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Hal Kibbey

Last modified: Thursday, January 1, 2009


The International Year of Astronomy begins

Jan. 6, 2009

BLOOMINGTON, Ind. -- The International Year of Astronomy will begin with Mercury and Jupiter next to each other low in the southwest shortly after sunset. Far to their upper left (south) will be Venus, a brilliant "evening star" dominating the southwestern sky. Saturn will rise in the east around midnight.


Mercury, the smallest planet, can be hard to find by itself. This will be a fine opportunity to see it using much larger and brighter Jupiter as a nearby marker. Mercury will be highest above the horizon on Jan. 4, when it will set 90 minutes after the sun. Then it will start downward again, and by Jan. 15 it will be hard to find in the bright twilight. Mercury will pass between the sun and Earth on Jan. 20.

Jupiter will join Mercury on Jan. 1, shining three times more brightly. Each night after that, Jupiter will sink lower and become harder to locate.

Venus will blaze well up in the southwest all month. It will be the brightest point of light in the sky, shining through the afterglow of twilight a half hour after sunset.

Saturn will rise in the east around midnight local time at the start of the month and two hours earlier by month's end. Saturn will dominate the stars of the constellation Leo the Lion. Wait until Leo has completely cleared the horizon before you turn a telescope on Saturn, to avoid seeing the turbulence in Earth's atmosphere that will otherwise blur your view of the planet.

By 2 a.m. local time, Saturn will be more than halfway up the southeastern sky. When Saturn is high in the south on a clear night, there is no better opportunity to view it with a telescope. That view will be unusual this month because Saturn's rings will be almost edgewise to us and therefore nearly invisible. So, the entire planet will be revealed instead of having much of one hemisphere blocked by the tilted rings. Saturn's largest moon, Titan, will appear close to the planet on Jan. 7, 8, 15, 16, 23 and 24.

Mars will remain out of sight all month as it passes behind the sun.

Meteor shower

The Quadrantid meteor shower will be active for the first week of January, peaking during the frigid hours before dawn on Jan. 3. The moon will set before that time, so viewing conditions will be favorable if the weather cooperates. The rate of this shower varies considerably and unpredictably from year to year, but observers may see up to 100 meteors per hour during the brief two-hour peak.

The Quadrantids will appear to come from a point called the radiant near the end of the handle of the Big Dipper, which will rise in the northeast. The radiant is in the constellation Bootes the Herdsman, which contains the bright orange star Arcturus as a conspicuous marker. In the 18th century, this area of the sky was called Quadrans Muralis and gave the Quadrantid meteor shower its name.

Try facing northeast toward the Big Dipper. If you extend the curve formed by the handle's three stars, it forms an "arc to Arcturus." Meteors should be visible in all parts of the sky, but the higher Arcturus is above the eastern horizon, the more meteors there will be. More information about viewing meteor showers, including the Quadrantids, is available from the American Meteor Society at


On Jan. 4, Earth will reach its closest point to the sun in its orbit, the position called perihelion. A popular misconception is that our seasons are caused by Earth's changing distance from the sun. The actual cause is the tilt of Earth's axis. Winter in the Northern Hemisphere happens when the North Pole is tilted away from the sun, so that sunlight must pass through a greater amount of Earth's atmosphere to reach the surface. We experience the coldest time of year when we are closest to the sun.

Another "leap second"

Earth's spin is gradually slowing down because of tidal friction. To keep clocks in close step with the turning of the planet, every now and then officials at the International Earth Rotation and Reference Systems Service add a "leap second" to Universal Time. This happened again on New Year's Eve at 23:59:59 UT (6:59:59 p.m. Eastern Standard Time). The previous leap second was added at the end of 2005.

The U.S. Naval Observatory in Washington, D.C., is the world's leader in maintaining and correcting time standards. More information is available at

Moon phases

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