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Hal Kibbey

Last modified: Tuesday, September 1, 2009


Jupiter rules the night sky in September

Sept. 1, 2009

BLOOMINGTON, Ind. -- Jupiter, the solar system's largest planet, will dominate the night sky during September. Glowing low in the southeast as evening twilight fades, Jupiter will climb high in the south before midnight and set around the time morning twilight begins. With no bright stars nearby, the planet will be easy to spot in the constellation Capricornus the Goat.


Jupiter's four brightest moons were discovered by Galileo, and they can usually be seen with binoculars. But for about two hours on the night of Sept. 2-3, all four moons will be hidden either in front of the planet, behind it or in its shadow. Jupiter will not appear "moonless" again until 2019.

Mars will rise around midnight among the stars of the constellation Gemini the Twins. The "twin" stars are Castor and Pollux, and red-orange Mars will join them to form a trio that will be halfway up the southeastern sky by the start of morning twilight. Mars will change its position relative to the stars as the month advances.

Venus will be a brilliant "morning star" during September, rising in the east-northeast about three hours before the sun at the beginning of the month and an hour later by month's end. On Sept. 1 and 2, Venus will be just south of the Beehive star cluster in the constellation Cancer the Crab. The best time to look will be around 5 a.m. local daylight time, when binoculars will show the cluster before twilight starts to brighten the sky. Venus will be easy to identify, outshining everything else. On Sept. 20 an hour before sunrise, Venus will be very close to the bright star Regulus in the constellation Leo the Lion.

Near the end of the month, Mercury will become visible very low in the east before dawn. On Sept. 30, the white pinpoint of light will glimmer through the twilight a half hour before sunrise, below and slightly to the left of Venus.

Saturn will be too close to the sun to be seen during September.

International Space Station

The International Space Station can be seen from time to time as it crosses the sky, if you know when and where to look. Information on how to locate it is provided at


On a clear September night, you may be lucky enough to see an aurora (sometimes called "northern lights"). These silent ribbons and curtains of light can appear whenever the sun is active, but they are especially likely from August to October. Eruptions from the sun's surface hurl enormous amounts of charged particles into space, and when some of these solar particles head in our direction, they cause auroral activity. For details and photographs, see You can watch for auroras when they are most likely to happen by checking Web sites such as and Sightings of auroras are reported at


The sun will reach the September equinox on Sept. 22 at 5:19 p.m. EDT (21:19 Universal Time), marking the start of fall in the Northern Hemisphere and spring in the Southern Hemisphere. For the next six months in the Northern Hemisphere, the nights will be longer than the days.

Moon phases

The moon will be full on Sept. 4, at third quarter on Sept. 11, new on Sept. 18 and at first quarter on Sept. 26.