Like last month, the Moon will be drifting past two planets on its Moonthly orbit around the Earth. Unlike last month, the Moon will be passing by a different pair of planets!
Last month, the Moon drifted past Venus and Jupiter, forming a wonderful smiley face in the evening sky! This unique event was witnessed around the world,and Naveen L Nanjundappa, Vice President of the Bangalore Astronomical Society, took the wonderful photograph below (many more photographs are on the BBC News website, and SpaceWeather.com).
This month, the Moon will be passing by the planets Jupiter and Mercury on the 28th and 29th of December. Their exact alignment and the best time to look will depend on your location, but the three will be close to each other. For the UK, the best time to look is on the evening of the 29th, just after sunset (4.30pm is the best time), low to the South-West, when the crescent Moon is just to the top left of the bright Jupiter, and slightly fainter Mercury.
In fact, for just a brief period after sunset on the 29th, the Moon is so close to Mercury that it actually hides it! (an occultation) Unfortunately, that event will only be visible from a small region of the Pacific Ocean, a few thousand miles East of Japan!
However, for people living in western/central Australia, just after their sunset (which occurs 6 hours later than Eastern Japan), they will get to witness the Moon covering Jupiter instead!
It just goes to show what a difference a few thousand miles can make!
On new year’s eve, the Moon will have moved along to Venus, higher and brighter than both Jupiter and Mercury. To see where the planets will be every night, take a look back at my December’s Dance of the Evening Planets post.
At 12.03pm GMT today, the poles of the Earth were aligned with the Sun, which is what we call the solstice. While in the Northern hemisphere, the North pole was pointing away from the Sun (it was the Winter Solstice), in the Southern hemisphere, the South pole was pointing towards the Sun (the Summer Solstice), which is why it is winter in the North and summer in the South.
The image below shows a stacked series of images taken 20 minutes apart throughout the 17th December, 2005 (within just a couple of days of the winter solstice), showing how the Sun moved across the sky during that day, from the South-East to the South-West. A timelapse movie version is also available, showing that at this time of year, while the Sun is very low in the sky, the full Moon is very high in the sky.
The Winter Solstice also marks the shortest day, although the earliest Sun-set and latest Sun-set occur on different days (the 12th and 30th of December, 2008).
There are lots of special events to mark the solstice, including a gathering at Stonehenge in Wiltshire (see photographs on the BBC News). Under the early Julian Calendar, the winter solstice actually occurred on the 25th of December, but because that calendar was not accurate, the solstice slipped to the 21st (the accuracy of the calendar was corrected with the introduction of the Gregorian calendar in 1582).
However, we still traditionally keep the 25th of December as the day for celebration, and Christmas now includes a rich mix of celebrations, including Roman (Saturnalia, and Dies Natalis Solis Invicti, the birthday of the unconquered sun), Nordic Pagan festivals and the Christian celebration of the birth of Christ (see more about the origin of Christmas at this Wikipedia article).
Whichever way you choose to celebrate this time of year, we hope you will enjoy yourselves and have a very happy festive season!
On Friday the 12th of December, we have the biggest Full Moon for 15 years!
The Moon orbits the Earth in an elliptical (oval-shaped) orbit, and during tonight’s full Moon, it will be closer than usual – only 356,600km away from Greenwich! (which is about 363,000km away from the centre of the Earth).
On average, the Moon is 378,000 km away, and at furthest, it is 399,300 km away from the Earth’s surface. So tonight’s full Moon is 6% closer than average, and so 11% brighter than average! (Or, to put it another way, it is 11% bigger & 20% brighter than when the Moon is at its furthest point away from us).
Today, the 12th of December 2008, we have the earliest sunset of the year in the Northern hemisphere. In Greenwich, the Sun sets at 15:50GMT.
The earliest sunset occurs on a different day to the solstice due to a combination of the Earth’s elliptical (oval-shaped) orbit and it’s tilt. Put together, these two effects are known as the Equation of Time, the difference between what an averaged mechanical clock will say and what a Sun dial will say.