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There are 95 moons of Jupiter with confirmed orbits as of 23 October 2023. This number does not include a number of meter-sized moonlets thought to be shed from the inner moons, nor hundreds of possible kilometer-sized outer irregular moons that were only briefly captured by telescopes. All together, Jupiter's moons form a satellite system called the Jovian system. The most massive of the moons are the four Galilean moons: Io, Europa, Ganymede, and Callisto, which were independently discovered in 1610 by Galileo Galilei and Simon Marius and were the first objects found to orbit a body that was neither Earth nor the Sun. Much more recently, beginning in 1892, dozens of far smaller Jovian moons have been detected and have received the names of lovers or daughters of the Roman god Jupiter or his Greek equivalent Zeus. The Galilean moons are by far the largest and most massive objects to orbit Jupiter, with the remaining 91 known moons and the rings together composing just 0.003% of the total orbiting mass.
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 were seen through telescopes but not recaptured. 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.
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.
Margaret is the only known prograde irregular satellite of the moons of Uranus. It was discovered by Scott S. Sheppard, et al. in 2003 and given the provisional designation S/2003 U 3.
S/2004 S 7 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 8 March 2005.
S/2004 S 12 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 9 March 2005.
S/2004 S 17 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 13 December 2004 and 5 March 2005.
S/2004 S 13 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 9 March 2005.
The Gallic group is a dynamical grouping of the prograde irregular satellites of Saturn following similar orbits. Their semi-major axes range between 16 and 19 Gm, their inclinations between 36° and 41°, and their eccentricities between 0.46 and 0.53. The International Astronomical Union (IAU) reserves names taken from Gallic mythology for these moons.
S/2006 S 1 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 4 and April 30, 2006. S/2006 S 1 is about 6 kilometres in diameter, and orbits Saturn at an average distance of 18.65 Gm in 951.1 days, at an inclination of 154.6° to the ecliptic, in a retrograde direction and with an eccentricity of 0.0814.
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 eccentric 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.
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 6 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/2007 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 1 May 2007 from observations taken between 18 January and 19 April 2007.
Valetudo, also known as Jupiter LXII and originally known as S/2016 J 2, is an irregular moon of Jupiter. It was discovered by Scott S. Sheppard and his team in data acquired by the 6.5-m Magellan-Baade telescope of the Las Campanas Observatory in 2016, but was not announced until 17 July 2018, via a Minor Planet Electronic Circular from the Minor Planet Center, which also reported the discovery of nine other of Jupiter's moons. Besides data from Las Campanas, the original announcement also referred to data acquired through the 8.1-m Gemini North telescope of the Mauna Kea Observatories as well as the 4.0-m reflector of the Cerro Tololo Inter-American Observatory.
Saturn LX, provisionally known as S/2004 S 29, is a natural satellite of Saturn and a member of the Gallic group. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, and Jan Kleyna on October 7, 2019 from observations taken between December 12, 2004 and January 17, 2007. It was given its permanent designation in August 2021.
S/2018 J 4 is a small outer natural satellite of Jupiter discovered by Scott S. Sheppard on 11 May 2018, using the 4.0-meter Víctor M. Blanco Telescope at Cerro Tololo Observatory, Chile. It was announced by the Minor Planet Center on 20 January 2023, after observations were collected over a long enough time span to confirm the satellite's orbit. The satellite has a diameter of about 2 km (1.2 mi) for an absolute magnitude of 16.7.
S/2019 S 6 is a natural satellite of Saturn. Its discovery was announced by Edward Ashton and Brett J. Gladman on May 8, 2023 from observations taken between July 3, 2019 and July 8, 2021.
S/2006 S 12 is a natural satellite of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, E. Ashton and Brett J. Gladman on May 7, 2023 from observations taken between January 5, 2006 and July 8, 2021.
References
- 1 2 3 4 5 "MPEC 2019-T131 : S/2004 S 24". Minor Planet Electronic Circular. Minor Planet Center. Retrieved 7 October 2019.
- 1 2 3 4 Sheppard, Scott. "Scott S. Sheppard - Saturn Moons". Department of Terrestrial Magnetism. Carnegie Institution for Science. Retrieved 7 October 2019.
- ↑ "M.P.C. 117075" (PDF). Minor Planet Circular. Minor Planet Center. 10 October 2019.
- ↑ "Discovery of 20 new moons gives Saturn a solar system record". National Geographic. Oct 7, 2019. Archived from the original on October 8, 2019. Retrieved Oct 8, 2019.
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