Asteroids with Satellites Database--Johnston's Archive

(5500) Twilley

compiled by Wm. Robert Johnston
last updated 21 December 2019

--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


orbital data, primary (osculating elements) [JPL] :
semimajor axis a: 2.2796606587 AU
orbital period P: 3.4419559399 yr
(= 1257.1981508 d)
eccentricity e: 0.089623438
perihelion distance q: 2.075349633 AU
aphelion distance Q: 2.4839716843 AU
inclination i: 4.3972559°
argument of perihelion ω: 341.244747°
ascending node Ω: 112.51406°
mean anomaly M: 279.425161°
perihelion passage TP: 2020 Feb 02.384828
Epoch: 2019 Apr 27
data arc: 1955-2019 (1940 obs.)
Earth MOID: 1.09272 AU
Jupiter Tisserand invariant TJ: 3.597


orbital data, secondary:
semimajor axis as: 7.8 km [*E]
separation/primary radius as/rp:3.6 [*E]
separation/Hill radius as/rH:0.011 [*E]
orbital period Ps: 0.7315 ± 0.0003 d [C19a]
eccentricity es: ?
normalized ang. mom. αL: ?

other data, system (combined):
absolute mag. H: 13.6 [MPC]
slope parameter G: (0.15) [*A]
effective diameter dE: 4.48 ± 0.12 km [M**]
geometric albedo: 0.35 ± 0.056 [M**]
color index U-B: ?
color index B-V: ?
taxonomic type: ?
mass m: ?
density ρ: (1.6 g/cm3) [*A]
Hill radius rH: 700 km [*E]

other data, primary:
diameter dp: 4.33 km [*D]
rotation period RPp: 2.9554 ± 0.0002 h [C19a]
amplitude in mag., rotational ΔM: 0.15 [C19a]
amplitude in mag., mutual events ΔM:0.105 ±0.025 [C19a]
pole direction Β, λ: ? , ?


other data, secondary:
diameter ds: >1.17 km [*D]
diameter ratio ds/dp: >0.27 [C19a]
component mag. difference ΔM: <2.8 [*D]
rotation period RPs: ?

-- (5500) Twilley --discovery and notes:

Primary discovered 1981 Nov 24 from Anderson Mesa, Flagstaff, Arizona, USA by E. Bowell. Alternate designation(s): 1981 WR, 1974 VU2, 1988 XV. Linked to prediscovery observations from 1955 Mar 23. Permanent number assigned 1993 Apr 06.

Named 1995 Nov 07 for Royston C. Twilley (1914-) [MPC025976].

Companion discovered 2017 Feb by M. Conjat, R. Montaigut, D. Augustin, C. Pinturaud, R. Behrend, P. Griveaud, D. mata, and J.-P. Rivet using lightcurve observations from Nice Observatory, France; Club d’Astronomie de Lyon Ampere, France; Pichasca, Chile; Haute-Provence Observatory; Geneva Observatory, Switzerland; Calern Observatory, France. Announced 2019 Dec 20 [C19a].

--Links, more technical:

--Links, less technical:

--Links to ADS abstracts:


© 2019 by Wm. Robert Johnston.
Last modified 21 December 2019.
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