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For the month of September

Summer Sky Map © Wil Tirion

September Constellations

At nine pm on September evenings, the Big Dipper, an asterism, or star shape, within the constellation Ursa Major (the Great Bear), is quite low in the north. The bowl of the Little Dipper, in Ursa Minor, the Little Bear, is upside down above it. Trace the Little Dipper's handle to its tip to locate Polaris, the North Star. It marks the northern pole of the celestial sphere and is the extension of Earth's North Pole into space.

The Big Dipper's handle arcs toward Arcturus, the big orange alpha (or brightest) star in the constellation Bootes, the Herdsman, just setting on the northwestern horizon. Look for the pretty half-circle of Corona Borealis, the Northern Crown, almost due west, above Arcturus and just to the left of Bootes. Above Corona Borealis is Hercules and, higher still, Vega, the constellation Lyra's bright blue-white alpha star. Vega marks one corner of the Summer Triangle, made up of three bright stars from three different constellations. Another corner, Deneb, the alpha star in Cygnus, the Swan, is almost directly overhead.

In the northeastern quadrant of the sky, Andromeda, the Princess, stretches her way toward the horizon from the northeastern star of the Great Square of Pegasus, the Winged Horse. Perseus, the Hero, who saved Andromeda from Cetus, the Sea Monster, lies below her and to the left. On a very dark, clear night you might be able to make out a fuzzy patch of light above the middle of the two lines of stars that form Andromeda; this is the Great Andromeda Galaxy, the most distant object the eye (unaided by binoculars or a telescope) can see. Andromeda's mother, Queen Cassiopeia, above and to her left, now looks like a number 3, while her father, King Cepheus, is high in the northern sky. Just rising in the northeast is Capella, the alpha star in the constellation Auriga, the Charioteer. Capella is the sixth brightest star in the sky and has long been important in navigation.

Look due south to see Capricornus and Delphinus at their most visible. Capricornus, a rather faint assemblage of stars, represents an odd creature called the Sea Goat, while Delphinus appears as a charming little dolphin arcing over the waves. The southern portion of the sky is occupied by many constellations associated with water. In addition to the two aforementioned, Piscis Austrinus, the Southern Fish, and Aquarius, the Water Bearer, can be found here. Farther around to the east are Cetus, the Sea Monster, and Pisces, the Fish. The only bright star in the southeast is Fomalhaut, the alpha star in Piscis Austrinus, close to the horizon.

Halfway up the southwestern part of the sky is Altair, the alpha star in the constellation Aquila, the Eagle. It marks the third corner of the Summer Triangle. The brightest corner, Vega, is in the west. Full darkness brings the full glory of the Milky Way, arching across the sky from the south to the northeast, passing right behind the Summer Triangle. Scan its glowing star clouds with binoculars or a telescope to see star clusters and nebulas by the dozens. Sagittarius, lying toward our galaxy's center, is low in the southwestern sky; it will soon set, not to be seen again until late next spring.