The Free Press, Mankato, MN

December 2, 2010

December Starline: Mother nature offers celestial presents

By Steve Kipp
Minnesota State University

— If you go outside in the morning around sunrise you can see brilliant Venus high in the southeast like the star at the top of nature’s Christmas tree. Venus reached its maximum brightness on December 4. The bright “star” above Venus is Saturn.

       The year’s second best meteor shower, the Geminids, peaks between late night December 13 and the early morning hours of December 14.  The moon will have set and at a dark location you might see up to 60 colorful meteors per hour.  Geminid meteors are often yellow but green and blue meteors are also seen. Meteors will be seen streaming from the direction of the constellation Gemini, above and to the left of Orion in the sky. Geminid meteors are produced by particles from the asteroid 3200 Phaethon.

       Phaethon is a strange object. Meteor showers are usually associated with comets, icy objects that gradually fall apart as they orbit the sun producing trails of icy particles. The particles are swept up by the Earth and are seen as meteors. But Phaethon has the characteristics of a rocky asteroid. In fact it is the asteroid that comes closest to the sun and is named after the son of the Greek sun god who drove the sun chariot too close to the Earth. Perhaps the colors of the Geminid meteors come from the unusual compositions of the particles it leaves behind.

        On December 20 the full moon will rise in the east around sunset. The moon will be located just above Orion in the winter sky. Just before midnight, about 11:29 p.m., the moon will move  into the Earth’s penumbral shadow and the second lunar eclipse of the year will be underway. The penumbral shadow isn’t very dark so you probably won’t notice the beginning of the eclipse till about 12:32 a.m. when partial eclipse begins as the moon moves into the Earth’s dark umbral shadow. Maximum eclipse will occur at 2:17 a.m. The fully eclipsed moon will appear a shade of red from pink to ruddy brown depending on the amount of dust in the Earth’s atmosphere. Compare the color of the eclipsed moon to the color of the nearby bright red star Betelgeuse in Orion.  The eclipse finally ends at 5:04 a.m. with the moon setting in the west.

       The eclipse ends the day winter begins. The winter solstice falls December 21 at 5:38 p.m.  On the solstice the sun is as low in the sky as it ever gets and the length of daylight is shortest.

       On December 22 the Ursid meteors peaks. The Ursids is an erratic meteor shower associated with comet Tuttle. Ursid meteors radiate from the direction of Polaris, the north star.

       You may have noticed that a leap second is sometimes added to the end of the year to allow the rotating Earth to catch up to more regular atomic time. The Earth’s rotation has not slowed enough recently so no leap second will be added this year. The last leap second was added at the end of 2008.

Send comments and questions to Steve Kipp, at steven.kipp@mnsu.edu