Bakersfield Night Sky – December 4, 2010
By Nick Strobel
This week ended the last regular class meetings at Bakersfield College for the Fall semester. This next week brings the crush of final exams but after that I have the chance to take care of things that I have put off since August including some things that have been on the "honey-do" list for a while. Fortunately, my wife is also a teacher and understands what a "full-time" teaching load means. Last Thursday was the first showing of the annual "Season of Light" program at the planetarium and this coming Thursday is the final showing. Although last Thursday's show was sold out, there are still tickets left for the December 9th show (as of the time I wrote this).
The first part of December has just two planets visible in the evening: Jupiter in the south and Mercury low in the southwest. Mercury will be visible for up to about half an hour after sunset this evening but starting mid-week it will plunge very quickly back toward the Sun and get lost in the glare of the Sun. On December 7th, the very thin Waxing Crescent Moon will be about a fist-width at arm's length to the upper left of Mercury. The previous evening (December 6th), an even thinner crescent Moon will cover up Mars but both will be so close to the Sun on our sky that you won't be able to see the two without the help of a telescope. Mars is essentially not visible for the month of December since it is going behind the Sun. It will pass behind the Sun the first week of February so it will also not be visible for the months of January and most of February. Early morning risers will be able to see Venus and Saturn in the east starting around 4 AM. Between them will be the bright star Spica of Virgo.
The Moon will be in first quarter phase on December 13th (actual first quarter phase is at 5:59 AM). The Moon will be above Jupiter in the middle of the right-most fish of Pisces. December 13th is also the first night of the peak of the Geminid meteor shower. The peak continues to December 14th and then falls off over the following couple of nights. The Geminids usually put on a good show but you'll need to observe them under a dark sky away from the city lights. They are the result of the Earth running into the dust trail left behind by 3200 Phaethon, an asteroid that is probably a "dead" comet that has lost all of its volatile material from repeated passages around the Sun. The Geminids get their name from Gemini which has risen by about 8 PM in the northeast. If you trace the meteor streaks backward, the paths will appear to intersect at a point ("the radiant") near Gemini's second-brightest star, Castor---see the attached star chart. The attached chart shows the sky for 9 PM looking east. Castor and Gemini's other bright star, Pollux will make a vertical line at that time with Castor above Pollux. The radiant of the Geminids is slightly above Castor. The Geminids can produce up to about 100 meteors per hour. You will probably need to wait until the bright Moon sets at around 12:30 AM on December 13th and 1:30 AM on December 14th to get a decent view.
To the right of Gemini will be the bright constellation Orion with his belt stars making an almost vertical line that points down to the brightest star in the night sky Sirius and points up toward the bright orange Aldebaran at the eye of Taurus and further up to the star cluster Pleiades at Taurus' shoulder. Above Gemini you will see the bright star Capella at one point of the pentagon shape of Auriga.
Later this month the Moon itself will put on a nice show for us as it passes through the Earth's shadow to make a total lunar eclipse. You will see the Moon enter the dark part of the Earth's shadow (the umbra) at 10:33 PM on December 20th and the Moon will be entirely inside the umbra from 11:41 PM to 12:53 AM December 21st. Light from sunsets around the globe at the time the Moon is in the umbra will cast a orange-red color on the Moon. Most of the western hemisphere will be able to witness the show.
Want to see more of the stars at night and save energy? Shield your lights so that the light only goes down toward the ground. See www.darksky.org for how.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com