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

compiled by Wm. Robert Johnston
last updated 25 November 2008

Orbital elements and other data (Assumed or derived values in parenthesis, my estimates in italics and parenthesis. Source identifications in brackets, see this link for sources):

orbital data, primary (osculating elements) [JPL]:
semimajor axis a: 3.44648624887381 AU
orbital period P: 6.3984 y (=2337.1 d)
eccentricity e: 0.142841034156579
perihelion distance q: 2.95418658887824 AU
aphelion distance Q: 3.93878591 AU
inclination i: 7.57876272845518°
argument of perihelion omega: 295.459147727556°
ascending node OMEGA: 73.385497306715°
mean anomaly M: 172.26636548324°
perihelion passage TP: 2002-07-26.6924882
Epoch: 18 AUG 2005
data arc: 1872-2005 (713 obs.)

orbital data, secondary:
semimajor axis a: 794.7 ± 2.1 km [M03d]
768 ± 11 km [MAf]
semimajor axis/primary radius a/Rp: (7.6)
orbital period P: 1.62722 ± 0.00007 d [I8285]
2.582 ± 0.002 d [MAf]
eccentricity e: 0.001 ± 0.001 [MAf]
inclination i: 3° ± 2° [MAf]

other data, primary:
diameter: 209.0 ± 4.7 km [IR];
230 km x 120 km x 120 km or
265 km x 180 km x 180 km [MAi]
triaxial ratios a/b, b/c: 1.10, 1.00 [SBb]
absolute magnitude H: 7.31 [JPL]
rotation period: 9.238 ± 0.010 h [B96b];
5.551 h [MAi]
amplitude delta M: 0.03-0.25 [MPb]
color index U-B: 0.425 ± 0.087 [SBa]
color index B-V: 0.73 ± 0.01 [B96b]
color index V-R: ?
color index R-I: ?
slope parameter G: (0.15) assumed
geometric albedo: 0.048 ± 0.002 [IR]
mass: 1.47x1019 kg [M03d]
(9.3 ± 1.6)x1018 [V00a]
5.4x1018 kg [MAf]
density: 3.1 ± 0.8 g/cm3 [M03d]
1.8 ± 0.4 g/cm3 [V00a]
1.1 ± 0.3 g/cm3 [MAf]
type: C [SBd]

other data, secondary:
diameter: 18 km [I8285]
diameter ratio Ds/Dp: (0.09)
component magnitude difference: 6.1 [M03d]
rotation period: ?

--(121) Hermione--discovery and notes:

Primary discovered 12 May 1872 by James C. Watson from Ann Arbor, Michigan, USA.

Companion discovered 28 September 2002 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 the Keck II telescope at Mauna Kea; announced 30 September 2002. The name "LaFayette" has been proposed [MAf].

See more information and links at Asteroid/Comet Connection Catchall Catalog page

--Links, more technical:

--Links, less technical:

--Links to ADS abstracts:


© 2002-2005, 2008 by Wm. Robert Johnston.
Last modified 25 November 2008.
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