Backyard stargazers get a monthly guide to the northern hemisphere’s skywatching events with “Tonight’s Sky.” In October, remnants of Halley’s Comet burn up in the Orionid meteor shower.
“Tonight’s Sky” is produced by HubbleSite.org, online home of the Hubble Space Telescope. This is a recurring show, and you can find more episodes — and other astronomy videos — at HubbleSite.org.
Stellarium is a free open source planetarium for your computer. It shows a realistic sky in 3D, just like what you see with the naked eye, binoculars or a telescope. It is being used in planetarium projectors. Just set your coordinates and go. http://www.stellarium.org/ You can use it to identify the sky in your neighborhood no matter where you live.
Highlights of the October Sky
Evening Planets:
Mars dips toward the southwestern horizon in the early evenings of October. It slips even closer to the horizon, and gets even harder to spot, later in the month.
Jupiter rises in the late evening to dominate the sky throughout the rest of the night. Use binoculars or a small telescope to admire the giant planet’s features.
Constellations and Deep-Sky Objects
Pegasus, the great winged horse of Greek mythology, prances across the autumn night sky. His body is denoted by a large area of stars known as the “Great Square.” Coordinates: Right Ascension: 22h Declination: +20º
Johannes Hevelius’ Pegasus fromUranographia(1690)
The story behind the name: Pegasus, the winged horse, was the son of Poseidon and Medusa. Medusa had been one of three beautiful sisters. Athena was angered that Medusa met with Poseidon in one of her temples. She changed Medusa into a terrible monster. Zeus kept Pegasus out of the world to placate Athena. Pegasus (and the warrior Chrysaor) sprang from Medusa’s body after she was killed by Perseus.
Pegasus had been living on Mount Helicon, tended by the Muses for whom he created a drinking well. Bellerophon, a young man accused of murder, fled his city and took refuge with Proteus, the king of Tiryns. Proteus suspected Bellerophon of trying to seduce his wife (not true) and sent him to his father-in-law, King Iobates, with a sealed note repeating the story. Iobates decided to set Bellerophon so difficult a task that he would would not return alive. He asked him to destroy the Chimaera, a fire-breathing monster with a lion’s head, a goat’s body, and a serpent’s tail. Bellerophon consulted a seer who advised him to catch and tame Pegasus. Some versions of the story say that the gods helped him, but in any case, Bellerophon caught and tamed Pegasus. He overcame the Chimera by flying above her and shooting her with arrows, and then forcing a lump of lead down her throat which melted from her fiery breath and burned her insides.
Pegasus hosts 51-Pegasi, the first Sun-like star known to have an extra-solar planet. The brightest corner of the Great Square, Alpheratz, is also the brightest star in the constellation Andromeda. In Greek mythology, this princess was chained to a rock near the sea to appease a sea monster.
Are we alone in the universe? Do other stars have planets too? Humanity took one step closer to answering these questions in October 1995 when it was announced that the star 51 Pegasi harbors at least one planet. In the above picture of 51 Peg the planet is not visible – it can only be detected by noticing small changes in the star’s motion. Claims of planetsorbiting other stars are rare, with perhaps the most credible pertaining to a neutron star - a star much different than the Sun. But new ground was broken in 1995 when the planetary detection claimed around the normal Sun-like star 51 Peg was confirmed. The planet, discovered by Michel Mayor and Didier Queloz, is thought to be like Jupiter - except orbiting so close to the parent star that it’s year lasts only about 4 days! In the above picture the lines centered on 51 Peg are caused by the telescope itself and are not related to the star or planet.
Within Andromeda’s boundaries, look for M31, the Andromeda Galaxy, an island of billions of stars. On a clear, dark night it appears as a faint smudge of light. Approximately 2.5 million light-years away, M31 is the closest spiral galaxy to our own Milky Way Galaxy and the most distant object you can see with your eyes alone. Binoculars and small telescopes reveal M31’s glowing nucleus and spiral arms.
Credit: NASA
A smaller companion galaxy, M110, appears as a faint spot near the large galaxy. The Andromeda Galaxy is slowly pulling in, and will eventually consume, another one of its small companion galaxies, M32.
Before sunrise, look for Venus blazing brilliantly above the eastern horizon.
Image credit: NASA/JPL
Events
An interesting meteor shower peaks on the night of October 21st to 22nd. After midnight, look to the east, where the constellation Orion is rising. Every few minutes you may spy a tiny remnant of Halley’s Comet burning up high in the atmosphere. This is the Orionid meteor shower.
The night sky is always a celestial showcase. Explore its wonders from your own backyard.
Video Credits
Produced by the Space Telescope Science Institute, Office of Public Outreach
Starfield images created with Stellarium
Mythological constellation forms from Firmamentum Sobiescianum sive Uranographia by Johannes Hevelius, courtesy of the United States Naval Observatory
Mars image courtesy of Matt Wedel
Jupiter image courtesy of Todd Gross
Andromeda Galaxy (M31) image based on an image courtesy of Naoyuki Kurita
Venus image courtesy of Mario Weigand
Narrated by Nancy Calo
Music written by Jonn Serrie
Production: Lucy Albert, Greg Bacon, John Bintz, John Godfrey, and Vanessa
Image credit: NASA/JPL 
