On a dark clear night, the sky looks quiet and peaceful. The stars appear as little pinpoints of light on a cold black canvas. The Sun is the only star in the Solar System, but is one of over 100 billion stars in the galaxy we call the Milky Way. Our Solar System is located about 2/3 of the way out from the galaxy’s center. Astronomers think that most of the stars in the Milky Way galaxy could also have planets orbiting around them. These are called "extra-solar planets".
Why Do We Call Them Planets?
Originally, planets meant wandering stars, named by the Greeks for the stars that move slightly from night to night relative to the background of fixed stars. The reason they wander is that their positions relative to Earth are always changing as they orbit the Sun. Since moons, asteroids, comets, and other objects move in a similar way, the name planet has been reserved for the largest objects orbiting the Sun. Sorry Pluto.
Activities
Our Place in Space
Near/Far
Small/Large
