The year's shooting stars

A shooting star is a grain of dust, often no bigger than a grain of sand, that enters the atmosphere at several dozen kilometres per second and burns up. When the Earth passes through the dust left behind by a comet, these streaks of light become numerous and all seem to come from the same point in the sky, the radiant: this is a meteor shower, named after the constellation where its radiant lies.

Calendar of the main showers

The peak dates below are those published every year by the International Meteor Organization; they can shift by a day from year to year. The “zenithal hourly rate” is a theoretical figure: what one observer would see under a perfect sky, with the radiant overhead.

Shower	Peak	Theoretical rate	Parent body
Quadrantids	3–4 January	up to about 80 an hour, very short peak	asteroid 2003 EH1 (probably)
Lyrids	around 22 April	about 18	comet Thatcher
Perseids	12–13 August	about 100	comet 109P/Swift-Tuttle
Orionids	around 21 October	about 20	Halley’s Comet
Leonids	around 17 November	about 15	comet 55P/Tempel-Tuttle
Geminids	13–14 December	about 150	asteroid (3200) Phaethon

The two big dates

The Perseids are the best known, because they fall in high summer, on mild nights. They are sometimes called the “tears of Saint Lawrence”, whose feast is on 10 August.

The Geminids in December are often even richer, but you have to brave the cold. Their radiant, near the star Castor in Gemini, is already high in the evening: it is the easiest shower to see before midnight.

How to watch them

1. Check the Moon first: a gibbous or full Moon washes out the faintest shooting stars. The booking calendar shows the phase for every night.
2. Lie down and take in a wide stretch of sky, not necessarily towards the radiant: the longest trails appear 40 or 50 degrees away from it.
3. Wait for the second half of the night: the radiant climbs and the Earth “faces into” the dust cloud, like a windscreen in the rain.
4. Wrap up: even in August, you cool down fast lying still on the plateau.

In practice you see fewer shooting stars than the theoretical rate: under a good sky, a few dozen an hour for the Perseids is already a very fine night.