A quasi-satellite's orbit around the Sun takes exactly the same time as the planet's, but has a different eccentricity (usually greater), as shown in the diagram on the right. When viewed from the perspective of the planet, the quasi-satellite will appear to travel in an oblong retrograde loop around the planet..
In contrast to true satellites, quasi-satellite orbits lie outside the planet's Hill sphere, and are unstable. Over time they tend to evolve to other types of resonant motion, where they no longer remain in the planet's neighborhood, then possibly later move back to a quasi-satellite orbit, etc.
Other types of orbit in a 1:1 resonance with the planet include horseshoe orbits and tadpole orbits around the Lagrangian points, but objects in these orbits do not stay near the planet's longitude over many revolutions about the star. Objects in horseshoe orbits are known to sometimes periodically transfer to a relatively short-lived quasi-satellite orbit, and are sometimes confused with them. An example of such an object is 2002 AA29.
The word "geosynchronous" is sometimes used to describe quasi-satellites of the Earth, because their motion around the Sun is synchronized with Earth's. However, this usage is unconventional and confusing. Conventionally, geosynchronous satellites revolve in the prograde sense around the Earth, with orbital periods that are synchronized to the Earth's rotation.
Venus has a quasi-satellite, 2002 VE68. This asteroid is also a Mercury- and Earth-crosser; it seems to have been a "companion" to Venus for the last 7000 years or so only, and is destined to be ejected from this orbital arrangement about 500 years from now.
As of 2016, Earth has several known quasi-satellites: (164207) 2004 GU9, (277810) 2006 FV35, 2013 LX28, 2014 OL339 and (469219) 2016 HO3. 2016 HO3 was discovered in 2016 in a quasi-satellite, and is predicted to be stable in this orbital location for several hundred years, in contrast to 2003 YN107 which departed its near-Earth quasi-satellite position a few years after it was discovered. Earth quasi-satellites tend to stay between 38 and 100 lunar distances.
(309239) 2007 RW10 is a temporary quasi-satellite of Neptune. The object has been a quasi-satellite of Neptune for about 12,500 years and it will remain in that dynamical state for another 12,500 years.
Based on simulations it is believed that Uranus and Neptune could potentially hold quasi-satellites for the age of the Solar System (about 4.5 billion years), but a quasi-satellite's orbit would remain stable for only 10 million years near Jupiter and 100,000 years near Saturn. Jupiter and Saturn are known to have quasi-satellites.
In early 1989, the Soviet Phobos 2 spacecraft was injected into a quasi-satellite orbit around the Martian moon Phobos, with a mean orbital radius of about 100 kilometres (62 mi) from Phobos. According to computations, it could have then stayed trapped in the vicinity of Phobos for many months. The spacecraft was lost due to a malfunction of the on-board control system.
Some objects are known to be accidental quasi-satellites, which means that they are not forced into the configuration by the gravitational influence of the body of which they are quasi-satellites. The minor planets Ceres, Vesta, and Pluto are known to have accidental quasi-satellites. In the case of Pluto, the known accidental quasi-satellite, (15810) 1994 JR1, is, like Pluto, a plutino, and is forced into this configuration by the gravitational influence of Neptune. This dynamical behavior is recurrent, the object becomes a quasi-satellite of Pluto every 2.4 Myr and remains in that configuration for nearly 350,000 years.
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