The Leonids meteor shower
Key facts
- Peak
- around 17–18 November
- Active
- about 6–30 November
- Rate at peak (ZHR)
- about 15 in most years; storms of thousands per hour in rare years
- Speed
- 71 km/s
- Radiant
- Leo (in the Sickle)
- Parent body
- Comet 55P/Tempel–Tuttle
Dates shift slightly from year to year. This year's peak is in the events calendar.
No shower has shaped the science of meteors more than the Leonids. In most years they are modest, but every 33 years or so they have produced some of the greatest meteor storms ever seen, and one of those storms launched the scientific study of meteors.
The great storms. In November 1799 the German explorer Alexander von Humboldt, travelling in what is now Venezuela, described a sky full of meteors. On the night of 12–13 November 1833 an even greater storm struck eastern North America. Observers described meteors falling like snowflakes, and many people were terrified, thinking the world was ending. The American astronomer Denison Olmsted collected eyewitness reports and noticed that the meteors all seemed to come from one point in the constellation of Leo. This was a key insight: it showed that meteors are particles travelling together through space, not something that forms in the atmosphere.
Further storms followed in 1866 and, most dramatically, in 1966, when observers in the western United States saw meteors at a rate estimated at many tens of thousands an hour for a short time. Then, in 1999, 2001 and 2002, the Leonids produced storms with rates of a few thousand an hour, seen in Europe, North America and Asia.
The parent comet. The Leonids come from Comet 55P/Tempel–Tuttle, discovered independently by Wilhelm Tempel in December 1865 and Horace Tuttle in January 1866. It orbits the Sun about every 33 years, which is why the storms come on roughly that cycle. Each time the comet passes the Sun it lays down a new, narrow trail of dust. Storms happen when the Earth crosses one of these young, dense trails. In the 1990s astronomers, notably David Asher and Robert McNaught, modelled individual trails and predicted the timing of these storms with remarkable accuracy.
The comet last passed the Sun in 1998 and will return around 2031. Current models suggest the years around its next return may bring enhanced activity, but the Earth is not expected to pass through a dense enough trail for a storm on the scale of 1966 for several decades.
What to expect. In an ordinary year, expect 10 to 15 meteors an hour under dark skies before dawn. Leonids are the fastest of all major shower meteors, hitting the atmosphere at about 71 km/s. That speed makes many of them bright, often with a greenish or bluish tint, and they frequently leave glowing trains that can persist for several seconds.
Viewing from the UK. The UK is well placed. Leo rises in the east around midnight in November, so the Leonids are a shower for the early hours. The best time is from about 2 a.m. until dawn twilight, when the radiant is high in the south-east. Look for the Sickle, a backwards question mark of stars that forms Leo's head and mane.
Viewing worldwide. The radiant lies north of the celestial equator but can be seen from almost everywhere, so the Leonids can be enjoyed in both hemispheres. Southern observers see the radiant lower in the north-east before dawn, with somewhat fewer meteors.
Peak dates shift slightly year to year, and enhanced activity depends on the comet's dust trails, so check current forecasts.
Viewing tips
- Watch in the early hours, from about 2 a.m. until dawn, when Leo is high.
- Find the Sickle of Leo, a backwards question mark of stars, to locate the radiant.
- Watch for very fast meteors that leave long-lasting glowing trains.
- Check forecasts in case enhanced activity is predicted for your year.
- Wrap up warmly, because mid-November pre-dawn hours are cold.
Read about the parent: Comet Tempel–Tuttle, and the other comets behind meteor showers.