The sun is at the center of the solar system and has a temperature of 15 million degrees Celsius with a diameter of 1.4 million km. It produces light and heat through nuclear fusion in its core. Mercury, Venus, Earth, and Mars are the inner, solid planets, while Jupiter, Saturn, Uranus and Neptune are the outer, gas giants. Key facts are provided about each planet's distance from the sun, composition, temperature, orbit and other characteristics. The document sources its information from Wikipedia, NASA publications and websites, science books, and other people.