How many satellites are there in the solar system?

In the solar system, all planets except Mercury and Venus have natural satellites. There are at least 40 known natural satellites (not counting the debris that constitutes the planetary ring). Saturn has the largest number of natural satellites, of which 17 has been confirmed, and at least 5 have yet 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 on Mars and some small satellites outside Jupiter. Several are larger than Mercury, such as Titan, Ganymede and Callisto, all of which are over 5,200 kilometers in diameter. The concept of artificial satellite may have started with 1870. The first artificial satellite officially put into orbit was the "satellite" 1 launched by the former Soviet Union in 1957. Since then, thousands of planes have flown around the earth. Satellites have also been launched into orbit around Venus, Mars and the moon. Satellites are used in scientific research and have become indispensable tools in modern communication, weather forecast, earth resource exploration and military reconnaissance.