On New Year’s day, Comet Tuttle will be closest to the Earth, a mere 25 million miles away, and also at its brightest. The comet will just be visible to the unaided eye, so you will need to be observing from a very dark site.
A gallery of images, and sky maps of when and where to look, can be found at SpaceWeather.com.
[Image of Comet Tuttle taken by Pete Lawrence]
Happy solstice to all our readers!
The winter solstice this year occurs at 6am, on 22 December, 2007.
That is the time when the Earth’s North pole is pointing directly away from the Sun (which is why it is so much colder in the Northern hemisphere).
For people living in the Southern hemisphere, the South pole is pointing towards the Sun, making it summertime ‘down-under’!
On the night of the 13 December, and the morning of the 14 December, the Geminid shooting star shower reaches its peak.
The Earth will be ploughing through a stream of debris left behind by asteroid Phaethon, and we see these fragments burn up as they hit the Earth’s atmosphere, causing the shooting stars.
And they are often big fragments! I myself saw a huge fireball in the UK during the Geminid shower of 1994.
More details can be found at the NASA science website.
Details of all the major annual meteor showers visible from the UK are available on the NMM website.
Comet Holmes now appears almost twice the diameter of the full Moon in the night sky.
To see the latest images, see the gallery at Spaceweather.com.
Because the comet is so large in the sky, it is spread out, making it appear much fainter in the night sky. But it is still visible to the unaided eye when well away from light pollution.
The best way to observe the comet now is with a pair of binoculars that are large (to collect a lot of light) but with low magnification (because the comet is so large in the sky).
The apparent size and brightness of Comet Holmes is regularly estimated by amateur astronomers world wide. A list of estimates is available at the IAC/ICQ/MPC website. Using averages of these estimates, I have plotted the apparent size of Comet Holmes against time (below).
In this graph, you can see the number of days along the bottom since 24 October, 2007 – the date when Comet Holmes suddenly increased in brightness.
Up the left hand side of the graph, I show the angular size of the comet – that is how big the comet appears to us in the night-time sky. The apparent size of the Full Moon, which is half a degree across (or 32 arc-minutes) is labelled for comparison.
Up the right hand side of the graph, I show the actual size of Comet Holmes in millions of km (assuming that the comet is at a fixed distance of 1.7 AU away – although the comet is moving away from us, it has not moved too much over the last 2 months).
Note how within days of the outburst in October, the comet was bigger than the separation of the Earth and the Moon, and within weeks it was physically bigger than the Sun!
Currently, it appears about 1 degree (60 arc-mins) across in the night sky – that’s twice the diameter of the full Moon. In physical size, the nucleus of the comet is now surrounded by a cloud of gaseous water that is over 2.5 times larger than the Sun.
What an amazing comet!