A great year for Geminids

The Geminid meteors (shooting stars) are at their best this December, and with no Moon around to wash out the view, all you have to worry about is the clouds!

Each year around 14 December the Geminid meteors put on a display, and they have come to be regarded as the best meteor shower of the year. While rates of 120 an hour are often quoted, this only applies under ideal conditions, which for most people doesn’t apply. Even so, with typical UK skies you could see one every few minutes – a great free spectacle.

Two meteors
Two Geminid meteors imaged by Bill Ward on 14 December 2012. The meteors radiate away from a point just above Castor, the upper of the two lead stars of Gemini, below centre.

When and where to look

You can see the meteors throughout the night, but the later in the night you observe, the more you’re likely to see. This is because the meteors come from a point in the constellation of Gemini close to the bright star Castor, which is just rising as it gets dark. As the night progresses, this point, known as the radiant, gets higher in the sky so more meteors are visible. It reaches its peak about 3 am on Monday 14 December – which for most people means starting to observe on the night of Sunday 13 December.

There is no preferred place in the UK for seeing Geminids, other than getting away from city lights. The meteors will be equally visible all over the country and indeed Europe, given clear skies.

Bear in mind that meteors appear at random, and that some may be faint, so if after a few minutes of observing you haven’t see any, don’t give up on them. An observing time of at least an hour is needed to get a good chance of seeing a fair number.

Meteors are caused by tiny particles of space dust that collide at high speed with Earth’s upper atmosphere. In the early hours of the morning the Earth is moving directly towards the meteors, so they hit the upper atmosphere at higher speed and glow more brightly. So if you want the best display, be prepared for the long haul and wrap up warm!

Gemini meteors will also be seen for several days before and after the night of maximum, so if there’s a chance of clear skies beforehand don’t pass up on it. However, because the numbers tend to drop quite rapidly after maximum make the most of early opportunities.

When observing, choose a site with as large a view of the sky as possible, and try to exclude any lights from your field of vision. Although the radiant is in the constellation of Gemini, it’s best not to look directly at that part of the sky, which in the evening is rising in the east. The optimum direction is about 40º away from the radiant, and in mid sky.

There are also likely to be meteors occurring with no particular source, known as sporadics. These can occur at all times of the night, adding to the numbers visible. Another meteor shower, known as the Ursids, will be active from 17 to 25 December, with its peak around 22–23 December. These meteors have a radiant near the star Kochab, which is below the Pole Star during December evenings.

The next opportunity to view a meteor shower is in early January, with the annual Quadrantid meteors on January 3–4.

Photographing the meteors

Because meteors appear at random, the only way to photograph them is to open the camera shutter for a time exposure and hope that one passes through the field of view in that time. Fix the camera on a tripod if possible and do some test exposures with the ISO rating (sensitivity) at a high figure, such as 3200 or greater. Focus the camera on infinity (which usually requires manual focus, or a scene setting for night photography) with the lens at its widest aperture (smallest number, such as f/2.8) and give an exposure time of 30 seconds. If the result is too washed out because of light pollution you will need to give shorter exposures. Recent mobile phones may even have a setting for meteor photography.

You’ll need to repeat the exposures many times to stand a chance of recording a meteor. Good luck!

Two Geminids
Two Geminid meteors photographed on 14 December 2017 at 3:05 am during a 20-second exposure from Walmer, Kent by Paul Sutherland.

For more information about the Geminids, and about meteors and how to observe them, go to our meteor section web page about this shower.