A new season opens up in the evening sky. Pegasus slides into view in the east shortly after night falls, marked by the Great Square, while the constellations of the “celestial sea”—Capricornus, Aquarius, Pisces, and others—flow across the south.
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In the Sky This Month
September 25: New Moon
The Moon is new today as it crosses the imaginary line between Earth and the Sun. It is lost from view in the Sun’s glare but will climb into view as a thin crescent quite low in the west shortly after sunset on Tuesday.
September 26: Big Story
Five constellations that form part of the same story spread across the evening sky. Andromeda, Cassiopeia, Cepheus, Cetus, and Perseus all climb up the eastern side of the sky, telling a story of vanity, sacrifice, and heroism.
September 27: Earthshine
The Moon is in its waxing crescent phase, so sunlight illuminates only a sliver of the lunar disk. As night falls, the dark portion of the disk becomes visible because it is illuminated by earthshine, or sunlight reflected off of Earth.
September 28: Zubenelgenubi
The southern claw of the scorpion stands close above the Moon as darkness falls tonight. Formally, the star belongs to Libra, the balance scales. In ancient times, though, it represented one of the claws of Scorpius, which is to the left of Libra.
September 29: Thuban
Draco, the dragon, slithers around the Little Dipper. Its brightest star is Thuban, between Kochab, which is in the dipper, and Mizar, in the handle of the Big Dipper. Earth’s north pole pointed at Thuban 4,800 years ago, making it the pole star.
September 30: Moon and the Scorpion
Some of the bright stars of the scorpion line up near the Moon tonight. The brightest star, Antares, is quite close to the Moon. Acrab, in the scorpion’s head, is farther to the right of the Moon. Both stars are fated to blast themselves to bits as supernovae.
October 1: Disappearing Scorpius
Two of the constellations of summer bookend the Moon tonight. Sagittarius is to the left of the Moon at nightfall. Some of its bright stars form the shape of a teapot, with the Moon near the tip of the spout. Scorpius curls below and to the right of the Moon.
First September 3, 1:08 pm
Full September 10, 4:59 am
Last September 17, 4:52 pm
New September 25, 4:55 pm
Times are U.S. Central Time.
Perigee September 7
Apogee September 19
The full Moon of September is the Fruit Moon or Green Corn Moon. This year it’s also the Harvest Moon.