(87) Sylvia, Romulus, and Remus

compiled by Wm. Robert Johnston
last updated 1 September 2005

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: 3.4902552804356 AU
orbital period P: 6.5207 y (=2381.7 d)
eccentricity e: 0.0796620231198216
perihelion distance q: 3.21221448359146 AU
aphelion distance Q: 3.76829608 AU
inclination i: 10.8560643032686°
argument of perihelion omega: 266.047724837443°
ascending node OMEGA: 73.330182435556°
mean anomaly M: 53.35606655137°
perihelion passage TP: 2004-08-30.0074652
Epoch: 18 AUG 2005
data arc: 1894-2005 (920 obs.)

orbital data, Romulus:
semimajor axis a: 1356 ± 5 km [M05a]
semimajor axis/primary radius a/Rp: 9.5 [M05a]
orbital period P: 3.6496 ± 0.0007 d [M05a]
eccentricity e: 0.001 ± 0.001 [M05a]
inclination i: 1.7° ± 1.0° [M05a]

orbital data, Remus:
semimajor axis a: 706 ± 5 km [M05a]
semimajor axis/primary radius a/Rp: 4.9 [M05a]
orbital period P: 1.3788 ± 0.0007 d [M05a]
eccentricity e: 0.016 ± 0.011 [M05a]
inclination i: 2.0° ± 1.0° [M05a]

other data, primary:
mean diameter: 286 km [M05a]
triaxial dimensions: 384 x 264 x 232 km [M05a]
triaxial ratios a/b, b/c: 1.46, 1.14 [M05a]
absolute magnitude H: 6.94 [JPL]
rotation period: 0.2159853 d (=5.18365 h) [SBb]
amplitude delta M: 0.30-0.62 [MPb]
color index U-B: 0.251 ± 0.026 [SBa]
color index B-V: 0.71 [JPL]
color index V-R: ?
color index R-I: ?
slope parameter G: (0.15) [a]
geometric albedo: 0.0435 ± 0.005 [IR]
mass: (1.478±0.006)x1019 kg [M05a]
density: 1.2 ± 0.1 g/cm3 [M05a]
type: P [SBd]; X [JPL]

other data, Romulus:
diameter: 18 ± 4 km [M05a]
diameter ratio Ds/Dp: (0.06)
component magnitude difference: 6.24 ± 0.2 [I7590]
3.8 [M05a]
rotation period: ?

other data, Remus:
diameter: 7 ± 2 km [M05a]
diameter ratio Ds/Dp: (0.02)
component magnitude difference: 4.2 [M05a]
rotation period: ?

--(87) Sylvia--discovery and notes:

Primary discovered 16 May 1866 from Madras, India, by N. R. Pogson. Alternate designation A909 GA.

Companion S/2001 (87) 1 discovered 18 February 2001 by M. E. Brown and J. L. Margot from the Keck II telescope at Mauna Kea; announced 23 February 2001. Permanently designated (87) Sylvia I Romulus in 2005.

Companion S/2004 (87) 1 discovered 9 August 2004 by Franck Marchis, Pascal Descamps, Daniel Hestroffer, and Jerome Berthier from the VLT adaptive optics telescope at European Southern Observatory, Cerro Paranel, Chile; announced 10 August 2005. Permanently designated (87) Sylvia II Remus in 2005.

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

--Links, more technical:

--Links, less technical:

--Links to ADS abstracts:


© 2001-2004, 2005 by Wm. Robert Johnston.
Last modified 1 September 2005.
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