Phoebe (moon)

Phoebe
Cassini image of Phoebe. Jason crater occupies much of the upper image
Discovery
Discovered byW. H. Pickering
Discovery date18 March 1899 (from photos taken 16 August 1898)
Designations
Designation
Saturn IX
Pronunciation/ˈfiːbi/ FEE-bee[1][a]
Named after
Φοίβη Phoíbē
AdjectivesPhoebean /fiːˈbiːən/ fee-BEE-ən[2]
Orbital characteristics[3]
12 960 000 km
Eccentricity0.1562415
550.564636 d
Inclination173.04° (to the ecliptic)
151.78° (to Saturn's equator)
Satellite ofSaturn
GroupNorse group
Physical characteristics
Dimensions(218.8±2.8) × (217.0±1.2) × (203.6±0.6) km[4]
106.5±0.7 km[4][5]
Mass(8.3123±0.0162)×1018 kg[5]
Mean density
1.6428±0.0326 g/cm3[5]
0.038–0.050 m/s2[4]
≈ 0.102 km/s
9.2735 h (9 h 16 min 25 s ± 3 s)[6]
152.14° (to orbit)[7]
Albedo0.100±0.005[8]
Temperature≈ 73(?) K
6.59±0.02[8]

Phoebe (/ˈfiːbi/ FEE-bee) is the most massive irregular satellite of Saturn with a mean diameter of 213 km (132 mi). It was discovered by William Henry Pickering on 18 March 1899[9] from photographic plates that had been taken by DeLisle Stewart starting on 16 August 1898 at the Boyden Station of the Carmen Alto Observatory near Arequipa, Peru. It was the first natural satellite to be discovered photographically.

Phoebe was the first target encountered upon the arrival of the Cassini spacecraft in the Saturn system in 2004, and is thus unusually well-studied for an irregular moon of its size. Cassini's trajectory to Saturn and time of arrival were specifically chosen to permit this flyby.[10] After the encounter and its insertion into orbit, Cassini did not go much beyond the orbit of Iapetus.

Phoebe is roughly spherical and has a differentiated interior. It was spherical and hot early in its history and was battered out of roundness by repeated impacts. There is some evidence that it may be a captured centaur that originated in the Kuiper belt.[11] Phoebe is the second-largest retrograde satellite in the Solar System after Triton.[12]

  1. ^ "Phoebe". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  2. ^ "Phoebean". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  3. ^ "Natural Satellites Ephemeris Service". minorplanetcenter.net.
  4. ^ a b c Thomas, P. C. (July 2010). "Sizes, shapes, and derived properties of the saturnian satellites after the Cassini nominal mission" (PDF). Icarus. 208 (1): 395–401. Bibcode:2010Icar..208..395T. doi:10.1016/j.icarus.2010.01.025. Archived from the original (PDF) on 2011-09-27. Retrieved 2015-09-04.
  5. ^ a b c Jacobson, Robert. A. (1 November 2022). "The Orbits of the Main Saturnian Satellites, the Saturnian System Gravity Field, and the Orientation of Saturn's Pole*". The Astronomical Journal. 164 (5): 199. Bibcode:2022AJ....164..199J. doi:10.3847/1538-3881/ac90c9.
  6. ^ Bauer, J.M.; Buratti, B.J.; Simonelli, D.P.; Owen, W.M. (2004). "Recovering the Rotational Lightcurve of Phoebe". The Astronomical Journal. 610 (1): L57–L60. Bibcode:2004ApJ...610L..57B. doi:10.1086/423131.
  7. ^ Porco CC; et al. (2005-02-25). "Cassini Imaging Science: Initial Results on Phoebe and Iapetus" (PDF). Science. 307 (5713): 1237–1242. Bibcode:2005Sci...307.1237P. doi:10.1126/science.1107981. PMID 15731440. S2CID 20749556. Archived (PDF) from the original on 2018-07-19. Retrieved 2019-09-23.
  8. ^ a b Cite error: The named reference NEOWISE2015 was invoked but never defined (see the help page).
  9. ^ Kovas, Charlie (18 March 1899). "On This Day". What Happened on March 18, 1899. Unknown. Archived from the original on September 12, 2015. Retrieved September 21, 2017.
  10. ^ Martinez, Carolina; Brown, Dwayne (2004-06-09). "Cassini Spacecraft Near First Stop in Historic Saturn Tour". Mission News. NASA. Archived from the original on 2008-06-28. Retrieved 2008-03-02.
  11. ^ Jewitt, David; Haghighipour, Nader (2007). "Irregular Satellites of the Planets: Products of Capture in the Early Solar System" (PDF). Annual Review of Astronomy and Astrophysics. 45 (1): 261–95. arXiv:astro-ph/0703059. Bibcode:2007ARA&A..45..261J. doi:10.1146/annurev.astro.44.051905.092459. S2CID 13282788. Archived from the original (PDF) on 2009-09-19.
  12. ^ "Planetary Satellite Physical Parameters". Archived from the original on 2021-09-04. Retrieved 2020-06-09.


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