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Hal Kibbey

Last modified: Thursday, September 2, 2010


Jupiter rules the night sky in September

Sept. 2, 2010

BLOOMINGTON, Ind. -- Jupiter, the solar system's largest planet, will dominate the sky nearly all night during September, presenting its best appearance in almost 50 years. Glowing low in the east as evening twilight fades, Jupiter will climb high in the south before midnight and set in the west around the time morning twilight begins.

With no bright stars nearby, the planet will be easy to spot. Jupiter's four brightest moons were discovered by Galileo, and they can usually be seen with binoculars. All four of these moons will be grouped to the east of Jupiter before the morning sky brightens on Sept. 24.


Photo courtesy of NASA


Print-Quality Photo

Venus and Mars will form a tight trio with the bright white star Spica low in the west-southwest at the beginning of the month. Brilliant white Venus on the left (south) will be 300 times brighter than pale orange Mars on the right, which will be hard to see without binoculars in the bright glow of twilight. The two planets will remain close all month as Spica gradually moves away from them toward the right (west).

As the evening sky darkens early in the month, Saturn will be visible with binoculars very low in the west, far to the right of Venus. By mid-month Saturn will be too close to the sun to be seen, and it will pass through conjunction with the sun on Sept. 30.

In the last two weeks of the month, Mercury will become visible very low in the east-northeast about a half hour before sunrise. Look for the white pinpoint of light glimmering through the morning twilight just below the bright white star Regulus in the constellation Leo the Lion. This will be Mercury's best morning appearance of the year for observers at mid-northern latitudes.

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 11:09 p.m. EDT (Sept.23 at 3:09 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 at third quarter on Sept. 1, new on Sept. 8, at first quarter on Sept. 15 and full (the Harvest Moon) on Sept. 23.