Asteroids with Satellites Database--Johnston's Archive

(121) Hermione and S/2002 (121) 1 ("LaFayette")

compiled by Wm. Robert Johnston
last updated 21 September 2014

--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: main belt asteroid, outer

orbital data, primary (osculating elements) [JPL] :
semimajor axis a: 3.450115270 AU
orbital period P: 6.408532783 yr
(= 2340.716599 d)
eccentricity e: 0.134268194
perihelion distance q: 2.98687453 AU
aphelion distance Q: 3.913356016 AU
inclination i: 7.5964736°
argument of perihelion ω: 298.357981°
ascending node Ω: 73.145747°
mean anomaly M: 301.356905°
perihelion passage TP: 2015 Jun 08.29685
Epoch: 2014 May 23
data arc: 1872-2013 (1624 obs.)
Earth MOID: 1.9961 AU
Jupiter Tisserand invariant TJ: 3.108

orbital data, secondary:
binary dynamical type:L [P07f]
semimajor axis as: 747 ± 11 km [D09a]
separation/primary radius as/rp:8.0 [*D]
separation/Hill radius as/rH:0.018 [*D]
orbital period Ps: 2.563 ± 0.0021 d [D09a]
eccentricity es: 0.00 [D09a]
inclination is:3° ± 2° [M05f]
normalized ang. mom. αL: 0.73 [P07f]

other data, system (combined):
absolute mag. H: 7.31 [MPC]
slope parameter G: (0.15) [*A]
effective diameter dE: 190 km [*D]
geometric albedo: 0.05 ± 0.01 [D09a]
color index U-B: 0.425 [T95a]
color index B-V: 0.73 [B96c]
taxonomic type: Ch (SMASSII) [JPL]
C (Tholen) [JPL]
mass m: 4.7x1018 ± 2x1017 kg [D09a]
density ρ: 1.4 ± 0.35 g/cm3[D09a]
Hill radius rH: 41000 km [*D]

other data, primary:
diameter dp: 187 ± 6 km [D09a]
rotation period RPp: 5.551 ± 0.000 h [D09a]
amplitude in mag., rotational ΔM: 0.7 [W14e]
pole direction Β, λ: ? , ?

other data, secondary:
diameter ds: 32 km [D09a]
diameter ratio ds/dp: 0.171 [*D]
component mag. difference ΔM: 3.8 [*D]
rotation period RPs: ?

-- (121) Hermione and S/2002 (121) 1 --discovery and notes:

Primary discovered 1872 May 12 from Ann Arbor, Michigan, USA by J. C. Watson. Alternate designation(s): 1970 VE. Permanent number assigned 1872.

Named - for the Greek mythological daughter of Menelaus.

Companion discovered 2002 Sep 28 by W. J. Merline, P. M. Tamblyn, C. Dumas, L. M. Close, C. R. Chapman, F. Menard, W. M. Owen, D. C. Slater, and J. Pepin using adaptive optics telescope observations from W. M. Keck II Telescope, Mauna Kea, Hawaii, USA. Announced 2002 Sep 30 [M02e]. Provisional designation S/2002 (121) 1. Proposed name: "LaFayette".

--Links, more technical:

--Links, less technical:

--Links to ADS abstracts:

© 2002-2008, 2014 by Wm. Robert Johnston.
Last modified 21 September 2014.
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