What is the satellite for?

Satellite refers to a natural celestial body that runs around the planet and periodically in a closed orbit. Satellites can also be called satellites in general. Man-made satellites are devices built by human beings, which are launched into space by spacecraft such as rockets and space shuttles, and orbit around the earth or other planets like natural satellites. Usually gas planets have many moons.

But if two celestial bodies are of equal mass, the system they form is generally called a two-planet system, not a planet and a natural satellite. Usually, the center of mass of two celestial bodies is within the planet. Therefore, some astronomers believe that Pluto and Pluto should be classified as twin planets, but the discovery of two new Pluto satellites in 2005 made the problem more complicated.

The moon is the most obvious example of a natural satellite. In the solar system, all planets except Mercury and Venus have natural satellites. There are at least 160 known natural satellites in the solar system (including the larger debris that constitutes the planetary ring). Natural satellites are planets orbiting planets and planets orbiting stars. For example, in the solar system, the sun is a star, and planets such as our earth revolve around the sun, while planets such as the moon, Enceladus and Tianwei revolve around our earth. These planets are called natural satellites of planets. Saturn has the second largest number of natural satellites, with 62 known. . Jupiter has the largest number of natural satellites, of which 63 have been confirmed and at least 6 remain to be confirmed. Natural satellites vary in size and are very different from each other. Some of them are only a few kilometers in diameter, such as two small satellites of Mars and some small satellites around Jupiter, Saturn and Uranus. Several of them are larger than Mercury, for example, Titan, Ganymede and Callisto, all of which are over 5,200 kilometers in diameter.

The largest satellites in the solar system (more than 3,000 kilometers) include the Earth's moon, Jupiter's Galileo satellite Io (eo), Europa (Europa), Ganymede, Calisto, Saturn's satellite Titan and Neptune's satellite Triton. For smaller satellites, see the relevant planetary entries.