2. The Solar System By Stefanie Blackburn

3. Overview Our Solar System is made up of nine planets, their moons, and our sun. The planets and their moons revolve around, or orbit the sun. Our Solar System The orbits are not round. They are elliptical. Elliptical means egg-shaped. The first four planets are called the inner planets. They are closest to the sun. Their names are Mercury, Venus, Earth and Mars. These planets are made mostly of rock. The next five planets are called the outer planets. Saturn, Jupiter, Uranus and Neptune are called gas giants because they are made mostly of gases. The last planet is called Pluto. It is coated with ice.

4. The Sun Our sun is a star. It is made of gases called hydrogen and helium. It is always burning. The outside of the sun is 11,000 degrees Fahrenheit. All planets get heat and light from this source. All of the planets in our solar system orbit, or revolve, around the sun. That is why we live in the “Solar System.” Our sun is called a yellow dwarf star. It is only a medium-sized star, yet more than one million earths could fit inside. It is four billion years old.

5. Stars Stars are born in cloud formations called nebula, and live for billions of years as huge glowing balls of hot gas. They expand into giant stars which eventually explode and throw off clouds of gases from their outer layers. When stars explode, clouds of helium and other gases from the original stars are formed which, over millions of years, mix with dust and gases, to make the beginnings of new stars. The largest stars have the shortest lives, as they burn hotter and faster than medium-sized and smaller stars. Clusters of stars make formations called constellations. Above is a picture of Betelgeuse.

6. Earth Earth is the third planet from the sun. It is the only planet in our solar system which has liquid water on its surface. About 70% of the surface of Earth is covered by water The only planet in our solar system which has all the conditions that are needed for animals, plants, and humans to live on it.

7. Astrological Phenomenon Comets Comets are small, fragile, irregularly shaped bodies composed mostly of a mixture of water ice, dust, and carbon- and silicon-based compounds. Comets have three distinct parts: a nucleus, a coma, and a tail. Famous cometscomets

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