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42355 Typhon (/ˈtfɒn/; from Greek: Τυφών) is a scattered disc object that was discovered on February 5, 2002, by the NEAT program. It measures 162±7 km in diameter, and is named after Typhon, a monster in Greek mythology.

42355 Typhon
Typhon-echidna hst.jpg
Hubble Space Telescope image of Typhon and its moon Echidna, taken in 2006
Discovered byNEAT
Discovery date5 February 2002
MPC designation(42355) Typhon
Named after
2002 CR46
Scattered disc[1][2]


7:10 resonance
AdjectivesTyphonean, Typhonian
Orbital characteristics[1]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 2
Observation arc9563 days (26.18 yr)
Aphelion58.982252 AU (8.8236193 Tm)
Perihelion17.545721 AU (2.6248025 Tm)
38.263987 AU (5.7242110 Tm)
236.70 yr (86453.7 d)
0° 0m 14.991s / day
Earth MOID16.557 AU (2.4769 Tm)
Jupiter MOID12.1588 AU (1.81893 Tm)
Physical characteristics
Dimensions138±9 km[4]
162±7 km[5]
Mass≈9.082×1017 kg (calculated using a diameter of 138 km[4])
Mean density
9.67 h (0.403 d)[4]
B−V=0.74±0.02 V−R=0.52±0.01

A large moon was identified in 2006. It is named Echidna—formal designation (42355) Typhon I Echidna, /ɪˈkɪdnə/, from Greek: Έχιδνα—after Echidna, the monstrous mate of Typhon. It orbits Typhon at ~1300 km, completing one orbit in about 11 days. Its diameter is estimated to be 89±6 km. Typhon is the first known binary centaur,[6] using an extended definition of a centaur as an object on a non-resonant (unstable) orbit with the perihelion inside the orbit of Neptune.[7]


  1. ^ a b "JPL Small-Body Database Browser: (42355 Typhon)" (2008-03-14 last obs). Retrieved 12 April 2016.
  2. ^ "List Of Centaurs and Scattered-Disk Objects". Minor Planet Center. Retrieved 2008-09-21.
  3. ^ (42355) Typhon and Echidna
  4. ^ a b c d Duffard, R.; Pinilla-Alonso, N.; Santos-Sanz, P.; Vilenius, E.; Ortiz, J. L.; Mueller, T.; et al. (April 2014). ""TNOs are Cool": A survey of the trans-Neptunian region. XI. A Herschel-PACS view of 16 Centaurs" (PDF). Astronomy and Astrophysics. 564: 17. arXiv:1309.0946. Bibcode:2014A&A...564A..92D. doi:10.1051/0004-6361/201322377. Retrieved 3 June 2019.
  5. ^ a b Santos-Sanz, P., Lellouch, E., Fornasier, S., Kiss, C., Pal, A., Müller, T. G., Vilenius, E., Stansberry, J., Mommert, M., Delsanti, A., Mueller, M., Peixinho, N., Henry, F., Ortiz, J. L., Thirouin, A., Protopapa, S., Duffard, R., Szalai, N., Lim, T., Ejeta, C., Hartogh, P., Harris, A. W., & Rengel, M. (2012). “TNOs are Cool”: A Survey of the Transneptunian Region IV - Size/albedo characterization of 15 scattered disk and detached objects observed with Herschel Space Observatory-PACS
  6. ^ K. Noll; H. Levison; W. Grundy; D. Stephens (October 2006). "Discovery of a binary Centaur". Icarus. 184 (2): 611. arXiv:astro-ph/0605606. Bibcode:2006Icar..184..611N. doi:10.1016/j.icarus.2006.05.010.
  7. ^ J. L. Elliot; S. D. Kern; K. B. Clancy; A. A. S. Gulbis; R. L. Millis; M. W. Buie; et al. (February 2005). "The Deep Ecliptic Survey: A Search for Kuiper Belt Objects and Centaurs. II. Dynamical Classification, the Kuiper Belt Plane, and the Core Population" (PDF). The Astronomical Journal. 129 (2): 1117. Bibcode:2005AJ....129.1117E. doi:10.1086/427395.

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