| 词条 | Sycorax (moon) |
| 释义 |
| name = Sycorax | image = Sycorax.jpg | caption = Discovery image of Sycorax | discoverer =
| discovered = September 6, 1997 | discovery_ref = {{sfn|Gladman Nicholson et al.|1998|p=}} | mean_orbit_radius = 12,179,000 km | eccentricity = 0.5224 | period = 1288.28 d | inclination = 159° (to the ecliptic){{sfn|Sheppard|Jewitt|Kleyna|2005|p=523|loc=Table 3}} | satellite_of = Uranus | mean_radius = {{val|82.5|18|21}}[2] | surface_area = ~80,000 km² (estimate) | volume = ~2,000,000 km³ (estimate) | mass = ~2.5{{e|18}} kg (estimate) | surface_grav = ~{{Gr|0.0025|82.5}} m/s² (estimate) | escape_velocity = ~{{V2|0.0025|82.5}} km/s (estimate) | density = ~1.3 g/cm³ (assumed) | rotation = 3.6 h[3] | axial_tilt = ? | magnitude = 20.8 (V)[4] | abs_magnitude = {{val|7.83|0.06}}[2] | albedo = {{val|0.049|0.038|0.017}}[2] | single_temperature = ~65 K (estimate) }} Sycorax ({{IPAc-en|ˈ|s|ɪ|k|ər|æ|k|s}} {{Respell|SIK|ər|aks}}) is the largest retrograde 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.{{sfn|Gladman Nicholson et al.|1998|p=}} Officially confirmed as Uranus XVII, it was named after Sycorax, Caliban's mother in William Shakespeare's play The Tempest. OrbitSycorax follows a distant orbit, more than 20 times further from Uranus than the furthest regular moon, Oberon.{{sfn|Gladman Nicholson et al.|1998|p=}} 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.{{sfn|Grav|Holman|Fraser|2004|p=}} 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 characteristicsThe diameter of Sycorax is estimated at 165 km based on the thermal emission data from Spitzer and Herschel Space telescopes[2] 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 {{nowrap|B–V {{=}} 0.87}} {{nowrap|V–R {{=}} 0.44}},{{sfn|Rettig|Walsh|Consolmagno|2001|p=}} {{nowrap|B–V {{=}} 0.78 ± 0.02}} {{nowrap|V–R {{=}} 0.62 ± 0.01}},{{sfn|Grav|Holman|Fraser|2004|p=}} {{nowrap|B–V {{=}} 0.839 ± 0.014}} {{nowrap|V–R {{=}} 0.531 ± 0.005}}[3]), 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{{Clarify|reason=How can it be blue in infrared?|date=January 2019}} and finally becomes neutral at the longer wavelengths.[4] The rotation period of Sycorax is estimated at about 3.6 hours. Rotation causes periodical variations of the visible magnitude with the amplitude of 0.07.[3] OriginIt 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).{{sfn|Sheppard|Jewitt|Kleyna|2005|p=}}[3] See also
References1. ^1 2 3 4 {{cite journal| last1 = Maris| first1 = Michele| last2 = Carraro| first2 = Giovanni| last3 = Parisi| first3 = M.G.| title = Light curves and colours of the faint Uranian irregular satellites Sycorax, Prospero, Stephano, Setebos, and Trinculo| year = 2007| journal = Astronomy & Astrophysics| volume = 472| issue = 1| pages = 311–319| arxiv = 0704.2187| bibcode = 2007A&A...472..311M| doi = 10.1051/0004-6361:20066927}} [1][2][3]2. ^1 2 {{cite journal| last = Romon| first = J.| title = Photometric and spectroscopic observations of Sycorax, satellite of Uranus| year = 2001| journal = Astronomy & Astrophysics| volume = 376| issue = 1| pages = 310–315| doi = 10.1051/0004-6361:20010934| bibcode = 2001A&A...376..310R| author2 = de Bergh, C.| last3 = Barucci| first3 = M.A.| display-authors = 2| last4 = Doressoundiram| first4 = A.| last5 = Cuby| first5 = J.-G.| last6 = Le Bras| first6 = A.| last7 = Douté| first7 = S.| last8 = Schmitt| first8 = B.}} 3. ^1 2 3 4 {{cite journal |last=Lellouch |first=E. |last2=Santos-Sanz |first2=P. |last3=Lacerda |first3=P. |last4=Mommert |first4=M. |last5=Duffard |first5=R. |last6=Ortiz |first6=J. L. |last7=Müller |first7=T. G. |last8=Fornasier |first8=S. |last9=Stansberry |first9=J. |last10=Kiss |first10=Cs. |last11=Vilenius |first11=E. |last12=Mueller |first12=M. |last13=Peixinho |first13=N. |last14=Moreno |first14=R. |last15=Groussin |first15=O. |last16=Delsanti |first16=A. |last17=Harris |first17=A. W. |date=September 2013 |title="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 |url=http://www.aanda.org/articles/aa/pdf/2013/09/aa22047-13.pdf |journal=Astronomy & Astrophysics |publisher= |volume=557 |issue= |pages=A60 |doi=10.1051/0004-6361/201322047 |accessdate=7 November 2014|bibcode = 2013A&A...557A..60L |arxiv=1202.3657 }} }}
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External links{{Commons category|Sycorax (moon)}}
3 : Moons of Uranus|Irregular satellites|Astronomical objects discovered in 1997 |
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