Geminids – the best meteor shower of the year – marred in 2019 by a full Moon in Gemini around the peak
|Main Activity Dates||Dec 7 – 16|
|Peak Rates||Dec 14d 12h UT|
|Best Observed Rates||Early morning of 14 Dec|
|Visibility each night (UK)||Visible all night|
|Moonlight issues at Maximum||Major – nearly full Moon|
One shower dominates meteor observing in December and that is the Geminids which, at their peak, produce higher observed rates than do the Perseids of August. Most of the Geminid activity occurs between Dec 7 and Dec 16, although some outliers can be detected as early as Dec 4 and as late as Dec 17.
Observing the Geminids does however pose the challenges of enduring the cold December nights and of a (usually) lower chance of clear skies than for the Perseids. The meteor section director avoids the cold by using video cameras to watch for him and analysing the data in the warm!
In some ways the Geminids are like the Perseids, being rich in bright meteors. In other ways they are different, with very few Geminids leaving persistent trains – a consequence of the Geminids are more robust particles derived from asteroid 3200 Phaethon whereas the Perseids are more fragile icy material derived from comet Swift-Tuttle.
Good Geminid rates can be seen for around two nights around their peak, but drop away very quickly after the maximum. The Geminids are observable throughout the night, with the best observed rates usually between 01h and 03h UT, when the radiant is highest in the sky. The 2019 peak is due during daylight in the UK on Dec 14, most likely within an hour or two of 12h UT. The peak is quite broad, however, and so observed rates should be rather good from late evening onwards on Dec 13 and will probably also be quite good during Dec 14-15 . By the night of Dec 15–16, however, they are likely to have dropped off markedly.
Given the unreliable December weather, however, it is best to make use of any clear sky rather than simply focus on the maximum night. Moonlight will also be a major issue this year, with a nearly-full Moon in Gemini on the 13th.
Below is a chart showing the location of the Geminid radiant: