Actaea (moon)

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Actaea
Discovery
Discovered by Keith S. Noll, Harold F. Levison, Denise C. Stephen, William M. Grundy
Discovery date 21 Jul 2006
Designations
S/2006 (120347) 1,
Salacia I
Adjectives Actaean
Orbital characteristics
5619 ± 87 km
Eccentricity 0,0084 ± 0,0076
5,49380 ± 0,00016 days
Satellite of Salacia
Physical characteristics
Dimensions 303 ± 35 km
Mass 1,86 × 1019 kg
Mean density
1,16 +0,59/-0,36 g/cm³
≈ 0.05 km/s
Albedo ≈ 0,035 +0,010/−0,007
1,9 mag

Actaea, officially (120347) Salacia I Actaea, is the single known natural satellite of the cubewano 120347 Salacia. Its diameter is estimated 300 km, which is ⅓ of the diameter of Salacia; thus, Salacia and Actaea are viewed by some to be a binary object. Actaea is about the sixth-biggest known moon of a Kuiper belt object, after Charon (1212 km), Dysnomia (685 km), Vanth (378 km), Ilmarë (361 km) and Hiiaka (320 km).

Discovery and name

It was discovered on 21 July 2006 by Keith S. Noll, Harold Levison, Denise Stephens and Will Grundy with the Hubble Space Telescope.[1] On 18 February 2011, it was officially named Actaea after the nereid Aktaia.

Orbit

Actaea orbits its primary every 5.49380±0.00016 d at a distance of 5619±87 km and with an eccentricity of 0.0084±0.0076.[2] The ratio of its semi-major axis to its primary's Hill radius is 0.0023, the tightest trans-Neptunian binary with a known orbit.[3]

Physical characteristics

Actaea is 2.372±0.060 magnitudes fainter than Salacia,[4] implying a diameter ratio of 2.98 for equal albedos.[3] Hence, assuming equal albedos, it has a diameter of 303±35 km[4] Actaea has the same color as Salacia (V−I = 0.89±0.02 and 0.87±0.01, respectively), supporting the assumption of equal albedos.[3] It has been calculated that the Salacia system should have undergone enough tidal evolution to circularize their orbits, which is consistent with the low measured eccentricity, but that the primary need not have been tidally locked.[3] The low density calculated for the system (1,16 g/cm3)implies that both Salacia and Actaea consist chiefly of water ice. Salacia and Actaea will next occult each other in 2067.[3] The mass of the system is 4,66 ± 0,22  × 1020 kg, with about 4% of this being in Actaea.[3]

References

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  2. Johnston Archive: (120347) Salacia and Actaea
  3. 3.0 3.1 3.2 3.3 3.4 3.5 Lua error in package.lua at line 80: module 'strict' not found.
  4. 4.0 4.1 Lua error in package.lua at line 80: module 'strict' not found.