The stars of autumn begin to push those of summer out of the way as the nights grow longer and cooler. Pegasus is in view in the east as night falls, with several related constellations following the flying horse into the sky over the next few hours.
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In the Sky This Month
September 26: Sending a Message
Pegasus, the flying horse, is climbing across the night sky. It’s in the east as night falls. It’s preceded by Equuleus, the little horse, to the upper right of Pegasus. Equuleus is the smallest of all the constellations passed down from the ancient world.
September 27: Mirach
The binary system known as Mirach forms the second-brightest star in the constellation Andromeda, which is in the east and northeast as night falls. The system’s main star is almost 100 times wider than the Sun and 2,000 times brighter.
September 28: Last-Quarter Moon
The Moon is at last quarter tonight, as it lines up at a right angle to the line between Earth and the Sun. Sunlight illuminates the western half of the lunar hemisphere that faces our planet.
September 29: Draco
Draco, the dragon, is in the north and northwest at nightfall. It wraps around the North Star, Polaris. The constellation’s brightest star, Eltanin, which is almost as bright as Polaris, is high overhead, at the top of the dragon’s twisting path of faint stars.
September 30: Thuban
Today, Earth’s north pole aims at Polaris. But thousands of years ago it aimed at a star in the tail of Draco, the dragon. Thuban served as the North Star when the pyramids of Giza were being built, so architects used it to align the sides of the pyramids.
October 1: Early Winter
Autumn is barely under way, but you can get a preview of the winter sky this week in the hours before dawn. Taurus, the bull, passes high overhead. Orion stands in the southeast, with Sirius, the sky’s brightest star, low in the south-southeast.
October 2: Moon and Regulus
Regulus, the heart of the lion, perches to the right of the Moon at dawn tomorrow. The star is several times bigger and heavier than the Sun and hundreds of times brighter. It is shaped like a round jelly doughnut, a third wider through the equator than the poles.
New September 6, 7:52 pm
First September 13, 3:39 pm
Full September 20, 6:55 pm
Last September 28, 8:57 pm
Times are U.S. Central Time.
Perigee September 11
Apogee September 26
The full Moon of September is the Fruit Moon or Green Corn Moon. This year it’s also the Harvest Moon.