Comet Thatcher
The comet behind the April Lyrids, the oldest meteor shower on record.
Key facts
- Designation
- C/1861 G1 (Thatcher)
- Type
- Long-period comet
- Orbital period
- about 415 to 420 years
- Closest to the Sun
- 0.92 AU (about 138 million km)
- Farthest from the Sun
- about 110 AU, far beyond Pluto
- Tilt of orbit
- about 80°, almost at right angles to the planets
- Nucleus
- not measured
- Discovered
- by A. E. Thatcher, an amateur astronomer in New York, on 5 April 1861
- Returns
- passed perihelion on 3 June 1861; next due around 2280
Orbit
Comet Thatcher swings round the Sun once every four centuries or so. Its orbit is tilted almost upright to the planets and reaches out about 110 times Earth's distance from the Sun. Dust shed along this path meets Earth each April at about 49 km/s.
Size and nature
The comet was seen only in 1861, before photography of comets, so its nucleus has never been measured. It reached about third magnitude, visible without a telescope from dark places. Because its period is so long, it is a long-period comet, one of the class that comes from the far edge of the Solar System and spends most of its life in the cold.
History
A. E. Thatcher, an amateur observer in New York, found the comet in April 1861; others saw it independently within days. Its orbit was soon worked out, and in 1867 the German astronomer Edmund Weiss showed that the April Lyrid meteors move along it. The Lyrids themselves have a far longer history: Chinese records describe a shower in 687 BC in which 'stars fell like rain', thought to be the earliest written account of any meteor shower.
Meteor showers
The Lyrids peak around 22 April, with typically 10 to 20 meteors an hour under dark skies. They are fast and fairly bright, and some leave glowing trains. Now and then Earth meets a denser clump of older dust and the rate jumps; outbursts of around 100 an hour were seen in 1982 in the United States, and Japan recorded a strong display in 1945.
Its meteor showers
- The Lyrids peak around 22–23 April; about 18 (occasional outbursts near 100) an hour at best; 49 km/s
Key dates
| Date | What happened |
|---|---|
| 5 April 1861 | A. E. Thatcher discovered the comet behind the Lyrid meteors. |
| 3 June 1861 | Comet Thatcher passed closest to the Sun; it will not return until about 2280. |
Did you know?
The Lyrids have been watched for at least 2,700 years.
Comet Thatcher's last visit came just as the American Civil War began.
Lyrid outbursts cannot yet be predicted as precisely as Leonid storms.