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The Sky This Week, 2015 August 25 - September 1

A Fishy Full Moon

The Sturgeon Moon, 2008 August 17

rising over Wilderness Point, Fishers Island, New York

The Moon brightens the evening sky this week, moving from the star-clouds of the Sagittarius Milky Way into the sparsely populated starfields of the autumn constellations. Full Moon occurs on the 29th at 2:35 pm Eastern Daylight Time. August’s Full Moon is popularly known as the Corn Moon, Grain Moon, or Sturgeon Moon. If you like corn-on-the-cob or caviar, this Moon’s for you!

Bright moonlight washes out the more subtle details of the late summer sky, but some of the season’s brighter stars and star patterns are at their best despite the Moon’s best efforts. By 9:00 pm the sky should be dark enough to find Scorpius, led by the ruddy star Antares, just west of the meridian in the southern sky. The constellation has an interloper this year in Saturn, whose bright yellow gleam mingles with the stars that form the Scorpion’s "head". To me the constellation’s most striking feature is the Scorpion’s "tail", which resembles a large fish hook dragging the southern horizon. Two bright stars, known to some Native Americans as the "swimming ducks", mark the stinger of the Scorpion and indicate the rough direction of the center of the Milky Way galaxy. Scorpius is one of the few constellations that resemble its namesake, and is an especially striking sight when viewed over an ocean horizon.

High overhead by the late evening you’ll find the Summer Triangle, made up of the bright stars Vega, Deneb, and Altair. Vega, the brightest, leads the small constellation of Lyra, the Harp, which consists of a small parallelogram of second- and third-magnitude stars. Altair, the southernmost of the triangle, leads Aquila, the Eagle, a rather indistinct constellation embedded in the Milky Way. Deneb marks the tail of Cygnus, the Swan, a large group that is sometimes called the Northern Cross. The "head" of the Swan (or the base of the cross) is a third-magnitude star called Albireo, located almost exactly in the middle of the triangle. Albireo is a treat for anyone with a small telescope; what appears as a single star with the unaided eye is easily resolved into a beautifully colored double star of blue and gold components.

Before we left on vacation in early August we still had Venus and Jupiter to look for in the evening twilight sky. Venus passed conjunction with the Sun in the 15th and is rapidly emerging in the east before dawn. Jupiter passes behind the Sun on the 26th and will gradually emerge into the morning sky in mid-September.

This leaves Saturn as the sole naked-eye planet visible in the evening sky. As mentioned earlier the ringed planet is located near the "head" of Scorpius and is well-placed for viewing about half an hour after sunset until around 10:30 pm, when he begins to wallow in the turbulence and haze above the southwest horizon. Almost any telescope will show the planet’s distinctive rings, which are now tipped generously in our direction.

This week marks the 180th anniversary of the "Great Moon Hoax", a series of articles that were printed in the "New York Sun" newspaper purporting to describe the discovery of living beings on the Moon by Sir John Herschel, one of the world’s most prominent astronomers of the time. The article was a total fabrication, but it established the Sun as one of New York’s most popular papers for decades to come.


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