A picture will often illustrate information much better than will a wordy description and this is certainly the case for the image below which shows the locations of night time meteor shower radiants throughout the year and colour-codes each radiant according to the speed of the meteors involved.
This impressive plot, which is based on video data up to the end of 2014, was produced by Jakub Koukal, who coordinates the EDMOND database (European viDeo MeteOr Network Database – see later for a list of participating groups) and was forwarded on by SPA member Richard Fleet, who contributes data as part of the UKMON network. Most of the data has been provided by amateurs.
The plot starts at 12 hours Right Ascension on the right, with Right Ascension then increasing to 24 hours / 0 hours in the centre and finally up to 12 hours at the left. Each dot represents the radiant determined for a particular meteor. With little data being available from the southern hemisphere, there are consequentially few radiants marked at high southerly declinations.
Radiants for the faster meteors are in red, purple and blue, with radiants of slower meteors being marked in yellow and green.
The most distinctive feature is a curve starting at the right which initially dips down before rising again across the centre before starting to dip down against towards the left. You would probably not be surprised to discover that this largely follows the plane of the ecliptic. Within this curve, you can spot several ecliptic meteor showers – the Alpha Capricornids (speed 23 km/s) of July-August are in pale green to the right of centre, with the Delta Aquarids (yellow, 41 km/s) of July-August near the centre ; the early autumn’s northern and southern Taurids (green, 29 km/s) are further to the left. December’s Geminids (green, 35 km/s) are to the left of the Taurids and are slightly displaced above the curve. To their left, November’s Leonids (blue, 71 km/s) can just be made out. The Orionids (66 km/s) can be a bit difficult to spot in the colour scheme but are the purple patch below the Geminids.
The differing colours contrast the high speeds of Leonid meteors (blue) with the slower Alpha Capricornids (pale green).
The large red patch above centre is due to August’s Perseids – another meteor shower that produces fast moving (59 km/s) meteors. Towards the right we can also see January’s Quadrantids (yellow, 41 km/s) and the April’s Lyrids (yellow-orange, 49 km/s). The yellow streak below the Geminids is due to the Monocerotids (42 km/s), with the red streak to its left being due to the Hydrids (58 km/s) – two meteors showers that are active during the long December nights and which are rich in faint meteors.
There are also hints of other radiants. As more data becomes available, these should become more clearly defined.
It can be easy to make the mistaken impression that the showers appear in chronological order from right to left. However, closer inspection shows that some radiants, in particular those of the Quadrantids of January and the Leonids of November are clearly well out of place from where they would appear in a chronological progression.
The groups that contributed to the plot were:
IMO VMDB (International Meteor Organization Video Meteor DataBase)
BRAMON (BRAzilian MeteOr Network)
B OAM (Base des Observateurs Amateurs de Météores)
BOSNET (BOSnian NETwork)
CEMeNt (Central European Meteor Network
CMN (Croatian Meteor Network)
FMA (Fachgruppe Meteorastronomie)
HMN (Hungarian Meteor Network)
IMTN (Italian Meteor and TLE Network)
PFN (Polish Fireball Network)
SVMN (Slovak Video Meteor Network)
UKMON (UK Meteor Observation Network)
MeteorsUA (Meteors UkrAinian)