153P/Ikeya–Zhang

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. It has by far the longest orbital period of the numbered periodic comets.

153P/Ikeya-Zhang

Ikeya–Zhang on April 1, 2002
Discovery
Discovered by	Kaoru Ikeya, Zhang Daqing
Discovery date	February 1, 2002
Alternative designations	C/2002 C1, C/1661 C1
Orbital characteristics ^A
Epoch	October 13, 2002
Aphelion	101.92 AU
Perihelion	0.50714 AU
Semi-major axis	51.213 AU
Eccentricity	0.99009
Orbital period	366.51 yr[1]
Max. orbital speed	59 km/s (2002)
Min. orbital speed	0.29 km/s[lower-alpha 1] (2182-Nov-24)
Inclination	28.119°
Last perihelion	March 18, 2002[1][2] January 29, 1661[3]
Next perihelion	September 1, 2362[3] 2363-Mar-14[4]

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.[lower-alpha 1]

The comet passed perihelion on March 18, 2002, and with apparent magnitude 3.5, it became the brightest comet since 1997. With a multi-hundred year orbit involving asymmetric outgassing the next perihelion passage is expected between 2362–2363.

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

• Johannes Hevelius
• List of Solar System objects by greatest aphelion

Notes

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

References

1. "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. Syuichi Nakano (2002-08-13). "153P/Ikeya-Zhang". OAA Computing and Minor Planet Sections. Retrieved 2009-10-04.
4. Horizons output. "Observer Table for Comet 153P/Ikeya-Zhang [2002]" (Soln.date: 2020-Jun-17). Retrieved 2020-07-09. (Observer Location:@sun Perihelion occurs when deldot flips from negative to positive)

• Cometography.com: 153P/Ikeya-Zhang

External links

• Orbital simulation from JPL (Java) / Horizons Ephemeris
• 153P/Ikeya-Zhang (2002)