We have very long nights in the northern hemisphere during December - perfect for astronomy! Here in Greenwich, the sun is setting at 4pm in the afternoon and not rising again until 8am - giving 16 hours when the Sun is below our horizon. When you take evening and morning twilight into account, we have 14 hours of beautiful star-filled darkness... if you can get far enough away from light pollution.

The long nights are due to the Earth being tilted by 23.5°. In December, the northern hemisphere of the Earth is pointing away from the Sun, so the Sun appears much lower in the sky, and its warmth is diminished.

Jupiter & Venus are the highlights this month, visible low in the west in the evening sky, just after sunset. While Jupiter stays low throughout the month, Venus gets higher in the evening sky every day, as it orbits around the Sun.

And on the 27th of December, Venus is next to Neptune, making Neptune unusually accessible. Just find Venus, the brightest thing in the sky, and then look to the top-right slightly (about two finger widths at arms length) and see if you can see Neptune. If you live well away from any light pollution, you may be able to see it with you own eyes (although it is at the very limit of human visability!); otherwise, try using binoculars or a telescope.

It is also the time of year when we are further away from the centre of our Milky-way galaxy, and the galactic centre is hidden behind the Sun.

In the early evening around 6pm, we look westwards to see the patch of sky that used to be directly above us in winter. So, ironically, the Summer Triangle is visible throughout winter! In fact, from the UK, Deneb is a circumpolar star - meaning that it never sets below the horizon.

During December, we have four hours after sunset to see the Triangle before it follows the Sun below the horizon. By February however, you will only be able to see the Triangle in the early morning sky, just before sunrise. Read last months' posting to read about the interesting objects in the Summer Triangle.

Look East in the evening, and you are looking directly out into deep space, towards the constellation of Orion. At the bottom of Orion, to the left of Rigel, is the Orion nebula - a cloud of gas and dust, collapsing to form the latest generation of stars, recycling materials from old, now dead, stars. And you can see that for yourself with binoculars.

Here's to dark and clear skies in December!