 Earth tilts at 23 ° and causes the seasons.  Earth revolves around the Sun.  The moon revolves around the Earth.  Moon reflects the sun’s rays and causes the moon to glow.  Earth is 93,000 million miles from the sun.  The distance from Earth to the sun is called an astronomical unit and measures distances in the solar system.

 Called the terrestrial planets  Made mostly of rock  Mercury: smallest  Venus: lots of clouds; similar in size to Earth  Earth: water planet  Mars : red planet; 7 times smaller than Earth  Asteroid Belts between Mars and Jupiter

 Called Gas Giants  Liquid gases, cold, hydrogen, helium  Jupiter: largest planet  Saturn: rings  Uranus: rings; sideways rotation  Neptune: blue; smallest of the gas giants  Dwarf Pluto = not a planet  Dwarf Ceres = not a planet

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 Contain iron, nickel, and stone  Revolve around the Sun in two main areas. Mars and Jupiter and the Kuiper Belt

 Comets are icy bodies that release gas or dust when heated. Comets' orbits are long, narrow ellipses— more elliptical than any other kind of orbit. They spend a very short amount of time near the Sun, passing very close to it, before swinging out to pass out beyond the orbit of Pluto.  Comets are smaller than planets, moons or asteroids. They are mostly made up of dust particles, frozen water and frozen gases. They are usually very hard to see, but as they approach the Sun, they begin to release gas and dust that are lit up by the sunlight to form huge tails.

 Meteoroids are stone-like or metal-like debris that travels in outer space.  When meteoroids strike the Earth's atmosphere, they burn up in bright streaks called meteors. If any part of the meteor survives and hits the ground, it is called a meteorite.

 Gravity causes the stars to burn  The planets to revolve around the sun.  The moon to revolve around the planets.  The larger the mass the greater the gravitational pull.  Shorter the distance the larger the gravitational pull

 The largest object in the solar system  Average star  Burns hydrogen and Helium: Nuclear Fusion  One of billions of stars in the universe

 Born in a nebula of dust, gases, and gravity causes nuclear fusion  Starts as a protostar.  Burns hydrogen  Stars vary in size, distance temperature, and color  Colors: white, red, blue

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 Galaxies are made up of billions of stars  Three types › Spiral Galaxy  Barred Spiral Galaxy- arm begin to in a straight line  Milky Way › Irregular Galaxy – no pattern › Elliptical Galaxy- flatten round ball  No space, old stars

 The speed that light travels in a year  Used to measure distances outside the solar system.  6 trillion miles or 9 trillion kilometers  Nearest star Proxima Centauri 4.2 light years.  Astronomical Units 93, 000 million miles or 150 million km, the mean distance from Earth to the Sun