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

 

The Night Sky of August

Dr. Wayne Wooten
Professor of Astronomy

For August 2015, the last quarter moon is on August 7th. The new moon is on August 14th, and will not interfer with the peak of the Perseid meteor shower on the mornings of August 12-13th this year. From a dark observing site, you can expect about a meteor a minute from 11 PM until dawn, with the radiant, Perseus, rising in the NE about 11 PM. The waxing crescent moon passes 2 degrees south of Mercury in twilight on August 16th. The moon is first quarter on August 22nd, and passes 2.6 degrees north of Saturn, the only planet out in the evening sky now. The full moon, the Green Corn moon, occurs on August 29th.


North American Nebula

Mercury is low in the western evening sky at midmonth, with the crescent moon south of it on the 16th. Venus and Jupiter are both lost in sunís glare, with Venus passing between us and Sun on August 15th, and Jupiter behind the Sun on August 26th. Mars is also hard to observe, in the dawn sky rising about an hour before the sun. Only Saturn is easy to observe; Saturn lies just west of the claws of Scorpius in the southern evening sky. Enjoy the rings, now 24 degrees open and tilted toward earth and sun; the most beautiful planet falls closer to the western horizon each evening, to be lost in the sunís glare in 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.

Taking the arc in the Dipperís handle, we "arc" SE to bright orange Arcturus, the brightest star of Spring. Cooler than our yellow Sun, and much poorer in heavy elements, some believe its strange motion reveals it to be an invading star from another smaller galaxy, now colliding with the Milky Way in Sagittarius in the summer sky. Moving almost perpendicular to the plane of our Milky Way, Arcturus was the first star in the sky where its proper motion across the historic sky was noted, by Edmund Halley.

Spike south to Spica, the hot blue star in Virgo. From Spica curve to Corvus the Crow, a four-sided grouping. It is above Corvus, in the arms of Virgo, where our large scopes will show members of the Virgo Supercluster, a swarm of over a thousand galaxies about 50 million light years away from us.

Hercules is overhead, with the nice globular cluster M-13 marked on your sky map and visible in binocs. It is faintly visible with the naked eye under dark sky conditions.

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.

Below Vega are the two bright stars of the Summer Triangle; Deneb is at the top of the Northern Cross, known as Cygnus the Swan to the Romans. It is one of the most luminous stars in our Galaxy, about 50,000 times brighter than our Sun. To the south is Altair, the brightest star of Aquila the Eagle. If you scan the Milky Way with binocs or a small spotting scope between Altair and Deneb, you will find many nice open star clusters and also a lot of dark nebulae, the dust clouds from which new stars will be born in the future. One of the most famous is the "North American Nebula", in the same binocular field as Deneb. The North American lies to the lower left of bright blue Deneb, with still more nebulae and dust clouds along the Milky Way here.

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! Just above the tail of the Scorpion are two fine naked eye star clusters, M-7 (discovered by Ptolemy and included in his catalog about 200 AD) and M-6, making one of the best binocular views in the sky. Your binoculars are ideally suited to reveal many fine open star clusters and nebulae in this region of our Galaxy.

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. In the same binocular field just north of the Lagoon is M-20, the Trifid Nebula. Just east of the pair is the fine globular cluster M-22, faintly visible to the naked eye and spectacularly resolved in scopes of 8" or larger aperture.

Read past issues of the Sky at Night