Backyard Stargazer for December 2017
By Francis Parnell
It’s December and Christmas will soon be here; it’s also “SUPER MOON” time.
The Full Moon on the 3rd is the largest and closest at 222,133 miles this year! Watch it rise behind distant trees and buildings and you might experience the “Moon Illusion.”
At dawn on the 13th, a very thin crescent Moon is about 5-degrees above reddish-orange Mars in the east-southeast.
The annual Geminid meteor shower peaks on the night of the 13th/14th. Start watching about 10 p.m. on the 13th. Under dark skies – good luck finding them around here – the rate at the zenith for a single observer is about 120 per hour. This shower is known for its brilliant Fireballs (very bright meteors!). Don’t watch one area of the sky; scan in all directions. You never know where you’ll see a bright Fireball flash across the sky!
At dawn on the 14th, an extremely thin crescent Moon can be spotted 4-degrees above yellow Jupiter and 9-degrees below Mars.
On the 20th at dawn, look southeast to find bright yellow Jupiter less than 1-degree away from Zubenelgenubi, the Alpha star in LIBRA, the Balance. Actually, both Zubenelgenubi, the Southern claw and Zubeneschamali, the Northern claw were originally part of SCORPIUS, the Scorpion. Many ancient cultures used the “Claws” as a separate constellation, but it was the classical Roman astronomers that turned LIBRA into the constellation of the Zodiac that we know today.
The Sun is at the Solstice at 11:28 a.m. on the 21st, marking the official start of Winter in the northern hemisphere. The Sun on the first day of Winter, rides low in our sky, about 32-degrees above the horizon. The opposite occurs 6-months later when the Sun is 79-degrees above the horizon on the first day of Summer.
Because of the 23.5-degree tilt of the Earth’s axis to the plane of its orbit, there’s a 47-degree swing of high/low Sun during the year. As the Sun is low in winter, the Full Moon is high in our sky; in summer the Sun is high and the Full Moon is low on our horizon. If there’s a Full Moon around the time of the Equinoxes, as the Sun sets in the west, the Full Moon rises in the east.
At sunset on the 30th, a fun event takes place for small telescope users. The 90% sunlit Moon occults (hides) Aldebaran, the brightest star in TAURUS, the Bull. Start watching a little before 6 p.m. and you’ll see the star wink out as the dark limb covers it. This ol’ stargazer is very familiar with this type of lunar event. For 25 years I timed over 3000 lunar occultations/reappearances for the U.S. Naval Observatory and the International Lunar Occultation Center in Japan. For me, stargazing, and contributing to science, was a heck of a lot of fun!
Merry Christmas and “Keep looking up!”