Welcome to the December night sky. This month we have no bright planets easily visible in the early evening sky, but that is made up for by the opportunity to spot the faint and distant giant gas planet Neptune.
On the night of December 7, Neptune will be very close to the red planet Mars. They are both in the constellation of Aquarius and they will be seen due south as darkness falls.
On that night, through a small telescope or large binoculars, Neptune will appear as a faint bluish star very close to Mars. The planet Mars will be much brighter than Neptune, but you should be able to see the orange colour of Mars and the bluish colour of Neptune.
On the night of December 13-14, the best meteor shower of the month will be visible. They are called the Geminids and it is an unusual shower as the dust that enters our atmosphere to create the shooting stars comes from the asteroid Icarus rather than a comet.
On the 21st, we have the winter solstice when the Sun will be at its lowest point in the daytime sky in the northern hemisphere. This marks the beginning of winter and the longest nights of the year.
This December we may get to see a Christmas comet, as a short period object called 46P/Wirtanen will pass close to the Earth on the night of the 16th. This comet is about a mile across and it moves in an orbit that takes it from close to the Earth to out beyond Jupiter.
This comet comes and goes every five years and it is well known, but this year it will make a close approach to the Earth at only 30 times the distance of the Moon or about seven million miles away.
This is very near in astronomical terms and serves to underline just how real the danger of cosmic impacts on the Earth are.
On the night of the 16th, the comet will be close to the small but bright cluster of the Pleiades, or Seven Sisters, and should appear as a round smudge of fuzzy light about the size of a fingernail at arm’s length. With good binoculars, it may be seen to have a bluish green colour and a short tail.
Comet 46P/Wirtanen will be close to the bright star Capella on Christmas night and it would be seen high up in the northeast in the constellation of Auriga.
The Moon is new on the 7th, first quarter on the 15th, full on the 22nd and last quarter on December 29.
By Clive Jackson
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Clive Jackson is the Director of the Camera Obscura (next to the Castle in Tavira), specialising in education and public outreach.
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To see the December Sky Map click on the pdf link below
PDF Link: ar-algarve-skies-2018-12-december