is apparent then, since V = -GM/R near a gravitating body of mass M and orbital radius R, that seen from a stationary frame, V will be increasing for the region behind M, and decreasing for the region in front of it. However, orbits with lower total energy have shorter periods, and so a body moving slowly on the forward side of a planet will lose energy, fall into a shorter-period orbit, and thus slowly move away, or be "repelled" from it. Bodies moving slowly on the trailing side of the planet will gain energy, rise to a higher, slower, orbit, and thereby fall behind, similarly repelled. Thus a small body can move back and forth between a leading and a trailing position, never approaching too close to the planet that dominates the region. Tadpole orbit See also Trojan (celestial body). Figure 1 above shows shorter orbits around the Lagrangian points and (e.g. the lines close to the blue triangles). These are called tadpole orbits and can be explained in a similar way, except that the asteroid's distance from the Earth does not oscillate as far as the point on the other side of the Sun. As it moves closer to or farther from the Earth, the changing pull of Earth's gravitational field causes it to accelerate or decelerate, causing a change in its orbit known as libration. An example of a tadpole orbit is Polydeuces, a small moon of Saturn which librates around the trailing point relative to a larger moon, Dione. In relation to the orbit of Earth, the asteroid is in a tadpole orbit around the leading point. 2020 VT1 follows a temporary horseshoe orbit with respect to Mars. See also Box orbit Co-orbital moon Halo orbit Interplanetary Transport Network Lissajous orbit Natural satellite Quasi-satellite Temporary satellite References External links Research paper describing Horseshoe orbits. Start at page 105. A good description of 2002 AA29 Co-orbital objects Three-body orbits Orbits