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The Sun is our local star, and it dominates the solar system. The planets, their moons, the asteroids, and comets are all much, much smaller than the Sun. Most of the solar system is empty space.
Earth is one of four rocky planets closest to the Sun. Just beyond them lies the asteroid belt, and farther out, the four gas giant planets. Pluto and other small, icy objects in the Kuiper Belt occupy the distant frontier of the solar system.
The Scale of the Solar System
The major objects in the solar system are very far apart. Astronomers use the 93-million-mile (150-million-kilometer) distance between the Earth and Sun (the astronomical unit) as a unit of measurement. It helps us understand the scale of our solar neighborhood.
Travel times across the solar system depend on the speed you move. Sunlight travels at 186,232 miles (299,833 km) per second. It takes just over 8 minutes to reach Earth and more than an hour to get to Saturn. Our spacecraft (like Voyager, below) move much slower than light speed and take years to reach other planets.