Bakersfield Night Sky – December 18, 2010
By Nick Strobel
The winter break is here now that the kids are out of school for the next couple of weeks. Last weekend I braved the mall. I guess the recession is over because the stores were packed and there were long lines of people waiting at the check out registers---people weren't just looking. That evening the Moon was First Quarter phase to the right of Jupiter. Tonight, the Moon is in a waxing gibbous phase and just below the Pleiades in Taurus. Jupiter will be the only other solar system object you will be able to easily see. It is the very bright star-like object in the south at 6 PM about half-way up in the sky. By 9 PM it will be a bit lower in the southwest but still extremely bright. Its other two evening bright planet companions last month, Mercury and Mars, are now lost in the glare of the sunlight. Just at the edge of visibility on a truly dark sky away from the city lights is Uranus slightly to the left of Jupiter.
In a couple of nights (December 20th) the Moon will be Full Phase and it will be aligned with the Earth-Sun line just right to go into the Earth's shadow---a total lunar eclipse! Unlike a total solar eclipse that lasts just a few minutes with just narrow range of locations on Earth able to view it, a total lunar eclipse lasts for over an hour and everyone on the side of the Earth facing the Moon can see the total lunar eclipse. Those of us in the western United States have the best view of it as the Moon will be high in the south when it is totally in the darkest part of the Earth's shadow, the umbra. I hope it is clear enough to see! The inset of the first chart below shows the times and locations of the Moon at various points during the eclipse, but here are some more details. At 10:33 PM (Dec 20), the Moon begins to enter the Earth's umbra. Those in the umbra of a shadow see the light source completely blocked out, so here, observers on the Moon would see the Sun completely blocked by the Earth. We here on the Earth see a curved dark shadow cross over the Moon from left to right. At 10:33 PM, the Moon will be high in the south at the foot of the twin named Castor in Gemini (the right or western string of stars in Gemini, above Orion's club in his right hand raised up high). At 11:41 PM the Full Moon will be completely in the Earth's umbra still at the foot of Castor high in the south. It will move through the Earth's umbra completely in shadow until 12:53 AM (Dec 21) still at the foot of Castor. From then until 2:01 AM, you will see the edge of the umbra move across the Moon. By 2:01 AM, the Moon will be in the southwest but still at the foot of Castor.
When the Moon is entirely in the Earth's umbra, it will have an orange-red color because some sunlight will get scattered and bent toward the Moon by the Earth's atmosphere. The blue and green colors of the sunlight have a harder time making it through so the oranges and reds dominate what reaches the Moon. If you were on the Moon looking at the Earth, you would see a brillant ring of sunsets and sunrises around the Earth. That is an experience I hope my children or grandchildren get to experience! The actual color of the lunar eclipse depends on the clarity of the Earth's atmosphere---the Moon can be a very dark brown to almost black if there is a lot of dust in much of the Earth's atmosphere such as after a recent large volcanic eruption. So the color of the Moon during a lunar eclipse is one global measure of the pollution in the Earth's atmosphere. The next lunar eclipse is in June 2011 but the other side of the Earth gets to view that one. In December 2011 we will be able to see part of one before the Moon sets and the Sun rises. The next good lunar eclipse for us will be in April 2014.
By the time the lunar eclipse is finished, Saturn will be visible rising in the east near the middle of Virgo. About an hour and half after Saturn rises, Venus will rise right next to Libra. Later that day at 3:38 PM (Dec 21), the Sun will stop its southern drift with respect to the stars and begin moving northward again---the December solstice marks the official beginning of winter for us. South of the equator, people mark that as the official beginning of their summer. The Moon will pass under Venus at the end of the year (see the second chart below).
A few nights after the solstice, many will be hearing stories that include a star that appeared in the night sky to mark the birth of Jesus Christ. For those of you curious to know a possible astronomical explanation of what the star could have been, see my "The Star of Bethlehem" essay on my Astronomy Notes website.
Although we are constantly being bombarded by messages to spend, spend, spend during this holiday season, I hope that you will consider boosting the economy in a different fashion by donating to a worthy charity in honor of someone else. I also hope you all have a blessed, safe and joyous holiday season!
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