Comet Tempel–Tuttle
The small comet behind the Leonids, whose dust trails have produced the greatest meteor storms ever seen.
Key facts
- Designation
- 55P/Tempel–Tuttle
- Type
- Halley-type comet
- Orbital period
- about 33 years
- Closest to the Sun
- 0.98 AU (about 146 million km), just inside Earth's orbit
- Farthest from the Sun
- about 19.7 AU, near the orbit of Uranus
- Tilt of orbit
- 162° (retrograde)
- Nucleus
- about 3.6 km across
- Discovered
- by Wilhelm Tempel on 19 December 1865 and Horace Tuttle on 6 January 1866
- Returns
- last at perihelion 28 February 1998; next May 2031
Orbit
Tempel–Tuttle circles the Sun every 33 years on an orbit that reaches out to near Uranus. It travels backwards relative to the planets, so Leonid meteors hit the atmosphere at about 71 km/s, close to the fastest possible speed for anything bound to the Sun. Such speed makes them bright, often green, and quick to leave glowing trails.
Size and nature
The nucleus is small, about 3.6 km across, and only modestly active. Its dust matters far more than its size. Each pass lays a fresh, narrow trail of grains along the orbit. The trails stay compact for centuries, so when Earth runs straight through a young one, thousands of meteors can fall in an hour.
History
The Leonid storm of November 1833 was seen across North America, with meteors falling 'like snowflakes'. The American astronomer Denison Olmsted noticed that they all came from one point in the sky in Leo and argued that Earth had met a cloud of particles in space. Hubert Newton of Yale traced records back a thousand years and predicted a return in 1866, which duly came. Wilhelm Tempel and Horace Tuttle had found the comet itself just before, in 1865–66, and its orbit matched the meteors. In 1966 observers in the western United States counted Leonids at rates estimated at tens of thousands an hour.
Meteor showers
The Leonids return every November. In most years they are modest, but for a few years either side of the comet's return they can rise to an outburst or storm. Around the comet's 1998 return, astronomers learned to calculate where individual trails lay, and the storms of 1999, 2001 and 2002 arrived within minutes of the predicted times.
Its meteor showers
- The Leonids peak around 17–18 November; about 15 in most years; storms of thousands per hour in rare years an hour at best; 71 km/s
Key dates
| Date | What happened |
|---|---|
| 19 December 1865 | Wilhelm Tempel discovered the comet now called Tempel–Tuttle. |
| 6 January 1866 | Horace Tuttle independently found Comet Tempel–Tuttle. |
| 28 February 1998 | Comet Tempel–Tuttle passed closest to the Sun. |
Did you know?
The 1833 storm turned the study of meteors into a science almost overnight.
Leonid trails are named by the year the comet shed them, such as the 1899 trail behind the 1999 storm over Europe.
The comet's next return in 2031 may bring stronger Leonids, but calculations do not promise a full storm.