In the Sky This Month

For much of the country, September is a perfect time for some evening skywatching. The nights are longer and cooler but not yet frigid, and there’s plenty to look at. The Summer Triangle remains in good view high in the sky, while Scorpius and Sagittarius wheel across the southwest. In the east, Pegasus, Andromeda, and Perseus climb into view after sunset.

September 21: Autumn

Fall arrives in the northern hemisphere this weekend. It’s the autumnal equinox, which is the point at which the Sun crosses the equator from north to south. It occurs at 8:54 p.m. CDT Saturday.

September 22: Fomalhaut System

Fomalhaut, the leading light of Piscis Austrinus, the southern fish, is quite bright. It rises to the lower right of the Moon tonight, and stands below the Moon around midnight. It’s in a fairly barren region of sky, which makes it easier to pick out.

September 23: Harvest Moon

The Harvest Moon lights up the sky the next few nights. It’s the full Moon closest to the fall equinox, which was yesterday. The Moon will be full at 9:52 p.m. CDT tomorrow night. But it will look almost the same on the nights before and after that.

September 24: Moon in the Sea

The Moon is swimming through the Celestial Sea, a group of constellations with a watery theme. Tonight, the Moon is near the border between Aquarius, the water bearer; Pisces, the fishes; and Cetus, the whale or sea monster.

September 25: Arcturus

Look in the west as twilight fades this evening for one of the most commanding stars in the sky: Arcturus, in the constellation Bootes, the herdsman. It shines pale yellow-orange.

September 26: Chasing Dogs

Two “dog stars” chase across autumn’s pre-dawn sky. The brighter one is Sirius, in Canis Major, the big dog. The other is Procyon of Canis Minor, the little dog. Both are high in the sky at first light, with Procyon far to the upper left of Sirius.

September 27: Triangulum

Wedged into a cozy space between the well-known constellations Andromeda, Aries, and Perseus is tiny Triangulum, the triangle. Its three brightest stars form a long, thin wedge. It rises in the northeast in early evening.