The Night Sky This Month: December 2014

Geminids
Geminid Meteor Shower at Topaz Lake in the Eastern Sierra region on the California-Nevada border by www.JeffSullivanPhotography.com

Ursids Meteor Shower

There are plenty of astronomical events taking place in December for stargazers to enjoy, not least the Ursids Meteor Shower, which runs from Dec 17-25, but peaks when the Moon is New and invisible on December 22/23. Although it is only expected to reach about 5-15 meteors per hour, the meteors can be spectacular to watch, and occasionally can be quite plentiful with a surprise high volume for those turning their attention towards the constellation Ursa Minor. The Ursids Meteor Shower is caused by dust left behind by comet Tuttle, which was first discovered in 1790.

Geminid Meteor Shower

Of course, with winter upon us, our old friend Orion the Hunter is back in the sky, and from the 8th to the 17th, just above his left shoulder, is the radial point for the Geminid Meteor Shower. This shower peaks on the 14th and can have 100-120 meteors per hour, usually of the bright and slow variety. Most meteor watchers refer to this as the King of Showers.

However, be warned it is going to be a bit bright with a Last Quarter Moon occurring on December 14th, so look high and away from its glare. A rural observing location well away from towns or cities will also pay dividends. This Geminid Meteor Shower is unusual, as most meteor showers come from comets, but in the case of the Gemenids is caused by the Earth crossing the orbital path of asteroid 3200 Phaethon, a mysterious body called a rock comet.

It may once have been a typically icy body comet, but all its volatiles have boiled away leaving just the rubble behind. Every 1.4 years, this small 5-kilometer rock closes in its orbit to within one-third of Mercury’s distance to the Sun. This causes intense thermal fracturing, making 3200 Phaethon shed rubble into its orbital trail.   Earth’s upper atmosphere then smacks into this junk at some 130,000 kilometers per hour, to vaporise as the colorful Geminid meteors. Dress warmly, wear a hat, and take some cocoa or tea with you in a good vacuum flask.. It will be cold!

Ursa Major And NeighboursA 118 Mile Asteriod In Eridanus

If you have a telescope at hand, December 1st offers an opportunity to view one of the larger asteroids in the Asteroid Belt, which lies between Mars and Jupiter. Hebe is 118 miles long and is currently floating down the “river” of Eridani. At Magnitude 8, picking it out of the background of the constellation Eridanus can be very exciting.

Jupiter

Jupiter is back and brightening as well. It is currently at mag. –2.3 but will be –2.5 fairly quickly and stay that way for the month. It rises in the ENE sky in mid-evening, sitting just to the right of the constellation Leo, and about 4 finger-widths (8°) NW of the star Regulus.  It will be high in the south by 5 a.m. and fairly conspicuous in the SW just before dawn.

Jupiter will be close to the Moon on the 11th, just a tad over 715 million kilometres distant. With a nice telescope you should have no trouble picking out a couple of Jovian moons.

Mars

Mars is still visible in the evening, low in the SW, but will track ENE through Capricorn on the 4th and dim to magnitude 1.1. It should be gone (set) by 7:30 p.m.

Venus

The Evening Star, Venus, is brilliant at mag –3.9 around sunset, low in the SW sky. It will be about two finger-widths (4°) above the horizon and three-and-a-half (7°) by the year’s end.

Saturn

If you happen to be up an hour before sunrise in the early part of the month, you should be able to catch a glimpse of Saturn, and as much at 180 minutes before sunrise by the end of the year.

International Space Station

If you want to spot the International Space Station pop over to this link, pick your location, country, city, and read the times available for observation. It’s usually best seen at dusk or dawn when the sun is below the horizon and lights it up fairly well.  The period is usually only 1 to 4 minutes, which is plenty of time for binoculars, and possible even with a fairly large reflector telescope so you can see more than a bright spot. Its current position can be found here.

Winter Solstice

December 21st occasions the December Solstice, or Winter in the Northern Hemisphere and Summer in the Southern Hemisphere. This gives us the longest night and shortest day in the north and conversely, the longest day and shortest night in the south.

Early January Note:

Look out for the Quarantid meteors around January 3rd-4th!