Asteroids with Satellites Database--Johnston's Archive

(65489) Ceto and Phorcys

compiled by Wm. Robert Johnston
last updated 11 May 2014
under construction--testing upgrades!

--Orbital and physical data--

(See this page for definitions of quantities; source codes in brackets, see this link for full references; *A, *D, and *E indicate assumed, derived, and estimated values, respectively.)

dynamical type, primary: Centaur


orbital data, primary (osculating elements) [JPL] :
semimajor axis a: 101.903 AU
orbital period P: 1028.702 yr (= 375733.2 d)
eccentricity e: 0.825449
perihelion distance q: 17.78733 AU
aphelion distance Q: 186.019 AU
inclination i: 22.278415°
argument of perihelion ω: 319.77845°
ascending node Ω: 171.90476°
mean anomaly M: 8.6746°
perihelion passage TP: 1989 Aug 08.27
Epoch: 2014 May 23
data arc: 1987-2012 (80 obs.)
Earth MOID: 16.833 AU
Jupiter Tisserand invariant TJ: 4.674
Neptune Tisserand invariant TN:2.22 [*D]


orbital data, secondary:
semimajor axis as: 1840 ± 44 km [G07b]
separation/primary radius as/rp:17 [*D]
separation/Hill radius as/rH:0.0071 [*D]
orbital period Ps: 9.554 ± 0.011 d [G07b]
eccentricity es: 0.004 ± 0.009 [G07b]
inclination is:68.8°± 2.9 [*G06a]
normalized ang. mom. αL: ?

other data, system (combined):
absolute mag. H: 6.4 [MPC]
6.54 ± 0.06 [S12a]
slope parameter G: 0.15 [*A]
effective diameter dE: 281 ± 11/11 km [S12a]
geometric albedo: 0.056 ± 0.006/0.006 [S12a]
color index U-B: 0.23 [J07a]
color index B-V: 0.86 [T03b]
color index V-R:0.56± 0.03 [T03b]
color index B-R:1.42± 0.04 [T03b]
taxonomic type: ?
mass m: 5.41x1018 ± 4.2x1017 kg [G07b]
density ρ: 0.64 ± 0.16/0.13 g/cm3 [S12a]
Hill radius rH: 260000 km [*D]

other data, primary:
diameter dp: 223 ± 10/10 km [S12a]
axial ratios a/b, b/c:1.13;? [D08b]
rotation period RPp: 4.43 ± 0.03 h [D08b]
amplitude in mag., rotational ΔM: 0.13 ± 0.02 [D08b]
pole direction : ? ; ?


other data, secondary:
diameter ds: 171 ± 10/10 km [S12a]
diameter ratio ds/dp: 0.764 ± 0.011 [G07b]
component mag. difference ΔM: 0.56 ± 0.03 [*G06a]
rotation period RPs: ?

-- (65489) Ceto and Phorcys --discovery and notes:

Primary discovered 2003 Mar 22 from Palomar Observatory, California, USA by C. A. Trujillo and M. E. Brown. Alternate designation(s): 2003 FX128 . Linked to prediscovery observations from 1987 Jan 31. Permanent number assigned 2003 Jun 14.

Named 2006 Nov 09 for the Greek mythological sea creature [MPC57952].

Companion discovered 2006 Apr 11 by K. S. Noll et al. using HST observations from Hubble Space Telescope. Announced 2006 Aug [I8778]. Permanent designation I Phorcys, assigned 2006 Nov 09; named for the Greek mythological sea creature [MPC57952].

--Links, more technical:

--Links, less technical:

--Links to ADS abstracts:


© 2006-2008, 2014 by Wm. Robert Johnston.
Last modified 11 May 2014.
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