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The Sky This Week, 2017 November 14 - 21

The Seven Sisters on the rise
M45_161231_02small.jpg
Messier 45, the Pleiades Star Cluster
imaged 2016 December 31 from Mollusk, VA by Geoff Chester
with an Explore Scientific AR102 4-inch f/6.5 refractor
and Canon EOS Rebel T2i DSLR.

The Moon spends most of the week in the glow of morning and evening twilight. New Moon occurs on the 18th at 6:42 am Eastern Standard Time. Luna may be found as a waning crescent in the company of the planets Mars, Jupiter, and Venus in the pre-dawn hours of the 15th, 16th, and 17th. She returns to the evening sky by the evening of the 20th, when you’ll find her low in the southwest as evening twilight fades.

The sky in the middle of November is one of transition between the setting stars of summer and the rising stars of winter. On the whole there aren’t that many bright stars above the horizon during the mid-evening hours. The solitary first-magnitude star among the autumnal constellations crosses the meridian at around 7:30 pm, low in the southern reaches of the sky. This solitary star is Fomalhaut, the brightest and only prominent star in the obscure constellation of Pisces Austrinus, the Southern Fish. It is one of the closer stars to the Sun at a distance of about 23 light years, but somehow its isolated place in the sky makes it seem much more remote. Fomalhaut transits the meridian just before the westernmost stars in the Great Square of Pegasus, the "signature" constellation of the seasonal sky.

High in the east during the later evening hours is a small knot of stars that have probably garnered more attention in skylore that the rest of the constellations combined. Urban skywatchers can see the group as a small fuzzy grouping on clear nights, and as you move farther from the middle of the city the group begins to come into better focus under darker skies. Viewers in the suburbs should be able to see around half a dozen stars in a pattern that resembles a small measuring spoon, while those graces with dark country skies can easily seven or more stars. The group goes by as many names as there are colloquial legends of the sky, and we call the group The Pleiades or The Seven Sisters. In Greek mythology they were the daughters of Atlas and half-sisters of the nearby Hyades, which surround the bright star Aldebaran. Since very ancient times the risings and settings of the Pleiades have dictated agricultural activities, and in the Mediterranean region they were seen as harbingers of stormy weather that comes with the arrival of winter. The vast pre-Columbian city of Teotihaucan, which was 1000 years old when the Aztecs ruled Mexico, has all of its major streets and its largest temple, the so-called "Pyramid of the Sun", laid out in alignment with the setting of the Seven Sisters. The stars have even found their way into the mythology of J.R.R. Tolkien’s Middle Earth, where Hobbits, Elves, and Men knew them as Remmirath, "the Netted Stars". The group is a true star cluster, one of the closest to the Earth, about 440 light-years away. Keen-eyed observers under very dark skies may be able to see up to a dozen of its components, while binoculars will reveal several dozen. Astronomers have counted about a thousand total cluster members. The brightest members are energetic young blue stars that have luminosities that are thousands of times that of the Sun.

Try to catch a last glimpse of Saturn in twilight on the evening of the 20th. On that night the slender waxing crescent Moon will be located about two degrees north of the ringed plane. Both objects will be low in the southeastern sky, and you’ll probably need binoculars to see Saturn in the relatively bright sky.

Mars may be found about five degrees above the waning crescent Moon before dawn on the 15th. He’s also fairly close to the bright star Spica, but you should be able to distinguish him by his ruddy tint, which contrasts nicely with the ice-blue of the star.

Venus starts the week close to Jupiter, and as the week passes the dazzling planet leaves Old Jove in her wake. Look for the pair in bright twilight, low in the east about half an hour before sunrise.

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