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Subsatellite
A subsatellite, also known as a submoon, or moonmoon, is a "moon of a moon" or a hypothetical natural satellite that orbits the moon of a planet. It is inferred from the empirical study of natural satellites in the Solar System that subsatellites may be rare, albeit possible, elements of planetary systems. In the Solar System, the giant planets have large collections of natural satellites. The majority of detected exoplanets are giant planets; at least one, Kepler-1625b, may have a very large exomoon, named Kepler-1625b I, which could theoretically host a subsatellite. Nonetheless, aside from human-launched satellites in temporary lunar orbit, no notable subsatellite is known in the Solar System or beyond. In most cases, the tidal effects of the planet would make such a system unstable. Terminology Terms used in scientific literature for subsatellites include "submoons" and "moon-moons". Colloquial terms that have been suggested include moonitos, moonettes, and moooons. Possible ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Satellite
A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are often colloquially referred to as ''moons'', a derivation from the Moon of Earth. In the Solar System, there are six planetary satellite systems containing 209 known natural satellites altogether. Seven objects commonly considered dwarf planets by astronomers are also known to have natural satellites: , Pluto, Haumea, , Makemake, , and Eris. , there are 442 other minor planets known to have natural satellites. A planet usually has at least around 10,000 times the mass of any natural satellites that orbit it, with a correspondingly much larger diameter. The Earth–Moon system is a unique exception in the Solar System; at 3,474 kilometres (2,158 miles) across, the Moon is 0.273 times the diameter of Earth and about of its mass. The next largest ratios are the Neptune†... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exomoon
An exomoon or extrasolar moon is a natural satellite that orbits an exoplanet or other non-stellar extrasolar body. Exomoons are difficult to detect and confirm using current techniques, and to date there have been no confirmed exomoon detections. However, observations from missions such as ''Kepler'' have observed a number of candidates, in particular around Kepler-1625b, Kepler-1708b, and Kepler-1513b. Two potential exomoons that may orbit rogue planets have also been detected by microlensing. In September 2019, astronomers reported that the observed dimmings of Tabby's Star may have been produced by fragments resulting from the disruption of an orphaned exomoon. Some exomoons may be potential habitats for extraterrestrial life. Definition Although traditional usage implies moons orbit a planet, the discovery of brown dwarfs with planet-sized satellites blurs the distinction between planets and moons, due to the low mass of brown dwarfs. This confusion is resolved ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhea (moon)
Rhea () is the second-largest moon of Saturn and the ninth-largest moon in the Solar System. It is the smallest body in the Solar System for which precise measurements have confirmed a shape consistent with hydrostatic equilibrium. It was discovered in 1672 by Giovanni Domenico Cassini. Discovery Rhea was discovered by Giovanni Domenico Cassini on 23 December 1672. It was the second moon of Saturn that Cassini discovered, and the third moon discovered around Saturn overall. Name Rhea is named after the Titan Rhea of Greek mythology, the "mother of the gods" and wife of Kronos, the Greek counterpart of the god Saturn. It is also designated Saturn V (being the fifth major moon going outward from the planet, after Mimas, Enceladus, Tethys, and Dione). Cassini named the four moons he discovered (Tethys, Dione, Rhea, and Iapetus) '' Sidera Lodoicea'' (the stars of Louis) to honor King Louis XIV. Astronomers fell into the habit of referring to them and Titan as ''S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shepherd Moon
A shepherd moon (also herder moon or watcher moon) is a small natural satellite that clears a gap in planetary-ring material or keeps particles within a ring contained. The name is a result of the fact they limit the "herd" of the ring particles as a shepherd. Due to their gravitational effect, they pick up particles and deflect them from their original orbits through orbital resonance. This causes gaps in the ring system, such as the particularly striking Cassini Division, as well as other characteristic bands, or strange "twisted" deformation of rings. Discovery The existence of shepherd moons was theorized in early 1979. Observations of the rings of Uranus show that they are very thin and well defined, with sharp gaps between rings. To explain this, Goldreich and Tremaine suggested that two small satellites that were undetected at the time might be confining each ring. The first images of shepherd satellites were taken later that year by Voyager 1. Examples Jupiter Sev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iapetus (moon)
Iapetus () is a moon of Saturn. It is the 24th of Saturn’s 83 known moons. With an estimated diameter of 1,469 km, it is the third-largest moon of Saturn and the eleventh-largest in the Solar System. Named after the Titan Iapetus, the moon was discovered in 1671 by Giovanni Domenico Cassini. A relatively low-density body made up mostly of ice, Iapetus is home to several distinctive and unusual features, such as a striking difference in coloration between its leading hemisphere, which is dark, and its trailing hemisphere, which is bright, as well as a massive equatorial ridge running three-quarters of the way around the moon. History Discovery Iapetus was discovered by Giovanni Domenico Cassini, an Italian-born French astronomer, in October 1671. He had discovered it on the western side of Saturn and tried viewing it on the eastern side some months later, but was unsuccessful. This was also the case the following year, when he was again able to observe it on the weste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equatorial Ridge On Iapetus
The equatorial ridge is the tallest mountain feature on Saturn's moon Iapetus. It is high, and is the third tallest mountain structure in the Solar System. It runs along most of Iapetus' equator. It was discovered by the '' Cassini'' probe in 2004. The ridge's origin is unknown. There are bright areas on the sides of the equatorial ridge near Iapetus' bright trailing hemisphere, which were already visible in ''Voyager 2'' images appearing like mountains and were nicknamed the "Voyager Mountains". Discovery Iapetus's equatorial ridge was discovered when the ''Cassini'' spacecraft imaged Iapetus on 31 December 2004. Peaks in the ridge rise more than 20 km above the surrounding plains, making them some of the tallest mountains in the Solar System. The ridge forms a complex system including isolated peaks, segments of more than 200 km and sections with three near parallel ridges. Origins Within the bright regions there is no ridge, but there are a series of isolated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kepler-1625b I
Kepler 1625b I, a possible moon of exoplanet Kepler-1625b, may be the first exomoon ever discovered (pending confirmation), and was first indicated after preliminary observations by the Kepler Space Telescope. A more thorough observing campaign by the Hubble Space Telescope took place in October 2017, ultimately leading to a discovery paper published in '' Science Advances'' in early October 2018. Studies related to the discovery of this moon suggest that the host exoplanet is up to several Jupiter masses in size, and the moon is thought to be approximately the mass of Neptune. Like several moons in the Solar System, the large exomoon would theoretically be able to host its own moon, called a subsatellite, in a stable orbit, although no evidence for such a subsatellite has been found. Studies and observations The original paper presented two independent lines of evidence for the exomoon, a transit timing variation indicating a Neptune-mass moon, and a photometric dip in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exomoon Kepler-1625b-i Orbiting Its Planet (artist’s Impression)
An exomoon or extrasolar moon is a natural satellite that orbits an exoplanet or other non-stellar extrasolar body. Exomoons are difficult to detect and confirm using current techniques, and to date there have been no confirmed exomoon detections. However, observations from missions such as '' Kepler'' have observed a number of candidates, in particular around Kepler-1625b, Kepler-1708b, and Kepler-1513b. Two potential exomoons that may orbit rogue planets have also been detected by microlensing. In September 2019, astronomers reported that the observed dimmings of Tabby's Star may have been produced by fragments resulting from the disruption of an orphaned exomoon. Some exomoons may be potential habitats for extraterrestrial life. Definition Although traditional usage implies moons orbit a planet, the discovery of brown dwarfs with planet-sized satellites blurs the distinction between planets and moons, due to the low mass of brown dwarfs. This confusion is res ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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