MARTIN Lunn, of Earby Astronomical Society, explains what to look out for in the night sky over the coming month.

DECEMBER heralds the beginning of winter; the cold and dark months which might not be to everyone’s taste, but which astronomers like best. There is more time to go stargazing!

If you ever wanted to see a star disappear then reappear, this is the month to be watching. The bright red star Aldebaran in the constellation of Taurus the Bull, which is high in the south, will be occulted by the Moon. This means that the Moon will pass in front of the star. At 6.12pm on December 23, Aldebaran will disappear, then at 7.11pm it will reappear from behind the Moon.

All the main guides, Ursa Major, or the Plough, Orion and Cassiopeia are on view. Orion, the main constellation of winter, is getting higher in the sky and will be at its best after Christmas. Of the stars we see near Orion, only Sirius the Dog Star is difficult to find as it is still very low in the sky.

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 a telescope however you would discover that there are actually about two hundred and fifty stars in the cluster.

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.

What’s up in The Solar System?

The Planets in December

During the autumn season there was a great grouping of planets in the morning sky before sunrise which is now coming to an end. Venus the bright morning ‘star’ is now getting closer to the horizon but is still visible before the Sun rises, and Jupiter is still a morning object but is becoming much higher in the sky. In 2016, however, Jupiter will be visible in the evening sky. Mars can also still be seen in the morning sky but only as a rather faint red looking ‘star’, and like Jupiter, Mars will be visible in the evening sky in 2016.

The other bright planets Mercury and Saturn are too close to the Sun this month and therefore cannot be seen.

Meteor Showers

In December we see the Geminid meteor shower, one of the most spectacular of the year. Many people refer to meteors as ‘shooting stars’ but they have nothing whatsoever to do with stars.

Meteor showers are the dusty remains of comets that travel around the Sun; if the Earth happens to pass through the trail of dust left by a comet we see a meteor shower. However, the Geminids are rather different because they are connected with an asteroid rather than a comet. This particular asteroid is called Phaethon.

On the night of December 13- 14 , as long as the sky is not cloudy, 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 will be unlucky not to see at least one Geminid.

Don`t forget if you see a shooting star, you know what you have to do - make a wish!

Phases of the Moon for December

Last Quarter 3rd, New Moon , December 11 First Quarter, December18, Full Moon, December 25.

This month’s full moon is called the Long Nights Moon, this is because December is when winter begins and nights are at their longest and darkest.

The Shortest Day

The winter solstice occurs on December 22. This is the time when we have the shortest day of the year. From this point on the Sun will slowly get higher in the sky and daylight will lengthen.

The next meeting of the Earby Astronomical society will be at All Saints’ Church, Earby, tomorrow from 7.30pm to 9pm. The speaker will be Martin Lunn MBE FRAS, Earby Astronomical Society, and the title of the talk will be The Winter Sky.