Leonid meteor shower at a glance
| Detail | Value |
|---|---|
| Activity window | about November 6 to November 30 |
| Peak | around November 17 |
| Zenithal hourly rate (ZHR) | about 15 in normal years |
| Radiant | Leo, in the Sickle |
| Parent body | comet 55P/Tempel–Tuttle |
| Entry speed | about 71 km/s |
These values follow the International Meteor Organization (IMO) calendar. For the full list of showers, see the meteor shower calendar.
Storms that changed astronomy
The Leonids are best known for their storms. On the night of November 12–13, 1833, observers in North America saw meteors falling like snow, with estimates of many thousands per hour. That event led scientists to study meteor showers seriously and to realize that the meteors come from a single point in the sky, the radiant.
Another great storm occurred in 1966, when observers in the western United States reported rates of thousands per minute for a short time. Strong displays also took place between 1999 and 2002, with peaks in the thousands per hour in some places.
Why Leonid storms come and go
The parent comet, 55P/Tempel–Tuttle, orbits the Sun about every 33 years. It last passed through the inner solar system in 1998. Each passage leaves a fresh trail of dust. For a few years around the comet’s return, Earth may pass through one of those dense, young trails, and rates can jump dramatically. In between, the shower settles to a modest 10 to 20 meteors an hour.
Since the debris trails are shaped by the gravity of the planets, especially Jupiter, not every return produces a storm. Modern models compute the trails’ positions, which allowed fairly accurate forecasts of the 1999 to 2002 displays.
The fastest meteors
Leonid particles meet Earth almost head-on at about 71 km per second, close to the maximum possible speed for objects orbiting the Sun. They are often bright, with a greenish or bluish tint, and many leave persistent trains that glow for seconds after the meteor fades.
Where and when to look
The radiant lies in the Sickle of Leo, a backward question-mark pattern of stars that forms the lion’s head. Leo rises around midnight in mid-November, so the hours from about midnight until dawn are best, with the radiant climbing higher as the night goes on.
Do not stare only at the radiant. Meteors appear all over the sky. Looking somewhat away from it gives you longer trails.
Moonlight
With normal rates of around 15 per hour, a bright Moon can hide most Leonids. Check the moon phases for mid-November and the local moonrise and moonset times. If the Moon sets before the radiant is high, you may still have a good dark window before dawn.
Viewing tips
- Go out after midnight. The radiant needs to rise before you see many meteors.
- Choose a dark spot. Faint meteors make up most of a normal Leonid shower.
- Dress warmly. November nights are cold in much of the Northern Hemisphere.
- Be patient. Allow at least an hour; rates rise toward dawn.
- Keep your eyes, not binoculars, on the sky. A wide field of view is what counts.
- Look for trains. After a bright Leonid, watch the same spot for a lingering glow.
For more of what is above the horizon on a given night, see the sky tonight.