Martin Lunn, of the Earby Astronomical Society, looks at what the skies will hold in the coming month

WE ARE nearly into the winter night sky. Orion is now well above the horizon and will be at its best after Christmas.

Most of the bright constellations of winter are now visible. With Orion (the Hunter) are Perseus, Taurus (the Bull), Auriga (the Charioteer), Gemini (the Twins) and Canis Minor (the Small Dog). Canis Major (the Large Dog) with Sirius the Dog Star is not really on show yet.

The Plough, or Ursa Major, is still low in the North. Americans refer to the Plough as the Big Dipper. The ‘W or M’ of Cassiopeia is still overhead. Of the Summer Triangle’ only Deneb is now really visible. The Square of Pegasus, symbol of autumn, although still visible is now past its best in the south west.

What’s up in the solar system?

The Planets in December

There are subtle changes in the night sky this month. Venus is now becoming visible in the south west just after sunset at around Christmas. It will appear as a very bright ‘white star’. Any bright star like object in the sky at this time of year will always make people think of the ‘Star of Bethlehem’ which was seen by the wise men. However, astronomers living at the time of the birth of Jesus would have recognised Venus as a familiar object. The ‘Star of Bethlehem’ must have been something unusual, but was it a real star?

Jupiter is now becoming more conspicuous in the evening sky. It rises at about 8.30pm and will dominate the sky before and after Christmas. While Mars is briefly visible in the west just after the Sun sets, Saturn is just visible before the Sun rises. Both planets are not very bright and will be difficult to see. Sadly Mercury won’t be visible again until next year.

Meteor Showers

On the nights of December 13/14 and 14/15, providing the skies are clear, it will be possible to see lots of Geminid meteors .When a comet travels around the Sun it leaves a trail of dust behind it. If the Earth passes through this dust trail some dust particles will burn up in the atmosphere and we will see lots of ‘shooting stars’, or meteors. The Geminid meteor shower is so named because all the meteors appear to be coming from the constellation of Gemini. This is a spectacular meteor shower.

The Geminids are slightly different from most meteor showers as the trail of dust comes not from a comet but from an asteroid called Phaethon and because the grains of dust are slightly larger than usual the Geminids are usually very bright. The Geminids can be seen anywhere but if you look up to a height of about two thirds of the way up in the sky from the horizon you will have the best chance of seeing some Geminids.

Phases of the Moon for December

Full Moon 6th, Last Quarter 14th, New Moon 22nd, First Quarter 29th

The full Moon this month is called the Before Yule Moon. Tradition says that between the full Moon in December and the feast of Yule on December 21st people had to go into the forest to chop down a tree to get their Yule Log to burn over the Christmas period.

The Winter Solstice, the shortest day, occurs on December 21. This festival has pagan roots, often being referred to as the feast of Yule or ‘Sol Invictus, The Undefeated Sun’. From this date the Sun climbs higher in the sky.

The next meeting of Earby Astronomical Society will be on Friday, November 28, at All Saints’ Church, Earby, from 7.30pm to 9pm. The speaker will be Prof Philippa Browning, from the University of Manchester, and the talk will be on ‘The Active Sun’.