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The moons of Saturn are numerous and diverse, ranging from tiny moonlets only tens of meters across to the enormous Titan, which is larger than the planet Mercury. There are 146 moons with confirmed orbits, the most of any planet in the solar system. This number does not include the many thousands of moonlets embedded within Saturn's dense rings, nor hundreds of possible kilometer-sized distant moons that have been observed on single occasions. Seven Saturnian moons are large enough to have collapsed into a relaxed, ellipsoidal shape, though only one or two of those, Titan and possibly Rhea, are currently in hydrostatic equilibrium. Three moons are particularly notable. Titan is the second-largest moon in the Solar System, with a nitrogen-rich Earth-like atmosphere and a landscape featuring river networks and hydrocarbon lakes. Enceladus emits jets of ice from its south-polar region and is covered in a deep layer of snow. Iapetus has contrasting black and white hemispheres as well as an extensive ridge of equatorial mountains among the tallest in the solar system.
Skathi, also named Saturn XXVII and originally spelled Skadi, is a natural satellite of the planet Saturn. Skathi is one of Saturn's irregular moons, in its Norse group of satellites. It was discovered on September 23, 2000, by a team of astronomers led by Brett Gladman. The team announced their discovery on December 7, 2000, along with seven other satellites of Saturn, namely; Tarvos, Ijiraq, Thrymr, Siarnaq, Mundilfari, Erriapus, and Suttungr. The moon was named after Skaði, a figure in Norse mythology, as part of an effort to diversify the largely Greek and Roman names of astronomical objects.
Erriapus, or Saturn XXVIII (28), is a prograde irregular satellite of Saturn. It was discovered by Brett Gladman, John J. Kavelaars and colleagues in 2000, and given the temporary designation S/2000 S 10. It was named Erriapo in August 2003 after Erriapus, a giant in Gaulish mythology; the name was changed from dative Erriapo to nominative Erriapus per IAU conventions in late 2007.
Siarnaq, also designated Saturn XXIX, is the second-largest irregular moon of Saturn. It was discovered on 23 September 2000 by a team of astronomers led by Brett J. Gladman. It was named after the Inuit goddess of the sea, Siarnaq, who is more commonly known as Sedna. Siarnaq is the largest member of Saturn's Inuit group of prograde irregular moons, which orbit far from Saturn in the same direction as the planet's rotation. The moons of the Inuit group are believed to have originated as fragments from the collisional breakup of a larger progenitor moon after it was gravitationally captured into orbit around Saturn several billion years ago. Several other small Inuit group moons share similar orbits to Siarnaq, indicating that the moon had experienced another collision after forming from its progenitor.
Fenrir, or Saturn XLI, is a natural satellite of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, and Brian G. Marsden on May 4, 2005, from observations taken between December 13, 2004, and March 5, 2005. Fenrir has an apparent magnitude of 25, making it one of the faintest known moons in the Solar System, and was discovered using some of the largest telescopes in the world. It is even too dark to have been observed by the Cassini spacecraft when it was in orbit around Saturn, for which it never got brighter than approximately 17th apparent magnitude. Fenrir was named after Fenrisulfr, a giant wolf from Norse mythology, father of Hati and Skoll, son of Loki, destined to break its bonds for Ragnarök.
Hati or Saturn XLIII is a natural satellite of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, and Brian G. Marsden on 4 May 2005, from observations taken between 12 December 2004 and 11 March 2005.
Bestla or Saturn XXXIX is a retrograde irregular moon of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, and Brian G. Marsden on 4 May 2005, from observations taken between 13 December 2004 and 5 March 2005.
The Norse group is a large group of retrograde irregular satellites of Saturn. Their semi-major axes range between 12 and 27 Gm, their inclinations between 136° and 178° and their eccentricities between 0.06 and 0.63. Unlike the Inuit and Gallic groups, the orbital parameters are widely dispersed and the group is likely to be composed from a number of subgroups with more homogeneous orbital and physical parameters. The International Astronomical Union (IAU) reserves names taken from Norse mythology for these moons. The exception is Phoebe, the largest, which was discovered long before the others.
S/2006 S 3 is a natural satellite of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, and Brian G. Marsden on June 26, 2006 from observations taken between January and April 2006.
In astronomy, an irregular moon, irregular satellite, or irregular natural satellite is a natural satellite following a distant, inclined, and often highly elliptical and retrograde orbit. They have been captured by their parent planet, unlike regular satellites, which formed in orbit around them. Irregular moons have a stable orbit, unlike temporary satellites which often have similarly irregular orbits but will eventually depart. The term does not refer to shape; Triton, for example, is a round moon but is considered irregular due to its orbit and origins.
S/2007 S 2 is a natural satellite of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, and Brian G. Marsden on May 1, 2007, from observations taken between January 18 and April 19, 2007. S/2007 S 2 is about 5 kilometres in diameter, and orbits Saturn at an average distance of 16,054,500 kilometres in 759.2 days, at an inclination of 176.65° to the ecliptic, in a retrograde direction and with an eccentricity of 0.237. According to Denk et al. (2018), it is presumably at high risk of colliding with Phoebe in the future.
S/2020 S 1 is a natural satellite of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, Edward Ashton, Brett J. Gladman, Jean-Marc Petit and Mike Alexandersen on May 3, 2023 from observations taken between December 14, 2004 and July 8, 2021.
S/2007 S 5 is a natural satellite of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, Edward Ashton, Brett J. Gladman, Jean-Marc Petit and Mike Alexandersen on May 3, 2023 from observations taken between January 5, 2005 and July 9, 2021.
S/2019 S 14 is a natural satellite of Saturn. Its discovery was announced by Edward Ashton and Brett J. Gladman on May 10, 2023 from observations taken between July 1, 2019 and July 9, 2021.
S/2020 S 3 is a natural satellite of Saturn. Its discovery was announced by Edward Ashton, Brett J. Gladman, Jean-Marc Petit and Mike Alexandersen on May 5, 2023 from observations taken between July 3, 2019 and July 9, 2021.
S/2020 S 4 is the faintest natural satellite of Saturn. It was discovered by Edward Ashton, Brett J. Gladman, Jean-Marc Petit and Mike Alexandersen on June 24, 2020, and was announced on May 6, 2023 by the IAU Minor Planet Center after observations were collected over a long period of time to confirm the satellite's orbit that were taken between July 1, 2019 and July 9, 2021.
S/2020 S 5 is a natural satellite of Saturn. Its discovery was announced by Edward Ashton, Brett J. Gladman, Jean-Marc Petit and Mike Alexandersen on May 6, 2023 from observations taken between July 3, 2019 and July 9, 2021.
S/2019 S 11 is a natural satellite of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Edward Ashton, Brett J. Gladman, Jean-Marc Petit and Mike Alexandersen on May 8, 2023 from observations taken between January 5, 2005 and August 16, 2020.
S/2005 S 5 is a natural satellite of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, Edward Ashton, Brett J. Gladman, Jean-Marc Petit and Mike Alexandersen on May 10, 2023 from observations taken between March 9, 2005 and July 24, 2020.
S/2006 S 18 is a natural satellite of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, Edward Ashton, Brett J. Gladman, Jean-Marc Petit and Mike Alexandersen on May 15, 2023 from observations taken between December 14, 2004 and July 9, 2021.
References
- ↑ "Planetary Satellite Mean Elements". Jet Propulsion Laboratory. California Institute of Technology. Retrieved 10 May 2023.
- 1 2 "MPEC 2023-J79 : S/2005 S 4". Minor Planet Electronic Circular. Minor Planet Center. Retrieved 10 May 2023.
- ↑ "S/2005 S 4". Tilmann's Web Site. Tilmann Denk. Retrieved 25 December 2023.
- ↑ Grishin, Evgeni (September 2024). "Irregular Fixation II: The orbits of irregular satellites". Monthly Notices of the Royal Astronomical Society. 533 (1): 497–509. arXiv: 2407.05123 . Bibcode:2024MNRAS.533..497G. doi: 10.1093/mnras/stae1752 .