Asteroids with Satellites Database--Johnston's Archive

(5261) Eureka

compiled by Wm. Robert Johnston
last updated 16 November 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: Mars trojan asteroid, L5


orbital data, primary (osculating elements) [JPL] :
semimajor axis a: 1.52353322 AU
orbital period P: 1.880519722 yr
(= 686.8728008 d)
eccentricity e: 0.064859679
perihelion distance q: 1.424717344 AU
aphelion distance Q: 1.6223490956 AU
inclination i: 20.2803507°
argument of perihelion ω: 95.470352°
ascending node Ω: 245.062272°
mean anomaly M: 295.624269°
perihelion passage TP: 2015 Apr 10.82761
Epoch: 2014 Dec 09
data arc: 1979-2014 (757 obs.)
Earth MOID: 0.499711 AU
Jupiter Tisserand invariant TJ: 4.428


orbital data, secondary:
semimajor axis as: 2.1 km [*E]
separation/primary radius as/rp:3.5 [*E]
separation/Hill radius as/rH:0.016 [*E]
orbital period Ps: 0.7054 ± 0.0004 d [K14a]
eccentricity es: ?
normalized ang. mom. αL: ?

other data, system (combined):
absolute mag. H: 16.1 [MPC]
slope parameter G: (0.15) [*A]
effective diameter dE: 1.28 ± 0.07 km [T07a]
geometric albedo: 0.39 ± 0.155 [T07a]
color index U-B: ?
color index B-V: ?
taxonomic type: Sr (SMASSII) [JPL]
mass m: ?
density ρ: (1.6 g/cm3) [*A]
Hill radius rH: 130 km [*E]

other data, primary:
diameter dp: 1.19 km [*D]
rotation period RPp: 2.6902 ± 0.0003 h [K14a]
amplitude in mag., rotational ΔM: 0.064 [K14a]
amplitude in mag., mutual events ΔM:0.175 ±0.025 [K14a]
pole direction Β, λ: ? , ?


other data, secondary:
diameter ds: 0.46 km [*D]
diameter ratio ds/dp: >0.39 ± 0.02 [K14a]
component mag. difference ΔM: 2.0 [*D]
rotation period RPs: ?

-- (5261) Eureka --discovery and notes:

Primary discovered 1990 Jun 20 from Palomar Observatory, California, USA by Holt and Levy. Alternate designation(s): 1990 MB . Linked to prediscovery observations from 1979 Nov 21. Permanent number assigned 1992.

Companion discovered 2011 Nov 28 using lightcurve observations. Announced 2014 Sep [K14a].

--Links, more technical:

--Links, less technical:

--Links to ADS abstracts:


© 2014 by Wm. Robert Johnston.
Last modified 16 November 2014.
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