Sycorax (moon)
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Discovery[1] | |
---|---|
Discovered by | |
Discovery site | Hale Telescope at Palomar Obs. |
Discovery date | 6 September 1997 |
Designations | |
Designation | Uranus XVII |
Pronunciation | /ˈsɪkɒræks/[2][3] |
Named after | Sycorax |
S/1997 U 2 | |
Adjectives | Sycoraxian /sɪkɒˈræksiən/[4] |
Orbital characteristics[5] | |
Epoch 31 July 2016 (JD 2457600.5) | |
Observation arc | 32.37 yr (11,815 d) |
Earliest precovery date | 2 June 1984 |
12,193,230 km (0.0815067 AU) | |
Eccentricity | 0.4841889 |
3.52 yr (1,286.28 d) | |
160.58731° | |
0° 16m 47.56s / day | |
Inclination | 153.22796° (to the ecliptic) 159.403° (to local Laplace plane)[6] |
258.56478° | |
16.29680° | |
Satellite of | Uranus |
Physical characteristics | |
Mean diameter | 157+23 −15 km[7] 165+36 −42 km[8] |
Mass | ~2.5×1018 kg (estimate)[6] |
Mean density | ~1.3 g/cm3 (assumed)[6] |
6.9162±0.0013 hr (double-peaked)[7] 3.6 hr (single-peaked)[9] | |
Albedo | 0.065+0.015 −0.011[7] 0.049+0.038 −0.017[8] |
Temperature | ~65 K (mean estimate) |
20.8 (V)[10] | |
7.5±0.04[7] 7.83±0.06[8] | |
Sycorax /ˈsɪkɒræks/ is the largest irregular satellite of Uranus. Sycorax was discovered on 6 September 1997 by Brett J. Gladman, Philip D. Nicholson, Joseph A. Burns, and John J. Kavelaars using the 200-inch Hale telescope, together with Caliban, and given the temporary designation S/1997 U 2.[1]
Officially confirmed as Uranus XVII, it was named after Sycorax, Caliban's mother in William Shakespeare's play The Tempest.
Orbit[edit]
Sycorax follows a distant orbit, more than 20 times further from Uranus than the furthest regular moon, Oberon.[1] Its orbit is retrograde, moderately inclined and eccentric. The orbital parameters suggest that it may belong, together with Setebos and Prospero, to the same dynamic cluster, suggesting common origin.[11]
The diagram illustrates the orbital parameters of the retrograde irregular satellites of Uranus (in polar co-ordinates) with the eccentricity of the orbits represented by the segments extending from the pericentre to the apocentre.
Physical characteristics[edit]
The diameter of Sycorax is estimated at 165 km based on the thermal emission data from Spitzer and Herschel Space telescopes[8] making it the largest irregular satellite of Uranus, comparable in size with Puck and with Himalia, the biggest irregular satellite of Jupiter.
The satellite appears light-red in the visible spectrum (colour indices B–V = 0.87 V–R = 0.44,[12] B–V = 0.78 ± 0.02 V–R = 0.62 ± 0.01,[11] B–V = 0.839 ± 0.014 V–R = 0.531 ± 0.005[9]), redder than Himalia but still less red than most Kuiper belt objects. However, in the near infrared, the spectrum turns blue between 0.8 and 1.25 μm[clarification needed] and finally becomes neutral at the longer wavelengths.[10]
The rotation period of Sycorax is estimated at 6.9 hours.[7] Rotation causes periodical variations of the visible magnitude with the amplitude of 0.12.[7] The rotation axis of Sycorax is unknown, though measurements of its light curve suggest it is being viewed at a near equator-on configuration. In this case, Sycorax may have a north pole right ascension around 356° and a north pole declination around 45°.[7]
Origin[edit]
It is hypothesized that Sycorax is a captured object; it did not form in the accretion disk which existed around Uranus just after its formation. No exact capture mechanism is known, but capturing a moon requires the dissipation of energy. Possible capture processes include gas drag in the protoplanetary disk and many-body interactions and capture during the fast growth of Uranus's mass (so-called pull-down).[13][9]
See also[edit]
References[edit]
- ^ a b c Gladman Nicholson et al. 1998.
- ^ Shakespeare Recording Society (1995) The Tempest (audio CD)
- ^ Benjamin Smith (1903) The Century Dictionary and Cyclopedia
- ^ Goldberg (2004) Tempest in the Caribbean
- ^ "M.P.C. 102109" (PDF). Minor Planet Circular. Minor Planet Center. 14 November 2016.
- ^ a b c Jacobson, R.A. (2003) URA067 (2007-06-28). "Planetary Satellite Mean Orbital Parameters". JPL/NASA. Retrieved 2008-01-23.
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: CS1 maint: numeric names: authors list (link) - ^ a b c d e f g Farkas-Takács, A.; Kiss, Cs.; Pál, A.; Molnár, L.; Szabó, Gy. M.; Hanyecz, O.; et al. (September 2017). "Properties of the Irregular Satellite System around Uranus Inferred from K2, Herschel, and Spitzer Observations". The Astronomical Journal. 154 (3): 13. arXiv:1706.06837. Bibcode:2017AJ....154..119F. doi:10.3847/1538-3881/aa8365. S2CID 118869078. 119.
- ^ a b c d Lellouch, E.; Santos-Sanz, P.; Lacerda, P.; Mommert, M.; Duffard, R.; Ortiz, J. L.; Müller, T. G.; Fornasier, S.; Stansberry, J.; Kiss, Cs.; Vilenius, E.; Mueller, M.; Peixinho, N.; Moreno, R.; Groussin, O.; Delsanti, A.; Harris, A. W. (September 2013). ""TNOs are Cool": A survey of the trans-Neptunian region. IX. Thermal properties of Kuiper belt objects and Centaurs from combined Herschel and Spitzer observations" (PDF). Astronomy & Astrophysics. 557: A60. arXiv:1202.3657. Bibcode:2013A&A...557A..60L. doi:10.1051/0004-6361/201322047. Retrieved 7 November 2014.
- ^ a b c Maris, Michele; Carraro, Giovanni; Parisi, M.G. (2007). "Light curves and colours of the faint Uranian irregular satellites Sycorax, Prospero, Stephano, Setebos, and Trinculo". Astronomy & Astrophysics. 472 (1): 311–319. arXiv:0704.2187. Bibcode:2007A&A...472..311M. doi:10.1051/0004-6361:20066927. S2CID 12362256.
- ^ a b Romon, J.; de Bergh, C.; et al. (2001). "Photometric and spectroscopic observations of Sycorax, satellite of Uranus". Astronomy & Astrophysics. 376 (1): 310–315. Bibcode:2001A&A...376..310R. doi:10.1051/0004-6361:20010934.
- ^ a b Grav, Holman & Fraser 2004.
- ^ Rettig, Walsh & Consolmagno 2001.
- ^ Sheppard, Jewitt & Kleyna 2005.
- Gladman, B. J.; Nicholson, P. D.; Burns, J. A.; Kavelaars, J. J.; Marsden, B. G.; Williams, G. V.; Offutt, W. B. (1998). "Discovery of two distant irregular moons of Uranus". Nature. 392 (6679): 897–899. Bibcode:1998Natur.392..897G. doi:10.1038/31890. S2CID 4315601.
- Grav, Tommy; Holman, Matthew J.; Fraser, Wesley C. (2004-09-20). "Photometry of Irregular Satellites of Uranus and Neptune". The Astrophysical Journal. 613 (1): L77–L80. arXiv:astro-ph/0405605. Bibcode:2004ApJ...613L..77G. doi:10.1086/424997. S2CID 15706906.
- Sheppard, S. S.; Jewitt, D.; Kleyna, J. (2005). "An Ultradeep Survey for Irregular Satellites of Uranus: Limits to Completeness". The Astronomical Journal. 129 (1): 518–525. arXiv:astro-ph/0410059. Bibcode:2005AJ....129..518S. doi:10.1086/426329. S2CID 18688556.
- Rettig, T. W.; Walsh, K.; Consolmagno, G. (December 2001). "Implied Evolutionary Differences of the Jovian Irregular Satellites from a BVR Color Survey". Icarus. 154 (2): 313–320. Bibcode:2001Icar..154..313R. doi:10.1006/icar.2001.6715.