Quasi-satellite

A quasi-satellite is an object in a specific type of co-orbital configuration (1:1 orbital resonance) with a planet where the object stays close to that planet over many orbital periods.

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.