Thursday, December 10, 2009

Mercury in December Skies

By Jon Spargo
Tech Astronomy Club

Tiny but bright Mercury puts in an evening appearance this month for about the first three weeks. Shining at magnitude -0.5 it will be best viewed around the 12th when is should be seen as a bright dot about 6 degrees above the southwestern horizon about a half hour after sunset.
Jupiter still shines brightly in the early evening sky but will set around 8:30 p.m. by the end of the month. The best viewing will be early evening while it is still relatively high in the sky. For a good part of the month a bonus will be that the planet Neptune will be within one degree of Jupiter and only 0.6 of a degree for several days surrounding the 21st. For those with telescopes, the tiny blue sphere of Neptune will be found slightly above and to the right of Jupiter.
Now is the time to view Mars in spite of all those bogus emails that flooded the Internet last summer. Mars will continue to rise earlier each evening and by the end of the month will do so only 3 hours after sunset. We can also watch as Mars’brightness grows to magnitude -0.7 as the Earth begins to catch up to Mars. However, the closest approach of the Earth to Mars (in January) will see Mars appear only half as big as it did in the summer of 2003.
On Dec. 21, we will experience the shortest day of the year as the winter solstice begins at 10:47 a.m. MST. For folks “down under” it’s “put another shrimp on the barbie mate, summer has officially begun!”

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