In the Sky This Month

Andromeda, the princess, is in the east and northeast as the sky gets good and dark on September nights. It’s not especially bright, but you can find it by looking to the lower left of the more prominent Great Square of Pegasus.

The Moon is at last quarter at 1:25 a.m. CDT tomorrow, as the Sun illuminates half of the lunar hemisphere that faces us. This phase is known as last quarter because the Moon is three-quarters of the way through its month-long cycle of phases.

Aldebaran, the brightest star of Taurus, perches close to the Moon as they climb into view around midnight, and especially close at first light tomorrow. As seen from parts of the western U.S., the Moon will pass in front of Aldebaran, blocking its light.

This is a great time of year to watch the Milky Way, the glowing band of stars that outlines the disk of our home galaxy. The Milky Way arcs high overhead around 9 or 10 p.m., before the Moon rises. You need dark skies to see it.

The brightest star of Pegasus, the flying horse, is Enif, from an Arabic name that means “the horse’s nose.” It’s to the upper right of the Great Square of Pegasus, which is in the east in early evening.

The 13th constellation of the zodiac rolls across the sky this evening. Ophiuchus is in the southwest at nightfall and begins to set after midnight. It covers such a huge area that it takes several hours for the whole thing to drop below the horizon.

The just-past-full Moon lights up the sky tonight. Since we’re getting close to the autumnal equinox, the Moon mimics the Sun and rises almost due east. It arcs high across the south later on.

Astronomers will be keeping an eye on a star near Orion’s Belt this month. The three-star belt is in the southeast at dawn, pointing up and down. If the star gets fainter, it could mean that a planet with a giant set of rings orbits the star.

The Moon is full tonight. Most years, September’s full Moon is the Harvest Moon. This year, though, October’s full Moon is closer to the autumnal equinox, so it takes the title. September’s full Moon is the Fruit Moon or Corn Moon.

Vega, one of the brightest stars in the night sky, passes high overhead this evening. From the middle latitudes of the United States, in fact, it passes directly overhead, which is the point in the sky called the zenith.