Our Solar System

There are perhaps thousands of galaxies in the universe. Each one of these galaxies is a collection of planets, moons, comets, meteors, and asteroids that spin or orbit around a center star. Our galaxy, the Milky Way, orbits around the sun.

Galaxies have been observed that have several different shapes. The three main shapes of galaxies are elliptical, irregular, and spiral. The Milky Way is a spiral galaxy.

There are nine known planets in our solar system. They revolve around the largest star, the sun. The times of these orbits range from less than 3 months for Mercury to 247 years for Pluto.

The closer a planet is to the sun, the warmer its temperature is. Planets near the sun are quite warm, while those farthest away, like Pluto, are very cold because very little of the sun’s rays reach it.

The planets are divided into two main groups: inner and outer planets. The inner planets include Mercury, Venus, Earth, and Mars.  They are smaller planets that are made of rock and iron.

stars and black holes

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Questions and comments: [email protected]  last revised 7/2005