A traffic jam highlights the morning sky this month, as three planets line up near Regulus, the heart of Leo. The planets move through different configurations during the month, providing a different view each day. In the evening sky, some of the signature constellations of summer begin dropping from view, while some of the faint constellations of autumn climb skyward in the east and southeast.
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In the Sky This Month
September 26: Moon and Saturn
A pair of bright objects stands in the southwest this evening: the Moon and the planet Saturn. Saturn, the solar system’s second-largest planet, perches below the Moon, and looks like a bright star.
September 27: First-Quarter Moon
The Moon is at first quarter tonight. Sunlight illuminates exactly one-half of the lunar hemisphere that faces Earth. The sunlit portion of the Moon will continue to grow until the Moon is full on October 5, the date of the Harvest Moon.
September 28: Eagles
Several eagles soar across the sky tonight. The brightest is the star Vega, the swooping eagle, which is overhead at nightfall. Altair, the flying eagle, is in the southeast. The Eagle Nebula is a cloud of gas and dust that outlines a bird of prey with open wings.
September 29: Summer Triangle
Summer officially ended a week ago, but one of its most visible star patterns is still high overhead in the evening. The Summer Triangle consists of the bright stars Deneb, Vega, and Altair. The triangle is directly overhead about 8 p.m.
September 30: Double Double
Epsilon Lyrae stands quite close to Vega, one of the brightest stars in summer and autumn skies, which is high in the west at nightfall. Epsilon Lyrae consists of two pairs of stars. Each pair is tightly bound, with the two pairs quite far apart.
October 1: Early Winter
Autumn is just underway, but you can get a preview of the winter sky in the hours before dawn. Taurus, the bull, is high overhead. Orion is due south, with Sirius, the sky’s brightest star, in the south-southeast.
October 2: Aquarius
The celestial water bearer pours a streamer of faint stars across the southern sky on October nights. Aquarius is low in the southeast as the sky gets good and dark tonight, surrounding the gibbous Moon, and stands due south before midnight.