The Sky This Week, 2012 November 13 - 20
Messier 45, the Pleiades, imaged 2012 January 25
The Moon returns to the evening sky this week, first appearing low in the southwestern sky before working her way into the dim autumnal constellations. Skywatchers with low southwest horizons may just be able to catch the sliver of a day-old lunar crescent half an hour after sunset on the 14th, but you’ll have a much easier time spotting Luna on the following evening. She will wax to First Quarter by the end of the week. The phase will occur on the 20th at 9:31 am Eastern Standard Time. Try to spot ruddy Mars near the Moon on the evenings of the 15th and 16th. The planet will be seven degrees east of the Moon on the 15th and a similar distance to the southwest of Luna on the 16th.
Moonlight shouldn’t interfere with this year’s display of the annual Leonids meteor shower. Conveniently this display peaks on the night of the 17th/18th, with best viewing times between 2:00 am and morning twilight on the 18th. These meteors are the remnants of particles sputtered off of Periodic Comet Tempel-Tuttle, which has a roughly 33-year orbit. Horace P. Tuttle, one of the co-discoverers, was once an astronomer for the Naval Observatory. It has been responsible for major meteor "storms" seen in 1833, 1866, and especially 1966, when observers in the western U.S. reported seeing dozens of meteors each second! The shower produced several fine displays between 1999 and 2002. In 2000, observing in a park near my home in the DC suburbs, I gave up counting after seeing some 200 shooting stars in half an hour. This year expectations are for a more "normal" display with perhaps 20 or so meteors visible per hour in a dark location, but the shower is notoriously unpredictable in its "off" years, so you may see many more or possibly many fewer. The meteors themselves are very swift, traversing 20 or 30 degrees of the sky in a fleeting instant, with the brighter members leaving persistent smoke trains. The shower radiant is in the "head" of the constellation of Leo, the Lion.
The chill of November nights reminds us that winter is yet to come, and one of the harbingers of the season is the rising of the famous Pleiades star cluster. This small group of stars is now prominent above the eastern horizon by 8:00 pm, and there is perhaps more skylore surrounding this group of stars than any other asterism or constellation. In Greek mythology they were the daughters of Atlas, placed in the sky by Zeus to save them from the amorous overtures of Orion. It is one of the few star patterns mentioned explicitly in The Bible, and the Sisters have been a fixture in western literature since the time of the Romans. They appear in the Native American skylore of the Kiowa nation, who saw them as seven Indian maidens being pursued by giant bears; the Great Spirit saw their plight and pulled them and the ground they were standing on into the sky, thus creating the "Devil’s Tower" formation in Wyoming. The vertical striations on the rock were made by the claws of the bears vainly trying to climb the rock! Even J.R.R. Tolkien incorporated the cluster into the skylore of Middle Earth. Physically the Pleiades comprise a true galactic star cluster consisting of several hundred young stars. About a dozen of the brightest members are theoretically visible to the naked eye, but most of us with average vision can see six or seven. While the cluster is a treat for the unaided eye, they literally sparkle like diamonds in binoculars of low-power telescopes. Give them a look on the next clear, frosty evening.
If you’re out shortly after sunset, see if you can still spot the fading ruddy glimmer of Mars. He gets a visit from the slender crescent Moon on the 15th and 16th, and he doggedly marches eastward into the stars of Sagittarius this week. If you do find him, take a moment to realize that several emissaries from Earth are ether in orbit around him or roving on his dusty surface.
You now don’t need to wait long to see a bright planet in the evening sky. Giant Jupiter rises at around 6:00 pm, following the Seven Sisters into the sky. By late evening he is the most prominent object in the sky, beckoning for a view through the small telescope. Of all the planets, Jupiter offers the best views for virtually any type of optical aid, and the bigger the telescope you observe him with the more detail you will see. Old Jove is a truly gargantuan world, though, which is something no telescope can help you appreciate. His diameter is well over 10 times that of the Earth, which means his volume would swallow up over 1,100 equivalents of our fair world!
You’ll still find dazzling Venus in the pre-dawn sky. This week she closes in on and then passes the bright star Spica in the constellation of Virgo. Venus and Spica are closest on the morning of the 17th. By the end of the week Venus will be closing in on another bright object. That target is Saturn, which is now slowly edging away from the retreating Sun. The planets will be in conjunction next week.