The Planets

Which planet is closest to us?
Earth, of course!

Nine planets move, or revolve, around the sun. These planets are all different sizes, are composed, or made of, different things, and their surfaces all look different. These planets move around the sun in a circle called an orbit. Some planets have many different moons, and some have rings around them made of rock and bits of ice. Some of them have ancient volcanoes and at least one has active volcanoes.

Looking up at the night sky, the other planets look like bright stars. When you look through binoculars or a small telescope though, real stars just look brighter. Planets look like disks, or tiny balls. Also, while star patterns or constellations stay the same as they move across the sky, the planets change their position.

To view the solar system and the orbits:

All about the solar sytem

When ancient people watched the night sky, they noticed that five "stars" moved in a different way from the other stars. They called them "planets", the Greek word for "wanderer". Later, after telescopes were invented, three other planets were noticed, bringing the total to nine if we include Earth.

There are basically two types of planets. The Earth-like or "terrestrial" planets - Mercury, Venus, Earth, and Mars - are small and rocky. Mercury is the closest to the Sun and is also the smallest of the inner-planets. It has no real atmosphere. Venus is about the same size as the Earth and has a very thick atmosphere, making the temperature at the surface over 800 degrees. Mars is rocky and smaller then the Earth. Its atmosphere is very thin.

Next come the gas planets or "Jovian" planets - Jupiter, Saturn, Uranus and Neptune. They are giant gas planets, and rotate very fast. The Jovian giants are circled by rings made of tiny chunks of ice and bits of rock. Saturn has the brightest rings. Each of these huge planets has many moons; some of which are larger then the planet Mercury! Finally comes tiny Pluto. It is the smallest planet, smaller then our moon, and the farthest away from the Sun. It is made of ice and rock.