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In the Sky This Month

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.

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.

October 2: Almach

Almach, one of the brightest stars of the constellation Andromeda, is in the northeast as night falls and passes high overhead in the wee hours of the morning. A telescope reveals two stars, one of which is yellow orange, the other blue.

October 3: Watery Moon

The Moon is moving from one water constellation, Aquarius, to another, Capricornus. Many lunar features are associated with water, too. The dark patches that form the “man in the Moon” are known as seas or oceans. They are made of volcanic rock, not water.

First QuarterFirst September 3, 1:08 pm

Full MoonFull September 10, 4:59 am

Last quarterLast September 17, 4:52 pm

New MoonNew 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.