Filled with shooting stars and Jovian moons playing tag, some of the most sparkling gifts of this holiday season can be found this week in the night sky.
Full Moon with Stellar Beacons. As the sun sets on Monday, December 16, a full moon rises in the east – the smallest of 2013. Despite the bright glare, four brilliant stars will appear to surround Earth’s lone natural companion in the evening sky.
Look for orange-hued stars Aldebaran and Betelgeuse, above and to the right of the moon, while white-colored Capella and the planet Jupiter appear to the far left and below.
Jupiter’s Moon Shadow. Late evening on Tuesday, December 17, look for the gas giant Jupiter rising high in the east.
Starting at 10:04 pm EST, backyard telescopes will show the outermost Jovian moon Callisto cast its shadow on the planet’s cloud tops—its dark, pin-prick silhouette will take a full three hour to cross Jupiter—followed by the moon itself crossing into the disk of Jupiter an hour later.
Moon joins Jupiter. Late evening of Wednesday, December 18, look for the gas giant Jupiter to have a close lunar encounter high in the eastern sky. The celestial pair will appear only 5 degrees apart—equal to the width of your fist at arm’s length.
Of course, their proximity to each other is just an illusion. Jupiter is some 1600 times farther away from Earth than our moon.
Winter Solstice. At exactly 12:11 pm EST on Saturday, December 21, the sun is at its lowest in the sky, making it the shortest day of the year north of the equator. Meanwhile today is the longest day in the Southern Hemisphere.
During winter the Earth’s northern axis is tilted away from the Sun and so the Northern Hemisphere receives less sunlight.
The exact date and time of the winter solstice, while it always fall around December 21, slightly changes from year to year because of the difference between a calendar year of 365 days, and the solar year of 365.26 days—the exact time it takes for the Earth to make one trip around the Sun.
Ursid Shower Peaks. In your local pre-dawn hours of Sunday, December 22, a minor meteor shower peaks in the northern skies.
As with all meteor showers, the Ursids are named after the constellation they appear to radiate out from in the sky, in this case Ursa Minor, the little bear. Meteors appear to shoot out from a region of sky just above the bowl of the Little Dipper.
While the Ursids only produce on average about 10 to 15 shooting stars per hour at rare times there are bursts of 30 or more per hour. The parent comet is 8P/Tuttle and Earth plows through the debris shed from this icy visitor between December 17 and 23.
This year meteor watchers will have to contend with a waning gibbous moon which rises the night before at around 9 pm. So expect to see more modest numbers than usual, somewhere around 5 to 10 per hour.