当前太阳系概述

Our Solar System

What most people know as the Solar System includes the Sun, eight planets (four small rocky interior planets and four outer gas giants), their moons, and the asteroid belt.

The Basic Structure of the Solar System

Johannes Kepler, in 1609 to 1619, published his laws of planetary motion. The first law states that a planetary orbit is an ellipse, and one focus of the ellipse is at the Sun's center. It was proven later that the orbits of all eight planets approximately lie on a single plane, called the ecliptic plane. We see the ecliptic as the path of the sun relative to the stars. This path passes through the 12 zodiac constellations, as well as Ophiuchus. All the planets approximately follow this path - you'll never, for example, see Mars near Ursa Major.

The asteroid belt lies between the orbits of Mars and Jupiter, separating the inner rocky planets from the gas giants beyond. The heliosphere, or the range of the Sun's plasma emission (solar wind) extends to beyond Pluto's orbit. The Oort cloud is a spherical region of radius ~0.8 light-years around the Sun, and home to billions of comets.