Comet 22P Kopff.jpg
14" reflector imaged on 2009-06-27
Discovered byAugust Kopff
Discovery dateAugust 23, 1906
1906 Q1, 1919 O1
Orbital characteristics A
EpochDecember 9, 2014
Aphelion3.446 AU
Perihelion1.559 AU
Semi-major axis3.467 AU
Orbital period6.40 yr
Jupiter MOID0.077 AU (11,500,000 km)[5]
Dimensions3.0 km[5]
Last perihelionMarch 18, 2022[1]
October 25, 2015[2]
May 25, 2009[3]
Next perihelion2028-Jun-28[4]

Comet Kopff or 22P/Kopff is a periodic comet in the Solar System. Discovered on August 23, 1906, it was named after August Kopff who discovered the comet. The comet was missed on its November 1912 return, but was recovered on its June 1919 return and has been seen at every apparition since.[3] Close approaches to Jupiter in 1938[5] and 1943 decreased the perihelion distance and orbital period.[6][7] 22P/Kopff’s last perihelion passage was 18 March 2022.[1] On 13 July 2028 it will pass 0.353 AU (52.8 million km) from Earth.[5]


Perihelion distance
at different epochs
Epoch Perihelion
1906 1.70
1945 1.50
1958 1.52
1990 1.58
2028 1.32[4]
2039 1.19

22P/Kopff was discovered at Königstuhl Observatory on Heidelberg, Germany.[7] Kopff analyzed photographic plates which he exposed on August 20, 1903, against pre-discovery images of the same region. On August 23, 1903, Kopff concluded it to be a comet with an estimated apparent magnitude of 11. On mid-September 1906, the short-period nature of the comet was recognized by a team headed by Kiel Ebell of the Berkeley Astronomical Department. The comet was missed when it made a return on November 25, 1912, however on June 25, 1919, astronomers recovered the comet. The comet was located less than three days from the predicted position. Over the next several returns to Earth, none were notable until the 1945 comet’s return when the comet peaked at magnitude 8.5. The increase in brightness was a result of Jupiter altering the comet’s orbit between the years of 1939 to 1945. This change in orbit brought the comet closer to the Sun. The 1951 return was unique due to the comet being 3 magnitudes fainter than what was expected when recovered in April 1951. But the comet still reached magnitude 10.5 in October 1951. A very close pass to Jupiter in 1954 increased the comet’s perihelion distance to 1.52 AU and increased the orbital period to 6.31 years.[7] On November 30, 1994, Carl W. Hergenrother was able to recover the comet at a stellar magnitude of 22.8 using the 1.5-m reflector at the Catalina Sky Survey.[7] The comet reached magnitude 7 during the 1996 perihelion passage.[8]

The comet nucleus is estimated to be 3.0 kilometers in diameter with an albedo of 0.05.[5] The nucleus is dark because hydrocarbons on the surface have been converted to a dark, tarry like substance by solar ultraviolet radiation.


  1. ^ a b MPC
  2. ^ Syuichi Nakano (2009-02-16). "22P/Kopff (NK 1749)". OAA Computing and Minor Planet Sections. Retrieved 2010-03-04.
  3. ^ a b "22P/Kopff (Returns and Appearances)". Seiichi Yoshida Comet Catalog. Retrieved 2010-02-24.
  4. ^ a b "Horizons Batch for 22P/Kopff (90000339) on 2028-Jun-28" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 2022-06-16. (JPL#K222/6 Soln.date: 2022-Jun-08)
  5. ^ a b c d e "JPL Small-Body Database Browser: 22P/Kopff" (last observation: 2014-03-29). Jet Propulsion Laboratory. Retrieved 2014-10-27.
  6. ^ "22P at Kazuo Kinoshita's Comets". 2014-02-13.
  7. ^ a b c d Kronk, Gary W. "22P/Kopff". Cometography. Retrieved 2010-02-25.
  8. ^ "22P/Kopff (1996)". Seiichi Yoshida. Retrieved 2010-02-25.