December skies offer something for everyone with variety of objects
The last month of the year offers up a great variety of objects to view from our Arizona skies.
During 2018, I have been providing you with some of the most important news and observational information to help you get the most out of the rich dark skies that are still a great resource for people to enjoy.
As we enter December, we begin with the moon, the nearest celestial object to Earth.
The moon starts December as a thin waning moon visible just before dawn and then moves on to its new phase, or the dark of the moon, on the Dec. 7.
This is the beginning of lunar cycle 1187. The first recorded lunar cycle occurred back on Jan. 17, 1923. That is not the first time the moon showed a phase, but simply a recording system for modern record keeping.
Look low in the southwest sky at sunset on the night of Dec. 8 for a very thin waxing crescent moon. The next night will bring a close conjunction of the moon and Saturn in the southwest sky.
A splendid first quarter moon occurs on the evening of the Dec. 15, as the moon then appears half illuminated. Then comes the full phase for December with the arrival of the Full Cold Moon on Dec. 22. The winter solstice occurs some 19 hours before this full moon.
The last quarter moon occurs Dec. 29.
The moon will be farthest from us (apogee) on Dec. 12 and nearest to us (perigee) on Dec. 24.
December is a great month for planets, too.
Look low in the south at sunset for Mars. It is moving away from us and is well over 93,000,000 miles from Earth.
Mars, visible to the naked eye, is now home to the amazing NASA InSight lander.
Light takes nearly nine minutes to travel to Mars at this time.
The predawn skies also offer some great planets to look at.
The innermost planet, Mercury, will be making a great showing in the predawn sky by Dec. 15. Look some 20 degrees away from the rising sun in the southeast sky.
By far, the best planet to view in the morning sky is Venus. It is visible high in the southeast sky at dawn. Venus can be bright enough to cast a faint shadow on a snow field in dark moonless skies.
Venus is now some 38,000,000 miles from Earth and the planet that can get closest to us.
At its closest, Venus can come within 25,000,000 miles of Earth.
December is also known for the Geminid meteor shower. For a chance to see this shower, look to the northeast sky around 10 p.m. The best nights for this will be Dec. 13 and 14.
Geminid meteors come from an ancient asteroid or comet known as 3200 Phaethon.
One last object to look out for is the small yet interesting periodic comet called 46P/Wirtanen.
It has an orbital period of 6.7 years and may be the brightest comet of 2018.
The comet will pass within 7 million miles of Earth on Dec. 16 and could be bright enough to be seen with binoculars from Dec. 13 to at least Dec. 25.
It will be placed close to the Pleiades star cluster on the night of Dec. 16 and close to the bright star Capella on the night of Dec. 24.
Learn more about Comet 46P/Wirtanen and view the finder charts here.
We finally welcome in the season of winter, with the winter solstice on Dec. 21 at
3:23 p.m. MST.
Clear skies and happy holidays to all!
To print your own monthly star chart, click here.
To view satellites/dates/times of passage, click here.
Listen to the Dr. Sky Show on KTAR News 92.3 FM every Saturday morning at 3 a.m.