The solar system is a gravitationally bound system of the sun and the orbiting objects around it. The Solar System formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud.
It is located in an outer spiral arm of the Milky Way galaxy. There are eight planets with about 210 known planetary satellites, countless asteroids, comets, meteoroids, and other icy bodies.
The four inner system planets – Mercury, Venus, Earth, and Mars – are called terrestrial planets because of their rocky surfaces. The four giant planets of the outer system – Jupiter, Saturn, Uranus, and Neptune are substantially more massive than the terrestrials.
