A regular highlight of December is the peak of the annual Geminid meteor shower. This is arguably the best shower of the year because it has a high ZHR (Zenithal Hourly Rate) of 120 meteors per hour, reliably showing a good number of meteors.
December nights are long and dark, making them perfect for meteor watching.
Find out more about meteor showers
Contrast this with the popular summer shower, the Perseids, which has just four hours of true darkness as experienced from the centre of the UK.
Geminids peak night is 13/14 December when around 12 hours of true darkness (18:00–06:00 UT) can be experienced.
Admittedly, these are at lower temperatures than you’d experience when observing the Perseids.
Zenithal hourly rate explained
The zenithal hourly rate, or ZHR, of a meteor shower is the total number of meteors you might expect to see during peak activity with absolutely perfect conditions, i.e. under clear, dark skies away from light pollution.
The ZHR is often quoted during big meteor showers; however, given the above caveats, observers should expect the actual number to be somewhat lower.
In 2019 the Geminid peak is compromised by a bright, just past full Moon. This rises at 17:10 UT on 14 December and hinders the number of visible meteors seen.
In contrast, the annual Ursid shower peaks on the night of 22/23 December when the 10%-lit waning crescent Moon rises at 05:00 UT on the 23rd.
Although the ZHR for the Ursids is just 10 meteors per hour, the fact that it peaks under dark sky conditions will make it a better prospect.
A waning crescent Moon will help with observing the Ursid meteor shower. Credit: BBC Sky at Night Magazine
What are the Geminids and how can I spot one?
BBC Sky at Night Magazine’s Elizabeth Pearson reveals all you need to know
Meteor showers usually occur when Earth passes through the trail of debris left by a comet.
The Geminids are unusual, however, in that the trail of debris was left behind by an asteroid, 3200 Phaethon.
Meteor showers are one of the easiest astronomical events to observe as they are best seen with the naked eye making it the perfect opportunity to get both children and adult beginners excited about astronomy.
Find a place that is dark and away from light pollution, such as a location away from towns and cities, provided it is safe to do so.
If you are lucky enough to live under very dark skies and can observe from the comfort of your own garden, turn off the lights in your house so they don’t spoil the view.
Avoid using lights such as torches and mobile phones as this will spoil your dark adapted vision.
If you need to see in the dark, use a red torch. If you need to look at your mobile phone, you may be able to turn your screen red in the settings.
It will take around 20 minutes for your eyes to dark adapt, but hopefully after a little wait you should start to see meteors shooting across the sky.
Remember: clear nights are cold nights. You will be sitting still for a long time, so wrap up warm, bring something to eat and perhaps a hot drink as well.
How do I find the Geminids?
The radiant of the Geminids is just beside the bright star Castor. Credit: Pete Lawrence
The area of the sky from which a meteor shower appears to originate is known as the ‘radiant’.
The Geminids are so-called because they seem to radiate out from the constellation of Gemini.
To find Gemini, imagine a line between Orion’s right foot (Rigel) and left shoulder (Betelgeuse), then follow that line on for around the distance between your thumb and little finger stretched out at arm’s length.
There should be a pair of bright stars here: Castor and Pollux, the ‘heads’ of Gemini’s twins.
The radiant is just by Castor, but you want to look slightly away from this region rather than directly at it. If you spot a meteor coming from this region, you’ve seen a Geminid.