29-11-2008 December Night Sky (Article 165)

[Simon Kenny]

December Night Sky (Article 165)

Now that December is upon us, we’re entering years end with the winter solstice occurring on the 21st. On the solstice we have the least amount of daylight hours of the year. The Sun rises at 8.46 in the morning and sets at 16.20. Newgrange in Co Meath was built several thousand years ago and the structure was orientated in such a manner that the first beams of the Sun light on the day of the solstice pour down through a hatch above the door illuminating the inner chambers, what is not widely known is that due to a 26 thousand year wobble in the Earth’s orbit, the Sun’s position at sunrise has shifted over the millennia and does not illuminate the chamber to the same degree as the original builders had intended.
On December the 1st, if you look towards the west in the evening before 5pm, you will the crescent Moon and a very bright star only 4 degrees away (2 moon diameters). This bright star is in fact the planet Jupiter. After 5pm you will notice a second even brighter star appearing to the lower left of the Moon, this is the planet Venus. The Moon passes over Venus between 3.32pm and 5.05pm; this should be visible in daytime if the sky is clear. The close proximity of any 2 planets or the Moon is called a conjunction; this one is particularly good as it isn’t often that the Moon passes over a bright planet. First quarter Moon is on the 5th, full Moon is on the 12th, last quarter is on the 16th and new Moon is on the 27th.
The planet Saturn is visible in the early morning sky as a bright star in the constellation Leo, one very interesting point to note is that the planets rings are closing fast, and on Christmas morning the rings will be almost edge on making for a very rare view of it through a telescope. Don’t worry if you don’t catch it on that morning as seeing it several days before or after Christmas day will show the same view. After the 25th, the rings begin to slowly widen again thus making them easier to see.
The winter constellations are at their prime this month, constellations such as Orion, Taurus, Gemini, Auriga, Andromeda, Cassiopeia, Perseus and Canis Major are all visible. A good star atlas will show their locations in the sky, the internet is also a great guide for showing the locations of these constellation. Explaining the constellations is so much easier with a computer planetarium program such as the one we use at the club meetings, so come along to the December club meeting where we will explain how to find the various constellations.
This month’s club meeting is in room 207 in Mary Immaculate College in Limerick on Wednesday the 3rd at 8pm. Our main speaker is club member John O’Mahony and he will be talking about “Einstein and the Universe”.