Any human-built objects that move orbiting the Earth and other planets in Solar System are called artificial satellite. They are not natural satellites, or what we called moons, that move naturally orbiting planets, dwarf planets, or asteroids. Artificial satellites are built in many purposes; studying Earth and other planets, studying universe, or communicative satellites. Some satellites that are meant for universe study are the International Space Satellite and Space Shuttle.
Soviet Sputnik 1 mission was the first artificial satellite built by humankind. The launch of this satellite in 1957 was then followed by the launches of many satellites by dozens of countries. Today, it is recorded more than 3,000 satellites are operating around the Earth. This is excluded from more than 8,000 space junks; dead satellites or debris going around the Earth too.
