Quasi-satellite
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A quasi-satellite is an object similar to a planet or satellite of the Sun, however its orbit encompasses its planet and the planet's star.
A quasi-satellite's orbit around the Sun takes exactly the same time as the planet's, but has a greater eccentricity. When viewed from the perspective of the planet the quasi-satellite will appear to travel in an oblong loop around the planet, even though it is not technically in orbit around it.
Known quasi-satellites
It is known that Uranus and Neptune can hold satellites for the age of the solar system (about 4.5 billion years), but only 10 million years around Jupiter and 100,000 for Saturn.
It is also known that Earth has quasi-satellites named 2003 YN107 and 2004 GU9, and Venus has the quasi-satellite 2002 VE68.
Objects in "horseshoe orbits" such as 2002 AA29 are also sometimes called quasi-satellites, although this is not the same thing. These "horseshoe" objects occasionally briefly become quasi-satellites for a few decades or a few hundred years before returning to their previous status.
External links
- Quasi-satellite Information Page (http://www.astro.queensu.ca/~wiegert/quasi/quasi.html)
- Earth's New Travelling Companion: Quasi-Satellite Discovered (http://www.space.com/scienceastronomy/earth_asteroid_021021.html)
- Astronomy.com: A new "moon" for Earth (http://www.astronomy.com/asy/default.aspx?c=a&id=2060)
- Discovery of the first quasi-satellite of Venus (http://www.astro.utu.fi/tuorla/new/venusqs.shtml) – University of Turku news release (August 17th, 2004)de:Quasisatellit