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Geminids meteor shower reaches maximum this week
BY MARK ARMSTRONG
ASTRONOMY NOW

Posted: 11 December 2012


The Geminids meteor shower is the richest shower of the year and along with the much lesser Ursids nicely rounds off the meteor observing season for 2012. With normal limits of Dec 8-17, the maximum is predicted for the 7pm on the night of 13/14 December. The Moon, amazingly, is new on 13 December, leaving observers free of the all too often blight of moonlight drowning out the fainter meteors.


The Geminids meteor shower peaks on the night of 13/14 December. The radiant lies close to Castor. AN graphic by Greg Smye-Rumsby
 
In good conditions the Geminids regularly produce 80 meteors per hour (ZHR 100+) with the radiant, which lies a few degrees north of Castor, highest in the south (67 degrees) at 1am. Geminids are relatively slow meteors entering the upper atmosphere at speeds of 35km/s and there are a large proportion of bright, colourful events. The meteoroid stream has spawned from an asteroid - (3200) Phaethon- rather than a comet and this seems to make the debris more solid or robust and can survive for longer before burning up. It's worth observing on the following night, 14/15 December too, as observations tend to suggest many of the brighter events occur some hours after maximum so it's possible the tail-end of this could be observed.

The Ursids are active between 17-25 December with the peak occurring on 22-23 December with low rates of at around five meteors per hour. The radiant lies close to the 'bowl' of Ursa Minor in the vicinity of Polaris, the Pole Star, and is circumpolar from the UK. The debris stream has been shed by the Ursids parent comet 8P/Tuttle. This time the waning gibbous Moon will interfere with observations attempted around midnight but will be out of the way by 3am when the radiant is climbing.

As with observing any meteor shower the best advice is not to stare at the actual radiant but at an altitude of 50 degrees (about the same altitude of the Pole Star from the UK) and 30-40 degrees to one side of shower radiant (the width of a fist held at arm's length is about ten degrees).

Recent nights have been bone-chilling so be well prepared, especially if you are travelling to a dark site to make your watch. Wrap up well in layers of warm, dry clothing and keeping hands, feet and head warm is essential! Many people just prefer to observe for fun but if you would like to 'do some science', then check out the advise on the British Astronomical Association's website.