Asteroids with Satellites Database--Johnston's Archive

(6690) Messick

compiled by Wm. Robert Johnston
last updated 7 October 2025

--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: 2.25987294857 AU
orbital period P: 3.3973026475 yr
(= 1240.86479201 d)
eccentricity e: 0.15405443029
perihelion distance q: 1.911729509 AU
aphelion distance Q: 2.60801638818 AU
inclination i: 3.756432448°
argument of perihelion ω: 333.21183564°
ascending node Ω: 319.21382932°
mean anomaly M: 48.95091218°
perihelion passage TP: 2025 Jun 05.2737126
Epoch: 2025 Nov 21
data arc: 1981-2025 (4371 obs.)
Earth MOID: 0.89485 AU
Jupiter Tisserand invariant TJ: 3.602

orbital data, secondary:
semimajor axis as: 9.7 km [*E]
separation/primary radius as/rp:5.1 [*E]
separation/Hill radius as/rH:0.017 [*E]
orbital period Ps: 1.2396 ± 0.0008 d [B25m]
eccentricity es: ?
normalized ang. mom. αL: ?

other data, system (combined):
absolute mag. H: 13.68 [MPC]
slope parameter G: (0.15) [*A]
effective diameter dE: 3.98 ± 0.19 km [M19a]
geometric albedo: 0.486 ± 0.067 [M19a]
color index U-B: ?
color index B-V: ?
taxonomic type: ?
mass m: ?
density ρ: (1.6 g/cm3) [*A]
Hill radius rH: 570 km [*E]

other data, primary:
diameter dp: 3.77 ± 0.18 km [*D]
dimensions :~4.2 x ~3.4 km [*E]
axial ratios a/b, b/c:1.2, ? [*E]
rotation period RPp: 3.0248 ± 0.0001 h [B25m]
amplitude in mag., rotational ΔM: 0.24 [B25m]
amplitude in mag., mutual events ΔM:0.12 [B25m]
pole direction Β, λ: ? , ?

other data, secondary:
diameter ds: 1.28 ± 0.10 km [*D]
diameter ratio ds/dp: 0.34 ± 0.02 [B25m]
component mag. difference ΔM: 2.34 ± 0.13 [*D]
rotation period RPs: ?

-- (6690) Messick --discovery and notes:

Primary discovered 1981 Sep 25 from Anderson Mesa Station, Flagstaff, Arizona, USA by B. A. Skiff. Alternate designation(s): 1981 SY1, 1988 UM. Linked to prediscovery observations from 1981 Sep 02. Permanent number assigned 1995 Dec 07.

Named 1999 Sep 28 for Hank H. Messick (1955-) [MPC036126].

Companion discovered 2025 Aug 14 by V. Benishek, P. Pravec, A. Leroy, C. Biba, S. Sylla, N. Tovolahy, M. Avotra, F. Vachier, J. Oey, R. Durkee, D. Augustin, A. Klotz, J. Berthier, and P. Thierry using lightcurve observations from Sopot Observatory, Serbia; Ecole du Monde Besely, Madagascar; Observatoire des Makes, Reunion, France; Blue Mountains Observatory, Leura, New South Wales, Australia; Shed of Science South Observatory, Pontotoc, Texas, USA; e-EyE Observatory, Spain. Announced 2025 Oct 07 [B25m].

--Links, more technical:

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© 2025 by Wm. Robert Johnston.
Last modified 7 October 2025.
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