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The Night Sky of September

Dr. Wayne Wooten
Professor of Astronomy

For September 2012, the Moon will be last quarter on September 8th, with the full moon occurring on August 31st; it will be passing just south of Jupiter that morning, with Jupiter being occulted for viewers in central and south America. The waning crescent moon passes 3.6 degrees south of Venus in the dawn on September 12th, and the new moon occurs on September 16th. The crescent moon following it marks Rosh Hashanah, the Jewish New Year for 5773 AM. The waxing crescent moon passes 5 degrees south of Saturn on September 18th, then .8 degrees south of Red Mars on September 19th. The Fall Equinox occurs at 9:47 AM CDT on September 22nd, the same day as the first quarter moon. The Full Moon, the Harvest Moon, occurs on September 30th.

To the west, we are losing Saturn into the sunís glare, and Mars moves rapidly eastward from Virgo into Libra this month. Far from the earth currently, it is getting fainter, and too will be lost in sunís glare by yearís end. Jupiter dominates the late evening skies during the autumn of 2012. He reaches opposition on December 3rd, among the stars that make up the head of Taurus. Venus dominates the dawn, but is now heading back toward the sun, to pass behind it in early 2013.

The Big Dipper rides high in the NW at sunset, but falls lower each evening. Good scouts know to take its leading pointers north to Polaris, the famed Pole Star. For us, it sits 30 degrees (our latitude) high in the north, while the rotating earth beneath makes all the other celestial bodies spin around it from east to west. It is this time of year at an American Indian legend tells of the Bear and three hunters. The bowl is the bear, the three handle stars of the dipper the hunters. The first carries a bow, and has shot the bear in its flanks. The second optimistically carries a bowl on his shoulder for bear stew; look closely, and you can see the pot (Mizar. horse in Arabic, and Alcor its rider more traditionally). The last hunter carries firewood for the feast. The wound is minor, and the bear has not lost a step, but in the fall, as the bear goes into hiding along the NW horizon, the wound opens slightly, and blood oozes out to fall on the tree leaves and paint them red this time of year.

From the Dipperís handle, we "arc" SE to bright orange Arcturus, the brightest star of Spring. Spike south to Spica, the hot blue star in Virgo. Saturn is just NW of Spica, a little brighter and more yellow in color. Note that Spica and Saturn are both now low in the SW, and by Septemberís end, will be lost in the Sunís glare due to our annual revolution of the Sun making it appear to move one degree per day eastward. To the Greeks, Spica and Virgo were associated with Persephone, the daughter of Ceres, goddess of the harvest. In their version of "Judge Judy", the beautiful young daughter falls for the gruff, dark god of the underworld, Pluto. He elopes with her, much to the disapproval of mother Ceres, and they marry in his underworld kingdom of HadesÖa honeymoon in hellÖreally, he does love her as well, and the marriage itself works well. But it is the reaction of Ceres that creates alarm. Very despondent over the loss of her young daughter to a fate as bad as death, Ceres abandons the crops, which wither. Soon famine sets in, and humanity appeals to Jupiter to save us all. Calling all together, Jupiter hears that Ceres wants the marriage annulled, Persephone loves them both, and Pluto wants his mother in law to stop meddling. Solomon style, Jupiter decides to split her up, not literally, but in terms of time. In the compromise (arenít all marriages so?), when you can see Spica rising in the east in March, it means to plant your peas. For the next six months, she visits upstairs with as very happy mama, and the crops will prosper. But now, as Spica heads west (to the kingdom of death, in most ancient legends) for six months of conjugal bliss with Pluto, it is time to get your corn in the crib. This simple story, told in some form for as long as Noahís flood, was one of the ways our ancestors 7,000 years ago knew the solar calendar and when to plant and harvest. As you watch Spica fade, thank this star for agriculture, and in a certain sense, even our own culture.

To the south, Antares rises about the same time in Scorpius. It appears reddish (its Greek name means rival of Ares or Mars to the Latins) because it is half as hot as our yellow Sun; it is bright because it is a bloated red supergiant, big enough to swallow up our solar system all the way out to Saturnís orbit! Near the tail of the Scorpion are two fine open clusters, faintly visible to the naked eye, and spectacular in binoculars. This photo of Scorpius and Sagittarius. The clusters lie to the upper left of the bright double star that marks the stinger in the Scorpionís tail. The brighter, M-7, is also known as Ptolemyís Cluster, since he included it in his star catalog about 200 AD.

East of the Scorpionís tail is the teapot shape of Sagittarius, which marks the heart of our Milky Way galaxy. Looking like a cloud of steam coming out of the teapotís spout is the fine Lagoon Nebula, M-8, easily visible with the naked eye.

The brightest star of the northern hemisphere, Vega dominates the NE sky. Binoculars reveal the small star just to the NE of Vega, epsilon Lyrae, as a nice double. Larger telescopes at 150X reveal each of this pair is another close double, hence its nickname, the "double double"Öa fine sight under steady sky conditions. At the bottom of the parallelogram that marks the body of the lyre lies the beautiful Ring Nebula, M-57. It lies midway between the two southernmost stars, is visible in binoculars, and even in small telescopes appears as a ghostly smoke ring. The colors show up well in photos, but not visually. Planetary nebulae are named for their often circular shape, like the disk of distant planets; in reality, they are shells of glowing gas, ionized by the ultraviolet radiation of the now revealed core of a red giant star in the final stages of its collapse.

To the northeast of Vega is Deneb, the brightest star of Cygnus the Swan. To the south is Altair, the brightest star of Aquila the Eagle, the third member of the three bright stars that make the Summer Triangle so obvious in the NE these clear September evenings. Binoculars should be taken to the deep sky gazes to sweep the rich portion of the Galaxy now best placed overhead in this area.

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