Star Trak: January 2018

BLOOMINGTON, Ind. -- Two pairs of planets will brighten the morning skies of January.

Huge white Jupiter and red-orange Mars will be the first to appear at the start of the month, rising together around 3 a.m. EST just 2 degrees apart. For observers around 40 degrees north latitude, the pair will be more than 30 degrees high in the south-southeast 45 minutes before sunrise.

Both will increase in brightness as the month passes, but Jupiter will greatly outshine Mars. The two planets will be less than 1 degree apart from Jan. 5 to 8, making a striking pair in the field of view of a telescope. By the end of January, Jupiter will rise around 1:30 a.m. local time, and Mars an hour later. Both will be overhead in morning twilight.

Mercury and Saturn will form the second pair of planets, but they will be much closer to the eastern horizon. Mercury will be 23 degrees west of the sun on New Year's Day, and it will continue there for a few weeks until it is too low to find in the brightening morning twilight. Saturn will be hard to locate during the first week of the month, but it will gradually get higher and easier to spot.

At their closest on Jan. 13, Mercury and Saturn will be only 0.6 degrees apart. Mercury will be brighter, but both will be low in the southeast a half-hour before sunrise. That will change by month's end, when Saturn will rise more than two hours before the sun.

Venus will be out of sight all month as it passes on the far side of the sun from Earth. It will reappear low in the evening sky in late winter.

Meteor shower

The Quadrantid meteor shower will be active for the first week of January, peaking during the hours before dawn Jan. 4. The moon will be nearly full, so moonlight will wash out the fainter meteors. Observers with a clear dark sky may see up to 20 bright meteors per hour shortly before the start of morning twilight. 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.

Try facing 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 is available from the American Meteor Society.

Lunar eclipse

The first total lunar eclipse in more than two years will be visible over the west coast of North America and the Pacific Rim on Jan. 31. Observers along the east coast and in the Atlantic region will miss most of the show. See this NASA site for details of where and when the eclipse can be viewed.

Perihelion

Earth will be closest to the sun in its orbit, the position called perihelion, at 1 a.m. EST (6:00 Universal Time) on Jan. 3. A common misconception is that our seasons are caused by Earth's changing distance from the sun, but the actual cause is the tilt of Earth's axis. In the Northern Hemisphere, winter happens when the North Pole is tilted away from the sun, so sunlight must pass through more of Earth's atmosphere to reach the surface. We experience the coldest time of year when we are closest to the sun.

Moon phases

The moon will be full on Jan. 1, at third quarter on Jan. 8, new on Jan. 16, at first quarter on Jan. 24 and full again on Jan. 31.

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Hal Kibbey

Phone: 812-336-1333

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Email: hkibbey@indiana.edu

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