 Comet IRAS–Araki–Alcock photographed by Russell E. Milton on 11 May 1983 | |
| Discovery[1][2] | |
|---|---|
| Discovered by | IRAS George E. D. Alcock Genichi Araki |
| Discovery date | 25 April 1983 |
| Designations | |
| 1983d[3] 1983 VII | |
| Orbital characteristics[4] | |
| Epoch | 13 May 1983 (JD 2445467.5) |
| Observation arc | 160 days |
| Number of observations | 347 |
| Aphelion | 195.08 AU |
| Perihelion | 0.9913 AU |
| Semi-major axis | 98.034 AU |
| Eccentricity | 0.98989 |
| Orbital period | 970.49 years |
| Inclination | 73.251° |
| 49.102° | |
| Argument of periapsis | 192.85° |
| Last perihelion | 21 May 1983 |
| TJupiter | 0.408 |
| EarthMOID | 0.0058 AU |
| JupiterMOID | 3.0838 AU |
| Physical characteristics[4][5] | |
| Dimensions | 9.2 km (5.7 mi) |
| 51.3±0.3 hours | |
| 0.02 | |
| Comet total magnitude (M1) | 12.6 |
| 3–4 (1983 apparition) | |
Comet IRAS–Araki–Alcock (formal designationC/1983 H1, formerly1983 VII) is a long-periodcomet that, in 1983, made the closest known approach to Earth of any comet in the last 200 years, at a distance of about 0.0312 AU (4.67 million km; 2.90 million mi).[3]
The comet was named after its discoverers – theInfrared Astronomical Satellite and two amateurastronomers,George Alcock of theUnited Kingdom and Genichi Araki ofJapan. Both men were schoolteachers by profession, although Alcock was retired. Alcock had made his discovery simply by observing through the window of his home, usingbinoculars.[6][7] During the closest approach, the comet appeared as a circular cloud about the size of the full moon, having no discernible tail, and shining at a naked eyemagnitude of 3–4. It swept across the sky at an angular speed of about 30 degrees per day. On May 11 the comet was detected on radar byArecibo Observatory andGoldstone Solar System Radar making it the first comet detected by two different radar systems.[8] A second detection was made by Goldstone on 14 May.[8]
It is a long-period comet, with an orbital period of about 970 years,[4] and is the parent comet of the minorEta Lyridmeteor shower.[9] This shower'sradiant lies betweenVega andCygnus and produces 1 or 2 meteors an hour in mid-May with a peak between 9 May and 11 May.
Comet IRAS–Araki–Alcock made its closest approach to Earth in 1983, at a distance of about 0.0312 AU (4.67 million km; 2.90 million mi). It was the closest approach up to that time of any comet in the last 200 years; onlyLexell's Comet (1770) and55P/Tempel–Tuttle (1366) are thought to have come closer.[4][10] Subsequently, on 12 June 1999, the small cometP/1999 J6 (SOHO) passed about 0.012 AU (1.8 million km; 1.1 million mi) from Earth.[11] What was thought to be a small fragment of252P/LINEAR,460P/PANSTARRS, passed at a distance of 0.0237 AU (3.55 million km; 2.20 million mi) on 22 March 2016.[12]
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