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C/2017 K2 (PANSTARRS) is a non-periodic comet with a hyperbolic orbit, discovered in May 2017 at a distance beyond the orbit of Saturn when it was 16.09 AU (2.4 billion km) from the Sun. Precovery images from 2013 were located by July.[7] It has been in the constellation of Draco since July 2007. As of April 2018, the 3-sigma uncertainty in the current distance of the comet from the Sun is ±30000 km.

Distant active comet C 2017 K2.jpg
June 2017 by Hubble's Wide Field Camera 3[1]
Discovery date 21 May 2017[2]
Orbital characteristics [ A]
Epoch 2022-12-07 (2459920.5)
Observation arc 4.55 years
Aphelion ~45000 AU[a]
Perihelion 1.7969 AU[3]
Eccentricity 1.0008
Orbital period millions of years inbound[a]
~26000 years (outbound)
Inclination 87.563°
Earth MOID 1.10 AU (165 million km)
Jupiter MOID 1.29 AU
Dimensions Rn between 14 km (8.7 mi) and 80 km (50 mi)[5]
maximum Dn ~18 km (11 mi)[6]
Next perihelion 2022-Dec-19[3][4][b]

Research with the Canada–France–Hawaii Telescope (CFHT) infers the comet nucleus to have a radius between 14 and 80 km, so there is a chance the nucleus could be as large as C/1995 O1 (Hale-Bopp)".[5] But research with the Hubble Space Telescope (HST) estimates the nucleus to have a circular equivalent diameter of less than 18 km.[6]

Around 2022-Jul-06 the comet will cross the celestial equator and then around 2022-Jul-14 it will pass 1.8 AU (270 million km) from Earth.[8] It will reach perihelion around 2022-Dec-19, close to the orbit of Mars.[3][4][b]

C2017 K2 skypath.png
Path of C/2017 K2 in the sky


  1. ^ "Distant active comet C/2017 K2". Retrieved 3 October 2017. 
  2. ^ "MPEC 2017-K35 : COMET C/2017 K2 (PANSTARRS)". IAU Minor Planet Center. 2017-05-24. Retrieved 2017-10-21.  (CK17K020) (3 day obs arc)
  3. ^ a b c "C/2017 K2 (PANSTARRS) Orbit". Minor Planet Center. Archived from the original on 2017-11-13. Retrieved 2017-11-13. 
  4. ^ a b Seiichi Yoshida. "C/2017 K2 ( PanSTARRS )". Seiichi Yoshida's Comet Catalog. Retrieved 2017-11-15. 
  5. ^ a b Meech, Karen (2017). "CO-Driven Activity in Comet C/2017 K2 (PANSTARRS)". The Astrophysical Journal Letters. 849 (1). arXiv:1710.03876 . Bibcode:2017ApJ...849L...8M. doi:10.3847/2041-8213/aa921f. 
  6. ^ a b Jewitt, David (2017). "A Comet Active Beyond the Crystallization Zone". The Astrophysical Journal. 847 (2). arXiv:1709.10079 . Bibcode:2017ApJ...847L..19J. doi:10.3847/2041-8213/aa88b4. 
  7. ^ "MPEC 2017-N26 : COMET C/2017 K2 (PANSTARRS)". IAU Minor Planet Center. 2017-07-01. Retrieved 2017-10-21. 
  8. ^ Hubble Spots Farthest-Ever Incoming Active Comet September 29, 2017


  1. ^ a b Computed with JPL Horizons using a barycentric solution. Ephemeris Type: Orbital Elements / Center: @0 (To be outside planetary region, inbound epoch 1950 and outbound epoch 2050)
  2. ^ a b Perihelion passage: Given perihelion is still 5 years away, an epoch of 2022 gives a more accurate perihelion date that properly accounts for planetary perturbations. An epoch 2017 unperturbed two-body solution (Sun+comet) gives a date of 2022-Dec-21. Integrating the orbit with JPL Horizons which accounts for planetary perturbations gives a date of 2022-Dec-19. The Minor Planet Center's Epoch Dec 2022 solution also gives a date of 2022 Dec. 19

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