This month heralds the beginning of winter; the cold and dark months which might not be to everyone’s taste, but they are what astronomers like best. There is more time to go stargazing!
The Plough is now standing on its handle in the north. Capella, the bright yellow star, is not yet at the overhead point but it is very high up and cannot be missed. The twins of Gemini, Castor and Pollux, are much higher. Now is a great time to look for the Pleiades, or Seven Sisters, which are in the sky, looking south. This is a cluster of stars moving through space together. If you have good eyesight it is easy to see the seven brightest members of the Pleiades, using binoculars or a telescope however you would discover that there are actually about two hundred and fifty stars in the cluster.
The regular constellations of winter, Orion, with his two hunting dog Canis Major and Canis Minor. dominate in the south. Leading the way for Orion is Taurus. Dominated by the red star Aldebaran. Auriga the charioteer is almost overhead
Of the summer triangle Altair is no longer visible, Vega is very low in the sky, and Deneb can still be found in the north west.
The planets :-
Very low in the south-west in Sagittarius, keep an eye on the giant Planets. Jupiter at magnitude –2.0 and Saturn, which is ten times fainter with a magnitude of +0.6. Both planets will be falling below the horizon about 6.30pm. As this month progresses the two creep ever nearer to one another. On 21st December they are just 6 arcminutes apart. To the naked eye they will almost seem to merge together. Though they are right on the horizon use a telescope for this unique opportunity to see the stripy disc of Jupiter and Saturn’s rings in the same field of View. This will be the closet encounter between the two since 1623.
Mars is brilliant in the southern sky, though fading from magnitude –1.1 to –0.2 during the month. Setting about 2.30am located in Pisces.
Lying in Aquarius, Neptune is below naked eye visibility at magnitude +7.9. It sets around 11pm.
Setting about 4am, Uranus lies in Aries at magnitude +5.7.
Venus is a glorious Morning Star, rising in the south-east around 5.30am. On the morning of 24th December, Venus passes above Antares.
Mercury is too close to the Sun to be seen this month.
On the 12th December the crescent Moon hangs to the upper right of Venus in the morning sky.
On the 17th December the thinnest crescent Moon lies just to the left of the close pairing of Jupiter and Saturn.
21st December at 10.02am, is the winter solstice, when the sun reaches its lowest point in the sky as seen from the northern hemisphere, giving us the shortest day and the longest night.
On the 23rd of the month, Mars lies above the Moon.
During the course of the night of 13th into the early hours of the 14th of this month, will be the maximum of the spectacular Geminid meteor shower. When the Earth hits a stream of interplanetary debris from the asteroid Phaethon.It’s a perfect year for observing this prolific display, as the Moon is well out of the way. Around 100 meteors per hour might be observed from around 10 pm onwards. As the grains of dust are from an asteroid they are slightly larger than those from a comet, so the Geminids can produce many bright white coloured fireballs in the sky. Look up in any direction and you might be lucky to see at least one Geminid.
Phases of the Moon for December:-
December 8th – Last Quarter
December 14th – New Moon
December 21st – First Quarter
December 30th – Full Moon