 Comet Ikeya–Zhang photographed by Philipp Salzgeber on 1 April 2002 | |
| Discovery | |
|---|---|
| Discovered by | Kaoru Ikeya Zhang Daqing |
| Discovery date | 1 February 2002 |
| Designations | |
| Orbital characteristics[6] | |
| Epoch | 8 May 2002 (JD 2452402.5) |
| Observation arc | 341–1,125 years |
| Earliestprecovery date | February 877[1] 3 February 1661[5] |
| Number of observations | 1,893 |
| Aphelion | 101.73 AU |
| Perihelion | 0.507 AU |
| Semi-major axis | 51.119 AU |
| Eccentricity | 0.99008 |
| Orbital period | 365.49 years |
| Max.orbital speed | 59 km/s (2002-03-18) |
| Min.orbital speed | 0.29 km/s[a] (2182-Nov-24) |
| Inclination | 28.121° |
| 93.369° | |
| Argument of periapsis | 34.668° |
| Mean anomaly | 0.135° |
| Last perihelion | 18 March 2002[6][7] 29 January 1661[8] |
| Next perihelion | 1 September 2362[8] 14 March 2363[9] |
| TJupiter | 0.879 |
| EarthMOID | 0.332 AU |
| JupiterMOID | 0.011 AU |
| Physical characteristics[6] | |
Mean diameter | 5.09 km (3.16 mi)[10] |
| 1.48±0.2 days[11] | |
| Comet total magnitude (M1) | 4.0 |
| 2.9 (2002 apparition) | |
Comet Ikeya–Zhang (Japanese, Chinese: 池谷-張彗星, officially designated153P/Ikeya–Zhang) is along-period comet discovered independently by two astronomers fromJapan andChina in 2002. It has by far the longest orbital period of thenumbered periodic comets. It was last observed in October 2002 when it was about 3.3 AU (490 million km) from the Sun.[6]
On 1 February 2002, Chinese astronomerZhang Daqing fromKaifeng discovered a new comet in theconstellationCetus, and reported it to theIAU. He found that Japanese astronomerKaoru Ikeya had discovered it earlier than he had, as the time of sunset is earlier than China. According to tradition, since they discovered the new comet independently, the comet was named after both of them. The comet was initially designated asC/2002 C1 (Ikeya–Zhang).
The comet was observed in 1661, 341 years earlier, by Polish astronomerJohannes Hevelius.[12][5] A bright comet had also been recorded by Chinese astronomers in 1661.[5] Further research byIchiro Hasegawa andShuichi Nakano concluded that historical comets recorded in A.D. 877[2] and 1273[3] were likely previous apparitions of Ikeya–Zhang as well.[1]
The permanent designation "153P" was given to the comet. It has the longest known orbital period of anyperiodic comet (366.51 years). Itsorbital speed around the Sun varies from 59 km/s (37 mi/s) atperihelion to 0.29 km/s (0.18 mi/s) at aphelion.[a]
The comet passed perihelion on 18 March 2002, and withapparent magnitude 2.9. With a multi-hundred year orbit involving asymmetric outgassing the next perihelion passage is expected between 2362–2363. During March–April 2002, protons from the comet tail may have been detected by theCassini–Huygens spacecraft. This data suggested the comet tail had a length greater than 7.5 AU (1.12 billion km), making it the longest yet detected.[13]
| Numbered comets | ||
|---|---|---|
| Previous 152P/Helin-Lawrence | 153P/Ikeya–Zhang | Next 154P/Brewington |
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