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The Night Sky of September

Dr. Wayne Wooten
Professor of Astronomy

(9/2021) For September, the moon is waning crescent in the first week, reaching new on September 6th. The waxing crescent lies to the upper right of Venus in evening sky on September 9th. It is first quarter on September 13th. The waxing gibbous moon passes below Saturn on September 16, then below brighter Jupiter on September 17th. The full Harvest Moon is on September 20th. The Autumnal Equinox begins fall on September 22nd at 1:21 p.m. The moon is last quarter on September 28th.

Fall gives us our best meteor showers. Around October 20th, Halley’s Comet debris strikes us with the Orionid Meteor Shower, and about November 17th, the Leonid Meteor shower peaks. Then about December 14th, we get the Geminid display, usually the best of the year. Dani was lucky to catch this meteor is the evening sky; most appear after midnight, when our side of the planet faces the debris streams head on.

Mercury is out of view, too close to the Sun in September. Venus dominates the evening sky in the SW, passing just above Spica on September 5th. Mars too lies behind the Sun this month. Jupiter and Saturn put on a fine show in the SE at sunset. Jupiter features its four Galilean moons in small scopes, all in a row around its equator, and its Great Red Spot is still active. At dusk, fainter Saturn lies due south, just west of Jupiter, and rings are tilted widely open for great telescopic views now. Its large and fascinating moon Titan is also easily need in small scopes.

From the Dipper’s handle, we ‘arc’ SE to bright orange Arcturus, the brightest star of Spring. Spike south to Spica, the hot blue star in Virgo. Brilliant Venus passes above Spica on September 5th. Note that Spica is now low in the SW, and by September’s end, will be lost in the Sun’s 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 Hades…a honeymoon in hell…really, 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 (aren’t 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 Noah’s 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 even our own civilization.

To the south, Antares marks the heart of Scorpius. It appears reddish (its Greek name means rival of Ares or Mars to the Romans) 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 Saturn’s orbit! Near the tail of the Scorpion are two fine open clusters, faintly visible to the naked eye, and spectacular in binoculars. The clusters lie to the upper left of the bright double star that marks the stinger in the Scorpion’s tail. The brighter, M-7, is also known as Ptolemy’s Cluster, since he included it in his star catalog about 200 AD.

East of the Scorpion’s 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 teapot’s spout is the fine Lagoon Nebula, M-8, easily visible with the naked eye. Like the clusters, it shows up well in Dani’s smartphone shot…the things these new gadgets can do!

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". This is fine sight under steady seeing conditions over 150X with scopes 4" or larger. Between the two bottom stars; the Ring Nebula, marked "M-57" on the Skymap, is a smoke ring of gas and dust expelled by a dying red giant star while its core collapsed to a white dwarf. A similar fate is expected for our own sun in perhaps five billion more years.

To the northeast of Vega is Deneb, the brightest star of Cygnus the Swan. At the other end of the "northern Cross" that makes up the body of Cygnus is Albireo, the finest and most colorful double star in the sky. Its orange and blue members are well resolved at 20X by any small scope. 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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