Welcome to the December night sky and to the cold dark nights of the winter solstice. This year the Sun is at its lowest point in the heavens on the 21st, and therefore it will be the longest night of the year.
The bright planet Venus is still visible low in the south-west at sunset and, as the month progresses, it moves slowly up into the constellation of Aquarius and closer to the red planet Mars. The thin crescent moon is between the pair on the evening of the 4th.
The grand constellation of Orion, the Hunter, can now be seen rising in the East at Sunset and an hour later, when it is fully dark, the brightest star in the night-sky rises in the south-east. This is Sirius and it is one of the closest stars to our solar system at about nine light years away.
Sirius is 25 times brighter than the Sun and is hotter, causing it to shine with a brilliant white colour; and because it is low down in the sky during December evenings, our turbulent atmosphere will cause the white light of Sirius to flash and twinkle all the colours of the rainbow. This often leads people to mistake Sirius for the Christmas star, or the star of Bethlehem, and it certainly looks the part when it sparkles in the night-sky on a cold frosty evening in December.
The night of the 13th, and on into the morning of the 14th, is the peak of the normally strong Geminid meteor shower. Unfortunately this year it coincides with a full Moon, and not just any old full moon, but a Supermoon. What this in fact means is when the Moon is at its closest point in its orbit to the Earth, it will appear to be slightly bigger and brighter than normal. This has happened three times in 2016, so it’s not that rare.
The full Moon of October, November and December all qualify as Supermoons with the full Moon of November being slightly the largest of the three.
The other notable meteor shower in December is the Ursids that occurs on the night of the 22nd. This shower is dust from the tail of Comet Tuttle, unlike the Geminids that are dust from a minor planet or Asteroid called Icarus.
The Ursids can be seen coming from the direction of the constellation of Ursa Minor, or the Little Bear close to the Pole Star.
The Moon is at first quarter on the 7th, full on the 14th, last quarter on the 21st and new Moon again 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