Fred Barrett | Oct 03, 2018
The appearance of the constellation Pegasus in the east, marks the transition from summer to autumn. In Greek mythology, Pegasus was a winged horse possessed with magical powers. Pegasus, at 1100 square degrees, is the 7th largest constellation. When I say you will have no problems finding it, believe me, it is large and obvious. By mid October and around 9pm EDT in the evening, it is high and prominent in the south. It contains an asterism within its boundaries that is described as the Great Square of Pegasus. There are 4 stars that make up what looks like a box. Three of them are Beta, Alpha and Gamma Pegasi. The 4th is Alpha Andromedae. They are named Scheat, Markab, Algenib and Alpharatz respectively. The upper left star of the box or square has been transferred to the constellation Andromeda, just next door so to speak. Three of the stars are white, but Scheat is orange. It is a Supergiant variable M type star with a period of 38 days. It is 300 times more luminous than our Sun and 176 light years distant. Another star that is orange is Enif and it marks the horse’s muzzle. This star is a Supergiant K class variable 12 times the mass of the Sun and around 690 light years distant. Another interesting star is 51 Pegasi. It is fairly old at 8.5 billion years. It is a yellow/orange main sequence dwarf star very close to the mass of our Sun. It lies about 51 light years distant. In 1995, it was discovered that it has an exoplanet, a hot Jupiter (Bellerophon), orbiting it every four days. It is certainly difficult at any time to find DSO’s (Deep Space Objects) using binoculars but there are two near Pegasus that are binocular viewable. The first I will describe is M15. It is a Globular Cluster of stars not far from Enif. When you find it, you will notice that it’s centre is condensed. It was discovered in 1746 by the astronomer Maraldi while searching for a comet. M15 can be found by drawing a line from Biham (Theta Pegasi) to Enif (Epsilon Pegasi) and extending that line about 4 deg. M31 is a beautiful DSO that looks like a cotton ball. It can be resolved into a spiral with greater magnification using a telescope. To find the Andromeda galaxy, go from Alpheratz at the top left corner of the square to Mirach. Look to the right to find Mu (u). Go up at an angle to Gamma (v). A little to the right of gamma is the galaxy Andromeda. Andromeda has 2 satellite galaxies, M32 and M110. The larger galaxies usually have satellite galaxies that eventually are absorbed (eaten!) by their much larger neighbor. Astronomers have discovered stars that were from other small galaxies that were consumed by the Milky Way. The Milky Way and Andromeda are expected to collide in about 4.5 billion years and be absorbed into each other to make one much bigger Galaxy.
This month we have 2 meteor showers. The Orionid shower is active from Oct 2nd to Nov 7th. It peaks Oct 21st. This shower will be quite good, even though it peaks under a waxing gibbous Moon. If you want to stay up very late, (or get up very early) the Moon sets about 4am EDT. It’s peak rate is expected to be about 20 meteors per hour. The other shower, the Draconids, occurs on Oct 8/9. It is usually considered minor, but this year may be much more active. The comet that provides the debris that provides its meteors – 21P/Giacobini-Zinner, passed close to the Sun in September and this may have spawned much more debris. The hope is for about 10-15 meteors per hour.
Mars is still a fine sight in early October, but sheds half its beauty by the end of the month. Venus, Jupiter and especially Saturn, are well worth a look in the southwest after the Sun sets. Binoculars will provide a good view but a telescope really helps bring out detail.
Oct. 2: Last quarter Moon; Oct. 5: The Moon is at perigee (closest) - 364,265 km; Oct. 8: New Moon. Watch for the Draconid meteor shower; Oct. 14: The Moon passes 4 deg north of Saturn about 11pm EDT; Oct. 16: First quarter Moon; Oct. 17: The Moon is at Apogee (farthest) – 401,880 km; Oct. 21: Orionid meteor shower; Oct. 24: Full Moon. For reasons that are quite obvious, this full Moon is known as the Full Hunter’s Moon or the Full Harvest Moon. It’s the time to stock up on meat for the winter, bring in the harvest and be thankful; Oct. 31: Last quarter Moon. The Moon is also at perigee again – 368,064 km.
“The Beginner’s Observing Guide by Leo Enright is an invaluable companion for adventures in the sky. It also contains useful star charts. It can be ordered from the Royal Astronomical Society of Canada at www.rasc.ca/publications. A subscription to our very own excellent Canadian astronomy magazine “SkyNews” can be arranged at the RASC website as well.