Planets Unit of study on the nine planets of our solar system. Tools A B orbit Path of a celestial body as it revolves around another body. asteroid Celestial bodies that revolve around the sun. Most live between Jupiter and Mars. Saturn Second largest planet. It has rings around it. Venus The second planet from the sun. Mars The fourth planet from the sun. Uranus The seventh planet from the sun. Pluto The furthest planet from the sun. The smallest planet. sun A star that is the center of our planetary system. Neptune Eighth planet from the sun. Earth The only planet that supports life. Mercury Closest planet to the sun. satellite A celestial body that orbits a planet. meteoroid A solid body moving in space. Smaller thatn an asteroid.