A satellite is an object that orbits a celestial body periodically in a certain orbit. It can refer to man-made satellites and natural satellites.

Because of the universal gravitation, the surrounding objects are affected by satellites (which can be used to explore extrasolar planets). If two celestial bodies have the same mass, they will usually form a binary system instead of a main star and a satellite. The criterion for judging whether a satellite is a satellite is whether the mass center of two celestial bodies is within one celestial body.

All masses in the solar system, including the earth, are either the satellites of the sun or the satellites of other celestial bodies, such as the moon.

Artificial satellite is a device built by human beings, which is launched into space by space vehicles such as rockets, space shuttles, etc., and orbits the earth or other planets like celestial satellites. If the sun is circling, it can be called an artificial planet.