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Dec 18, 2021
For planetary systems, retrograde motion usually means motion that is opposite to the rotation of the main body, that is, the object that is the center of the system. Asteroids usually have a direct orbit around the sun. At present, of the entire set of asteroids, several dozen are known in retrograde orbits, which received it, most likely due to the gravitational interaction with Jupiter.
The orbit of asteroid 20461 Diorets and its position in the solar system
Such objects include the asteroid Dioretsa, which was discovered in 1999 at an observatory near the city of Socorro (New Mexico, USA). It moves in an orbit characterized by high eccentricity and, most importantly, retrograde motion. To highlight this fact, it was named Dioretsa: an "asteroid" read in reverse order.
The asteroid's orbital period around the Sun is 116 years at a distance of 2.4 to 45.4 AU. In terms of these indicators, the orbit of Diotetsa is similar to the orbit of a comet, which led some researchers to the assumption that Diotetsa is of cometary origin, since comets are more likely to be retrograde than asteroids. The famous Halley's comet, for example, orbits the sun in a retrograde orbit.
In 2008, the first trans-Neptunian object with a retrograde orbit, 2008 KV42, was discovered at the Mauna Kea observatory. At perihelion 2008, KV42 is located slightly further than Uranus's orbit, at a distance of 20.3 AU. from the sun. At the time of discovery, the object was at a distance of 32 AU. from the sun. Object 2008 KV42 makes a revolution around our star in about 300 years. The orbital inclination is 103 °. This unusual (retrograde) orbit suggested that 2008 KV42 entered it from the Oort Cloud.
Another trans-Neptunian object (471325) 2011 KT19, discovered in 2011, attracted the attention of scientists due to the almost perpendicular retrograde motion of the object relative to other planets of the solar system. These circumstances prompted scientists to name the object Niku, which means “rebellious” in Chinese.
Image above: Orbits of trans-Neptunian objects 2008 KV 42 and 2011 KT 19 Orbits of trans-Neptunian objects 2008 KV 42 and 2011 KT 19.
Scientists do not yet have reliable versions regarding the non-standard behavior of these space wanderers. Some researchers associate such anomalies with the gravitational effect of a hypothetical ninth planet, the search for which was unsuccessful. Be that as it may, the study of such objects must continue, as they will help to identify the areas that are the sources of retrograde comets and asteroids, as well as understand the evolution of the outer regions of the solar system.
Source: Moscow Planetarium.
Related links:
ROSCOSMOS Press Release: https://www.roscosmos.ru/33637/
Moscow Planetarium: https://www.roscosmos.ru/tag/moskovskiy-planetariy/
Asteroid: https://www.roscosmos.ru/tag/asteroid/
Comet: https://www.roscosmos.ru/tag/kometa/
Images, Text, Credits: ROSCOSMOS/Moscow Planetarium/Orbiter.ch Aerospace/Roland Berga.
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