008. There is a fourth planet, found after observations in 2009-2010 that is inside the orbits of the other three but still is 15 times farther from its sun than the Earth is from our sun.
Resource: HVA club
Heart of the Valley Astronomers is a group of amateur astronomers dedicated to sharing our passions for the night sky with the local communities in the central Willamette Valley of Oregon.
We meet on the second Tuesday of each month at the Walnut Community Room located the Scott Zimbrick Memorial Fire Station No. 5, 4950 NW Fair Oaks Drive, in Corvallis. Meetings are free and open to everyone.
We also regularly schedule star parties, technical assistance, astronomy classes through Corvallis Parks and Recreation and educational outreach for public and private groups. For more information see www.hvaastronomy.com, or look us up on Facebook.
Question of the Month
Last month: What two spacecraft are still going strong after 40 years in Space?
Answer: Voyager 1, launched on September 5, 1977, is in interstellar space 13 billion miles from Earth. Voyager 2, launched on August 20, 1977, is 11 billion miles from Earth. Both spacecraft are expected to last until about 2030.
This month: When is the Earth closest to the Sun?