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Tarqeq is the slowest-rotating irregular moon measured by Cassini–Huygens, with a period of about 76.13 ± 0.01 h and a roughly ellipsoidal shape. [3] This is very close to a 1:5 resonance with Titan 's orbital period, suggesting that gravitational interactions possibly lock Tarqeq in a mean-motion resonance .
In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter (the combined center of mass) or, if one body is much more massive than the other bodies of the system combined, its speed relative to the center of mass of the most massive body.
In the Solar System, all planets, comets, and asteroids are in such orbits, as are many artificial satellites and pieces of space debris. Moons by contrast are not in a heliocentric orbit but rather orbit their parent object. Geocentric orbit: An orbit around the planet Earth, such as that of the Moon or of artificial satellites.
The Moon's elongation is its angular distance east of the Sun at any time. At new moon, it is zero and the Moon is said to be in conjunction. At full moon, the elongation is 180° and it is said to be in opposition. In both cases, the Moon is in syzygy, that is, the Sun, Moon and Earth are nearly aligned.
This list contains the slowest-rotating minor planets with periods of at least 1000 hours, or 41 2 ⁄ 3 days. See § Potentially slow rotators for minor planets with an insufficiently accurate period—that is, a LCDB quality code of less than 2.
The Moon is Earth's only natural satellite. It orbits at an average distance of 384,400 km (238,900 mi), about 30 times the diameter of Earth. Tidal forces between Earth and the Moon have synchronized the Moon's orbital period (lunar month) with its rotation period at 29.5 Earth days, causing the same side of the Moon to always face Earth.
Most lunar low orbits below 100 km (60 mi) are unstable. [2]Lunar Module Eagle in lunar orbit during Apollo 11, July 1969. Gravitational anomalies slightly distorting the orbits of some Lunar Orbiters led to the discovery of mass concentrations (dubbed mascons) beneath the lunar surface caused by large impacting bodies at some remote time in the past.
Gonggong and its moon Xiangliu, imaged in 2009 and 2010 with Hubble's Wide Field Camera 3 [10]. Following the March 2016 discovery that Gonggong was an unusually slow rotator, the possibility was raised that a satellite may have slowed it down via tidal forces. [3]