Actaea (moon)

Last updated

Actaea
Salacia Hubble.png
Salacia and its moon Actaea, imaged by the Hubble Space Telescope on 21 July 2006
Discovery
Discovered by Keith S. Noll, Harold F. Levison, Denise C. Stephen, William M. Grundy
Discovery date21 July 2006
Designations
Designation
Salacia I
Pronunciation /ækˈtə/
S/2006 (120347) 1
Adjectives Actaean /ækˈtən/
Orbital characteristics [1]
5724±27 km
Eccentricity 0.0098±0.0038
5.493882±0.000023 days
Inclination 23.59±0.36°
45.2±1.6°
134±23°
Satellite of Salacia
Physical characteristics
Dimensions284±10 km [1]
Albedo ≈0.035 +0.010/−0.007[ citation needed ]
Spectral type
V–I = 0.89±0.02 (Actaea)
1.9 mag[ citation needed ]

    Actaea, officially (120347)Salacia I Actaea, is a natural satellite of the classical Kuiper belt planetoid 120347 Salacia. Its diameter is estimated 300 km (190 mi), which is approximately one-third the diameter of Salacia; thus, Salacia and Actaea are viewed by some astronomers to be a binary system.[ by whom? ] Assuming that the following size estimates are correct, Actaea is about the sixth-biggest known moon of a trans-Neptunian object, after Charon (1212 km), Dysnomia (700 km), [2] Vanth (443 km), [3] Ilmarë (326 km) [4] and Hiʻiaka (320 km), but possibly also Hiisi (250 km).

    Contents

    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. [5] On 18 February 2011, it was officially named Actaea after the nereid Aktaia.

    Orbit

    Simulation of Actaea's orbit relative to Salacia Salacia Actaea orbit simulation.png
    Simulation of Actaea's orbit relative to Salacia

    Actaea orbits its primary every 5.493 d at a distance of 5619±87 km and with an eccentricity of 0.0084±0.0076. [6] 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. [7]

    Physical characteristics

    Actaea is 2.372±0.060 magnitudes fainter than Salacia, [8] implying a diameter ratio of 2.98 for equal albedos. [7] Hence, assuming equal albedos, it has a diameter of 303±35 km [8] 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. [7] 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. [7] 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. [7] The mass of the system is 4.66 ± 0.22  × 1020 kg, with about 4% of this being in Actaea. [7]

    Related Research Articles

    90482 Orcus Trans-Neptunian object and dwarf planet

    90482 Orcus, provisional designation 2004 DW, is a trans-Neptunian dwarf planet with a large moon, Vanth. It has a diameter of 910 km (570 mi). The surface of Orcus is relatively bright with albedo reaching 23 percent, neutral in color and rich in water ice. The ice is predominantly in crystalline form, which may be related to past cryovolcanic activity. Other compounds like methane or ammonia may also be present on its surface. Orcus was discovered by American astronomers Michael Brown, Chad Trujillo, and David Rabinowitz on 17 February 2004.

    <span class="nowrap">(55565) 2002 AW<sub>197</sub></span>

    (55565) 2002 AW197 is a classical, non-resonant trans-Neptunian object from the Kuiper belt in the outermost region of the Solar System, also known as cubewano. With a likely diameter of at least 700 kilometers (430 miles), Brown considers it a highly likely dwarf planet candidate. Tancredi notes that photometric observations suggest that it is a spheroid with a high albedo and small albedo spots. However, its low albedo suggests it does not have planetary geology. It is approximately tied with 2002 MS4 and 2013 FY27 (to within measurement uncertainties) as the largest unnamed object in the Solar System. It was discovered at Palomar Observatory in 2002 and has a rotation period of 8.8 hours and a moderately red color.

    <span class="nowrap">(55637) 2002 UX<sub>25</sub></span> Spitzer dwarf-planet candidate

    (55637) 2002 UX25 is a trans-Neptunian object that orbits the Sun in the Kuiper belt beyond Neptune. This TNO briefly garnered scientific attention when it was found to have an unexpectedly low density of about 0.82 g/cm3.

    Namaka (moon) Smaller moon of Haumea

    Namaka is the smaller, inner moon of the trans-Neptunian dwarf planet Haumea. It is named after Nāmaka, the goddess of the sea in Hawaiian mythology and one of the daughters of Haumea.

    58534 Logos

    58534 Logos, or as a binary system (58534) Logos-Zoe, is a trans-Neptunian object and binary system from the classical Kuiper belt, approximately 77 kilometers (48 miles) in diameter. The bright cubewano belonged to the cold population and has a 66-kilometer sized companion named Zoe. The system mass is (4.58±0.07)×1017 kg.

    79360 Sila–Nunam

    79360 Sila–Nunam, provisional designation 1997 CS29, is a double cold classical Kuiper belt object (cubewano) with components of almost equal size, orbiting beyond Neptune in the Solar System. The name of the system is the combined names of the two bodies, Sila and Nunam.

    174567 Varda Trans-Neptunian object

    174567 Varda (provisional designation 2003 MW12) is a binary trans-Neptunian planetoid of the resonant hot classical population of the Kuiper belt, located in the outermost region of the Solar System. Its moon, Ilmarë, was discovered in 2009.

    <span class="nowrap">(84922) 2003 VS<sub>2</sub></span> Trans-Neptunian object

    (84922) 2003 VS2 is a trans-Neptunian object discovered by the Near Earth Asteroid Tracking program on 14 November 2003. Like Pluto, it is in a 2:3 orbital resonance with Neptune and is thus a plutino. Analysis of light-curve suggests that it is not a dwarf planet.

    120347 Salacia Possible dwarf planet

    120347 Salacia, provisional designation 2004 SB60, is a large planetoid in the Kuiper belt, approximately 850 kilometers in diameter. As of 2018, it is located 44.8 astronomical units from the Sun, and reaches apparent magnitude 20.7 at opposition.

    42355 Typhon

    42355 Typhon (; prov. designation: 2002 CR46), is a scattered disc object that was discovered on February 5, 2002, by the NEAT program. It measures 162±7 km in diameter, and is named after Typhon, a monster in Greek mythology.

    88611 Teharonhiawako

    88611 Teharonhiawako, or (88611) Teharonhiawako-Sawiskera as a binary, is a trans-Neptunian object and a member of the cold classical Kuiper belt, measuring about 220 km in diameter. It is a binary object, with a large companion named Sawiskera, which at 126 km in diameter is about two-thirds the size of its primary.

    65489 Ceto

    65489 Ceto, as a binary also (65489) Ceto/Phorcys, is a binary trans-Neptunian object (TNO) discovered on March 22, 2003 by Chad A. Trujillo and Michael Brown at Palomar. It is named after the sea goddess Ceto from Greek mythology. It came to perihelion in 1989.

    229762 Gǃkúnǁʼhòmdímà Trans-Neptunian object

    229762 Gǃkúnǁʼhòmdímà, provisional designation 2007 UK126, is a trans-Neptunian object and binary system from the extended scattered disc, located in the outermost region of the Solar System. It was discovered on 19 October 2007 by American astronomers Megan Schwamb, Michael Brown, and David Rabinowitz at the Palomar Observatory in California and measures approximately 600 kilometers (400 miles) in diameter. This medium-sized TNO appears to be representative of a class of mid-sized objects under approximately 1000 km that have not collapsed into fully solid bodies. Its 100-kilometer moon was discovered by Keith Noll, Will Grundy, and colleagues with the Hubble Space Telescope in 2008, and named Gǃòʼé ǃHú.

    Vanth (moon) Moon of 90482 Orcus

    Vanth, full designation (90482) Orcus I Vanth, is the single known natural satellite of the plutino and likely dwarf planet 90482 Orcus. With a diameter of about 440 km, it is half the size of Orcus and probably the third-largest known moon of a known trans-Neptunian object, after Pluto I Charon and Eris I Dysnomia, though it is possible that the poorly resolved Varda I Ilmarë or Haumea I Hiʻiaka might be comparable in size. Vanth was discovered by Michael Brown and T.-A. Suer using discovery images taken by the Hubble Space Telescope on 13 November 2005. The discovery was announced in an IAU Circular notice published on 22 February 2007.

    66652 Borasisi

    66652 Borasisi, or as a binary (66652) Borasisi-Pabu, is a binary classical Kuiper belt object. It was discovered in September 1999 by Chad Trujillo, Jane X. Luu and David C. Jewitt and identified as a binary in 2003 by K. Noll and colleagues using the Hubble Telescope.

    148780 Altjira

    148780 Altjira is a binary classical Kuiper belt object (cubewano). The secondary, S/2007 (148780) 1, is large compared to the primary, 140 kilometres (87 mi) vs. 160 kilometres (99 mi). The Altjiran lightcurve is quite flat (Δmag<0.10), which is indicative of a "quasi-spherical body with a homogeneous surface".

    Ilmarë Moon of 174567 Varda

    Ilmarë, or Varda I, full designation 174567 Varda I Ilmarë, is the single known natural satellite of the Kuiper Belt planetoid 174567 Varda. It was discovered by Keith Noll et al. in 2009, at a separation of about 0.12 arcsec, using discovery images taken by the Hubble Space Telescope on 26 April 2009, and reported in 2011. At approximately 326 km in diameter (about 45% that of its primary), it is the fourth or fifth-largest known moon of a trans-Neptunian object, after Pluto I Charon, Eris I Dysnomia, Orcus I Vanth and very possibly Haumea I Hiʻiaka. Assuming that Ilmarë has the same albedo and density as Varda, Ilmarë would constitute approximately 8.4% of the system mass, approximately 2.2×1019 kg.

    <span class="nowrap">(524366) 2001 XR<sub>254</sub></span>

    (524366) 2001 XR254, provisional designation 2001 XR254, is a trans-Neptunian object and binary system from the classical Kuiper belt, located in the outermost region of the Solar System. The cubewano belongs to the cold population and measures approximately 171 kilometers (110 miles). It was first observed on 10 December 2001, by astronomers at the Mauna Kea Observatory, Hawaii. Its 140-kilometer sized companion was discovered by the Hubble Space Telescope in June 2006.

    <span class="nowrap">(275809) 2001 QY<sub>297</sub></span>

    (275809) 2001 QY297 is a trans-Neptunian object from the classical Kuiper belt, located in the outermost region of the Solar System. The binary classical Kuiper belt object belongs to the cold population.

    References

    1. 1 2 Grundy, W. M.; Noll, K. S.; Roe, H. G.; Buie, M. W.; Porter, S. B.; Parker, A. H.; Nesvorný, D.; Benecchi, S. D.; Stephens, D. C.; Trujillo, C. A. (2019). "Mutual Orbit Orientations of Transneptunian Binaries" (PDF). Icarus. 334: 62–78. Bibcode:2019Icar..334...62G. doi:10.1016/j.icarus.2019.03.035. ISSN   0019-1035 . Retrieved 2019-10-26.
    2. Brown, Michael E.; Butler, Bryan J. (2018-09-18). "Medium-sized satellites of large Kuiper belt objects". The Astronomical Journal. 156 (4): 164. arXiv: 1801.07221 . Bibcode:2018AJ....156..164B. doi:10.3847/1538-3881/aad9f2.
    3. Sickafoose, A. A.; Bosh, A. S.; Levine, S. E.; Zuluaga, C. A.; Genade, A.; Schindler, K.; Lister, T. A.; Person, M. J. (2019-02-01). "A stellar occultation by Vanth, a satellite of (90482) Orcus". Icarus. 319: 657–668. arXiv: 1810.08977 . Bibcode:2019Icar..319..657S. doi:10.1016/j.icarus.2018.10.016.
    4. Grundy, W.M.; Porter, S.B.; Benecchi, S.D.; Roe, H.G.; Noll, K.S.; Trujillo, C.A.; Thirouin, A.; Stansberry, J.A.; Barker, E.; Levison, H.F. (September 2015). "The mutual orbit, mass, and density of the large transneptunian binary system Varda and Ilmarë". Icarus. 257: 130–138. arXiv: 1505.00510 . Bibcode:2015Icar..257..130G. doi:10.1016/j.icarus.2015.04.036.
    5. "IAUC 8751: (120347) 2004 SB_60; 2006gi, 2006gj; V733 Cep". Cbat.eps.harvard.edu. Archived from the original on 2013-12-03. Retrieved 2014-06-14.
    6. Johnston Archive: (120347) Salacia and Actaea
    7. 1 2 3 4 5 6 Stansberry, J.A.; Grundy, W.M.; Mueller, M.; et al. (2012). "Physical Properties of Trans-Neptunian Binaries (120347) Salacia–Actaea and (42355) Typhon–Echidna". Icarus. 219 (2): 676–688. Bibcode:2012Icar..219..676S. CiteSeerX   10.1.1.398.6675 . doi:10.1016/j.icarus.2012.03.029.
    8. 1 2 Fornasier, S.; Lellouch, E.; Müller, P., T.; et al. (2013). "TNOs are Cool: A survey of the trans-Neptunian region. VIII. Combined Herschel PACS and SPIRE observations of 9 bright targets at 70–500 μm". Astronomy & Astrophysics. 555: A92. arXiv: 1305.0449 . Bibcode:2013A&A...555A..15F. doi:10.1051/0004-6361/201321329.