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Hal Kibbey

Last modified: Friday, November 30, 2012



Nov. 29, 2012

BLOOMINGTON, Ind. -- Jupiter will reach its annual peak in December, appearing in the east during evening twilight and dominating the sky all night. The giant planet will be at opposition on Dec. 2, rising above the eastern horizon soon after sunset.


Photo courtesy of NASA


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Viewed from mid-northern latitudes, it will be about 70 degrees above the southern horizon around local midnight, minimizing the amount of Earth's atmosphere that the planet's light must pass through to reach a telescope on the ground. Jupiter's four planet-sized moons -- Io, Europa, Ganymede and Callisto -- will be on vivid display when Jupiter is so high in the sky.

Mars will continue to be low in the southwest after sunset during December, appearing about 10 degrees above the horizon as the evening sky darkens. The red-orange object will be easy to see if you have an unobstructed view, moving eastward quickly and so remaining at about the same altitude every night. Mars will set about two hours after the sun all month.

As Jupiter drops low in the northwest before morning twilight, Saturn, Venus and Mercury will be a tight group low in the southeastern sky early in the month that will gradually spread out as the weeks go by. The highest and faintest will be yellow Saturn, which will rise around 4 a.m. local time as December begins and about 2:30 a.m. by month's end. Viewed through a telescope, the planet's spectacular rings will be tilted 19 degrees toward Earth throughout December.

Venus, by far the brightest of the group, will rise about a half hour after Saturn, and Mercury will follow about 40 minutes later. Each morning Venus will appear lower and Saturn higher, so by month's end the two will be 40 degrees apart and Venus will begin sinking into the glow of morning twilight.

Mercury will have its best morning appearance of the year for observers at mid-northern latitudes, rising unusually high and being easy to locate to the lower left (east) of Venus. The two planets will be closest on Dec. 9. Mercury may be too low to see without binoculars during the last week of December.

Meteor showers

The annual Geminid meteor shower, which will reach its maximum on the night of Dec. 13-14, usually offers the best show of the year, outperforming even the Perseid shower of August. This year the Geminids will peak when the moon is new, so there will be no interference from moonlight. In a clear dark sky, observers may see more than 100 meteors per hour. The nights before and after the peak should also provide good viewing opportunities.

These "shooting stars" will seem to come from a point near the bright stars Castor and Pollux in the constellation Gemini the Twins, which gives the shower its name. This radiant point will be well above the eastern horizon a few hours after sundown and will remain high in the sky for the rest of the night. The higher the radiant is above the horizon, the more meteors there will be. Try facing southeast if you have a clear view in that direction, though meteors will be visible in all parts of the sky.


The sun will be farthest south in Earth's sky at 6:12 a.m. EST (11:12 Universal Time) on Dec. 21, marking the start of winter in the Northern Hemisphere and summer in the Southern Hemisphere. For the next six months in the Northern Hemisphere, the days will be getting longer.

Moon phases

The moon will be at third quarter on Dec. 6, new on Dec. 13, at first quarter on Dec. 20 and full on Dec. 28.