Comet IRAS–Araki–Alcock
The comet that passed closer to Earth in 1983 than any other for two centuries, and the parent of the Eta Lyrids.
Key facts
- Designation
- C/1983 H1 (IRAS–Araki–Alcock)
- Type
- Long-period comet
- Orbital period
- about 970 years
- Closest to the Sun
- about 0.99 AU (about 148 million km)
- Farthest from the Sun
- about 195 AU
- Tilt of orbit
- about 73°
- Nucleus
- about 9 km across, measured by radar
- Discovered
- by the IRAS satellite and by the amateurs Genichi Araki and George Alcock in April and May 1983
- Returns
- passed closest to Earth on 11 May 1983
Orbit
The comet takes nearly a thousand years to orbit the Sun. In May 1983 it passed 4.7 million km from Earth, about 12 times the distance of the Moon, the closest pass of any comet since 1770. It raced across the sky, moving by about 30 degrees a day at its closest.
Size and nature
The giant radio dishes at Arecibo and Goldstone bounced radar signals off it, the first time two radar systems had detected a comet. The echoes showed a nucleus about 9 km across surrounded by a cloud of larger grains. Its tail was short, and its coma, spread over a huge patch of sky because it was so close, looked like a faint glowing ball.
History
The Infrared Astronomical Satellite, a British, Dutch and American space telescope, detected it in April 1983. The Japanese schoolteacher Genichi Araki and the English schoolteacher George Alcock, who looked for comets with binoculars, found it independently in early May. Alcock spotted it from his home, looking through a window.
Meteor showers
The Eta Lyrids are a faint shower in May, peaking around 9 to 11 May with one or two meteors an hour. Camera networks recording meteor orbits showed in the 2000s that they follow the comet's orbit. They are a good example of how modern networks find showers too faint for the eye.
Its meteor showers
- The Eta Lyrids peak around 9–11 May; about 3 an hour at best; 43 km/s
Key dates
| Date | What happened |
|---|---|
| 3 May 1983 | George Alcock spotted the comet now called IRAS–Araki–Alcock with binoculars. |
| 11 May 1983 | Comet IRAS–Araki–Alcock passed 4.7 million km from Earth, the closest comet in two centuries. |
Did you know?
George Alcock found five comets and five novae, all with binoculars, from England.
The 1983 pass was the closest of any comet to Earth since Lexell's Comet in 1770.
The comet was named after a satellite as well as two people.