Asteroids with Satellites Database--Johnston's Archive

(1656) Suomi

compiled by Wm. Robert Johnston
last updated 27 May 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: Mars crossing asteroid


orbital data, primary (osculating elements) [JPL] :
semimajor axis a: 1.8778819257 AU
orbital period P: 2.5733711212 yr
(= 939.915539 d)
eccentricity e: 0.123171623
perihelion distance q: 1.646580161 AU
aphelion distance Q: 2.1091836901 AU
inclination i: 25.0658521°
argument of perihelion ω: 287.499175°
ascending node Ω: 175.5387855°
mean anomaly M: 197.748597°
perihelion passage TP: 2021 Jul 28.630099
Epoch: 2020 May 31
data arc: 1942-2020 (2393 obs.)
Earth MOID: 0.754228 AU
Jupiter Tisserand invariant TJ: 3.851


orbital data, secondary:
semimajor axis as: 30 km [*E]
separation/primary radius as/rp:7.9 [*E]
separation/Hill radius as/rH:0.031 [*E]
orbital period Ps: 2.413 ± 0.001 d [W20c]
eccentricity es: ?
normalized ang. mom. αL: ?

other data, system (combined):
absolute mag. H: 12.8 [MPC]
slope parameter G: (0.15) [*A]
effective diameter dE: 7.86 ± 0.7 km [JPL]
geometric albedo: 0.156 ± 0.032 [JPL]
color index U-B: ?
color index B-V: ?
taxonomic type: S (Tholen) [JPL]
mass m: ?
density ρ: (1.6 g/cm3) [*A]
Hill radius rH: 980 km [*E]

other data, primary:
diameter dp: 7.61 km [*D]
rotation period RPp: 2.5885 ± 0.0001 h [W20c]
amplitude in mag., rotational ΔM: 0.11 ± 0.01 [W20c]
amplitude in mag., mutual events ΔM:0.07 ±0.01 [W20c]
pole direction Β, λ: ? , ?


other data, secondary:
diameter ds: >1.98 km [*D]
diameter ratio ds/dp: >0.26 ± 0.02 [W20c]
component mag. difference ΔM: <2.9 [*D]
rotation period RPs: ?

-- (1656) Suomi --discovery and notes:

Primary discovered 1942 Mar 11 from Turku, Finland by Y. Vaisala. Alternate designation(s): 1942 EC, 1955 HL. Linked to prediscovery observations from 1942 Mar 10. Permanent number assigned -.

Named 1976 Feb 20 [MPC003932].

Companion discovered 2020 Jun 09 by B. D. Warner, R. D. Stephens, and A. W. Harris using lightcurve observations from Center for Solar System Studies, Landers, California, USA. Announced 2020 Sep [W20c].

--Links, more technical:

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--Links to ADS abstracts:


© 2020 by Wm. Robert Johnston.
Last modified 11 October 2020
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