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Ikeya–Zhang on April 1, 2002
Discovered byKaoru Ikeya, Zhang Daqing
Discovery dateFebruary 1, 2002
C/2002 C1, C/1661 C1
Orbital characteristics A
EpochOctober 13, 2002
Aphelion101.9200 AU
Perihelion0.507141 AU
Semi-major axis51.2136 AU
Orbital period366.5101 yr[1]
Max. orbital speed59 km/s (2002)
Min. orbital speed0.29 km/s[a]
Last perihelionMarch 18, 2002[1][2]
January 29, 1661[3]
Next perihelionSeptember 1, 2362[3]

Comet Ikeya–Zhang (Japanese, Chinese: 池谷-張彗星, officially designated 153P/Ikeya–Zhang) is a comet discovered independently by two astronomers from Japan and China in 2002.

On February 1, 2002, Chinese astronomer Zhang Daqing from Kaifeng discovered a new comet in the constellation Cetus, and reported it to the IAU. He found that Japanese astronomer Kaoru 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 as C/2002 C1 (Ikeya-Zhang).

The comet was probably observed in 1661, 341 years earlier, by Polish astronomer Johannes Hevelius. A bright comet had also been recorded by Chinese astronomers in 1661.

The permanent designation "153P" was given to the comet. It has the longest known orbital period of any periodic comet (366.51 years). Its orbital speed around the Sun varies from 59 km/s at perihelion to 0.29 km/s at aphelion.[a]

The comet passed perihelion on March 18, 2002, and with apparent magnitude 3.5, it became the brightest comet since 1997.

The orbital paths of three comets, outlined in turquoise, against the orbits of Jupiter, Saturn, Uranus and Neptune, outlined in green
The orbits of three periodic comets, Halley, Borrelly and Ikeya–Zhang, set against the orbits of the outer planets. Ikeya–Zhang is to the right.

See also[edit]


  1. ^ a b v = 42.1219 1/r − 0.5/a, where r is the distance from the Sun, and a is the major semi-axis.


  1. ^ a b "JPL Small-Body Database Browser: 153P/Ikeya-Zhang". Jet Propulsion Laboratory. Retrieved 2011-04-20. 2002-10-02 last obs (arc 341.6 yr)
  2. ^ "153P/Ikeya-Zhang Orbit". Minor Planet Center.
  3. ^ a b Syuichi Nakano (2002-08-13). "153P/Ikeya-Zhang". OAA Computing and Minor Planet Sections. Retrieved 2009-10-04.

External links[edit]

Numbered comets
153P/Ikeya–Zhang Next