Non-Profit Internet Source for News, Events, History, & Culture of Northern Frederick & Carroll County Md./Southern Adams County Pa.


The Night Sky of September

Dr. Wayne Wooten
Professor of Astronomy

For September 2015, the big event is the total lunar eclipse coming up on the evening of September 27th. I call this one a "School Kids’ Eclipse" because the timing is ideal for the whole family to stay up and watch it. As the full moon rises at sunset, look for the dark shadow of earth to touch the moon’s eastern edge about 8:10 PM CDT, and be completely inside our dark umbra from 9:10 – 10:24 PM. The partial lunar eclipse will end at 11:27 PM locally. 

Moon will be last quarter on September 5th. It will pass 3 degrees north of Venus in the dawn sky on September 10th, then 3 degrees south of Jupiter on the 12th (use binocs to spot them). The new moon on September 13th creates a partial solar eclipse, but seen only in South Africa. The crescent moon the following evening begins Rosh Hashannah, Jewish New Year 5775 AM. On September 15th, the crescent moon passes 5 degrees north of Mercury, low in the SW twilight. The waxing crescent passes 3 degrees north of Saturn on September 19th, and reaches first quarter overhead on September 21st. The Autumnal Equinox occurs at 3:21 AM on September 23rd to begin fall for us. In addition to being eclipsed, the full moon on September 27th is also a "super moon", with the noon near perigee and bigger and brighter than normal! So be sure to capture this rare combination of a super moon in eclipse. Bring your cameras and smartphones to our eclipse watch for great shots!

To the west, Mercury is briefly visible in evening twilight at month’s start. Venus is climbing higher in the dawn sky all month. Mars is close to Venus, but much farther away, smaller, and fainter in the dawn now. Jupiter lies behind the sun as the month starts, and is low in the SE dawn by month’s end. Saturn is still visible in SW twilight, but will be getting lost in sun’s glare by October.

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 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. Saturn 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 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 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! Saturn sits just above the Scorpion’s claws for the rest of the year. 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. Many other clusters and nebulae lie toward the galactic center, and are shown on the SkyMap chart and discussed on its binocular and telescope object listing on page 2.

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"…a fine sight under steady sky conditions

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. They will also reveal the easiest planetary nebula to see, M-27 in Vulpecula, just south of Alberio.

Read past issues of the Sky at Night