The Geminid meteor shower
WHEN: Shower peak is on the night of 13/14 December
The Geminid radiant is close to the bright star Castor – all Geminid trails should point back to this location
THE GEMINID METEOR shower reaches its peak on the night of 13/14 December and the new Moon on the 11th is perfectly timed to give us dark skies. The Geminid shower is arguably the most active of the year, and unlike its more comfortable rival (August tends to be warmer than December) can be watched for the many hours of darkness that make up a long winter’s night.
The shower’s zenithal hourly rate reaches a peak value of 120 meteors per hour. This is predicted to occur at 18:00 UT on 14 December, but the peak tends to be broad. Near maximum, rates should continue for about a day centred on this time. Consequently, the best
night for Geminid watching will be that of 13/14 December with the 14/15 December potentially putting on a decent show as well.
There are other factors that kick in to adjust the zenithal hourly rate. These include radiant altitude, and the time of night your meteor watch takes place. After midnight, the Earth will have turned to encounter the meteoroids that impact on Earth’s atmosphere to produce the meteor trails head on. This raises the energy of impacts and the brightness of the trails that are seen.
The radiant is located close to mag. +1.9 Castor (Alpha (_) Geminorum) in Gemini around the time of peak activity, and this places it at its highest point in the sky, due south, around 02:00 UT.
From the centre of the UK, the radiant reaches a very respectable height of 68º. The radiant’s location near to Castor means that it’s easy to trace a line back to check whether any meteor you’ve
seen is a Geminid. During the peak, a trail must line up with the star in order to be part of the shower.
Geminid meteors impact our atmosphere at a speed of 35km/s – slower than the 59km/s Perseids. Slower meteors are more photogenic because their trails stay on each part of a camera sensor for that bit longer. This means that the Geminids should be an exciting shower to try and photograph too.
The best way to enjoy the Geminids is to place a sunlounger somewhere away from any light interference, lie back and keep looking up. Look to a height around 60º up and in any direction. Meteors will be shortest close to the radiant. For decent trail lengths, a location roughly 60º away from the radiant’s azimuth works well. Do remember to wrap up warm though as December nights can be very cold. The Geminid meteor shower is active from 4-17 December.