The solar system may be defined as a system including all celestial objects which are subject to the gravitational field of the Sun. According to this definition, the solar system extends over a distance of about 2 light-years, or 0.65 pc, or about 120,000 AU. The most distant frontier that we know is the Oort cloud, a spherical shell that extends beyond about 40,000 AU from the Sun, and is a reservoir for nonperiodic comets. The solar system contains two main regions, the inner solar system between the Sun and the main asteroidal belt and the outer solar system beyond this limit. The inner solar system contains the terrestrial planets and their satellites and several families of asteroids. The outer solar system contains the giant planets and their systems, distant asteroids (Trojans, Centaurs), and trans-Neptunian objects. Most comets spend most of their times in the outer solar system but come in the inner solar system as they approach the Sun.
The solar wind is a flow of...