The Night Sky of September

Dr. Wayne Wooten
Professor of Astronomy

For September the moon will be first quarter on September 2nd, just to the west of Jupiter. Two days later the waxing gibbous moon is just west of Saturn. The full moon, the Harvest Moon, is on September 14th. The Autumnal Equinox begins fall at 2:50 AM CDT on September 23rd. The last quarter moon is on September 21st, and the new moon on September 28th.

While the naked eye, dark adapted by several minutes away from any bright lights, is a wonderful instrument to stare up into deep space, far beyond our own Milky Way, binoculars are better for spotting specific deep sky objects. For a detailed map of northern hemisphere skies, about August 31st visit the www.skymaps.com website and download the map for September 2019; it will have a more extensive calendar, and list of best objects for the naked eyes, binoculars, and scopes on the back of the map. Another aid is the wonderful video exploring the September 2019 sky, featuring many different objects, available from the Hubble Space Telescope website at: http://hubblesite.org/explore_astronomy/tonights_sky/. Sky & Telescope has highlights at www.skyandtelescope.com/observing/astronomy-podcasts/ for observing the sky each week of the month.

Mercury, Venus, and Mars are all still too close to the Sun for easy observing. Jupiter is visible in SW evening twilight, but getting lower each evening in Ophiuchus. At dusk, Saturn lies due south, just east of the teapot of Sagittarius, and its 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. Jupiter is just NW of Spica, a little brighter and more yellow in color. 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. Our featured photo is of this stellar nursery.

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 Alberio, 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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