The distance between Earth and Titan, Saturn's largest moon, is never the same. Depending on where Earth and Saturn currently sit in their orbits, the gap ranges from about 1.2 billion kilometers at closest approach to about 1.65 billion kilometers at maximum separation, according to SpaceDaily.
The outlet said Titan does not move erratically. Earth and Saturn simply travel at very different speeds, and the distance between the planets is what SpaceDaily called an arithmetic remainder.
Different orbital speeds
Titan orbits Saturn at an average distance of about 1.2 million kilometers, while Saturn itself sits roughly 1.4 billion kilometers from the Sun, about 9.5 times farther than Earth. Earth completes one orbit of the Sun every year, while Saturn takes nearly 29 and a half years, SpaceDaily noted.
Because of that mismatch, the planets constantly move closer and farther apart. When they are on the same side of the Sun, the distance shrinks to about 1.2 billion kilometers, roughly eight times the Earth-Sun distance. When they are on opposite sides, it grows to about 1.65 billion kilometers, or eleven times that distance.
An elliptical orbit adds a second effect
Saturn's path around the Sun is not a perfect circle. Its elliptical orbit takes it from about 1.35 billion kilometers from the Sun at its closest point to about 1.51 billion kilometers at its farthest, a difference of about 160 million kilometers over its 29-year orbit. SpaceDaily said timing matters too: the closest possible alignment comes when Earth and Saturn share the same side of the Sun as Saturn nears its closest point, while the worst comes when the planets are on opposite sides as Saturn nears its farthest point.
