December is the darkest month of the year. The winter solstice happens on Dec. 21, bringing with it the shortest day of the year and the longest night. From that date onward the days will slowly get longer.
In December the night sky is spectacular. The brightest stars we see all year are in their glory. As an added treat, all five of the brightest planets will be visible.
In the early part of the month, look for Saturn low in the southwest just after it gets dark. It is dropping into the sunset glow so this is your last chance this year to see those famous rings. If you have a small telescope packed away in your attic somewhere, now is the time to dig it out.
Towards the end of December the elusive and seldom-seen planet Mercury will make an appearance low in the west just after sunset. Start looking for it about 30 or 40 minutes after the sun has disappeared and while the western sky is still glowing in the twilight. You have to be somewhere where you can see low into the southwest.
The best way to find Mercury is to first look for its much-brighter companion, Venus. She has just rounded the far side of the sun and is returning to our evening skies until next summer. Mercury, which will only be around for a couple of weeks, will be near Venus.
Christmas present
On the evening of Christmas Eve, a special grouping of Venus, Mercury and a very slim crescent moon will be delicately placed low in the west just after sunset. Venus will be the brightest and easiest to see with dimmer Mercury just above. The moon, which will be a super new moon, will be just to the left. A pair of binoculars will come in handy and a view low to the southwest is a must.
Much higher in the south, Jupiter is easy to pick out. Notice that it is not twinkling, a dead giveaway that it is a planet, not a star. Named for the Roman name of the king of the gods, be sure to point that telescope at Jupiter. Its four large moons which circle the planet are easy to spot. Also look for the cloud bands stretching across Jupiter itself.
There is a distinctly red object rising in the east shortly after sunset. Notice it is not twinkling either, so it must also be a planet. What planet is red? You guessed it, Mars! Mars was named for the fearsome god of war probably for its blood-like color. In December it will be at its closest to us until the year 2037. Now is a great time to check it out with that telescope that you have hopefully found in your attic by now. If you are lucky you might see one of the polar ice caps and maybe some of the dark markings on the face of the planet.
An occultation
On the night of Dec. 7, Mars will be occulted by the full moon. Wondering what that word that starts with an “o” means? Hidden. The moon will slide right over Mars, hiding it for maybe as long as an hour. Then the red planet will reappear on the other side of the moon.
Start watching for the occultation as soon as the moon is visible in the east. It may already be in progress before you can see it. That telescope will be perfect for watching the moon gobble up Mars, which will take almost a minute. As winter progresses and the Earth pulls away from the red planet, it will fade and become less interesting than it is right now.
Want to see the brightest star in the sky? In December, go out a little later at night, maybe 9 or 10 p.m. A bright white twinkling star will be coming up in the southeast. So why do stars twinkle and planets do not? Some things in astronomy are complicated and difficult to understand, but not this one. It is because “Twinkle, twinkle little planet” does not rhyme with “How I wonder what you are.”
That star is Sirius and its name comes from a Greek word meaning the “scorcher.” Is it a really bright star or does it just happen to be close to us? It is hard to tell looking at it because the sky appears two-dimensional to us. Humans are a clever bunch, and using the orbit of the Earth around the sun as a base for a very long and skinny triangle, we have figured out that Sirius is quite close to us. Book a Delta Airlines flight for the trip and it will only take about 10 million years to get there.
Look to the right and above Sirius for the bright stars of Orion. Notice that the three distinctive stars of his belt point right at Sirius. That is how you will know you are looking at the brightest star in the sky. Have fun out there and do not let your feet get cold standing in all that snow.
