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Download We live in a solar system that consists of a star we call the Sun and
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Our Solar System We live in a solar system that consists of a star we call the Sun and nine planets and their moons plus numerous comets, asteroids and meteoroids. Our solar system is part of the Milky Way, a galaxy made up of billions of stars, and just one of billions of galaxies known to be traveling through intergalactic space. ORDER OF PLANETS FROM THE SUN AND COMPARATIVE PLANET SIZES MERCURY Smallest planet in our solar system. 0.39 AU. EARTH The only livable planet in our solar system. 1.0 AU. JUPITER Largest planet in our solar system. Over a thousand times larger than Earth. 5.2 AU. NEPTUNE Extremely cold. 30.1 AU. SATURN Lightest planet with many rings. 9.5 AU. SUN VENUS Closest planet to Earth. 0.72 AU. MARS Half the size of Earth, has two moons. 1.5 AU. URANUS Sixty four times the size of Earth. 19.2 AU. PLUTO Actually a dwarf planet and hardly visible even with a powerful telescope. 39.5 AU. DEFINITIONS Asteroid Minor planet. Comets Balls of dusty ice that orbit the Sun. Galaxy A catherine wheel made up from billions of stars which the Sun is one. Meteorite Pieces of rock or metal which strike Earth’s atmosphere. Eclipse When the Moon blocks the sunlight to the Earth (Solar Eclipse) or when the Earth blocks the sunlight to the Moon (Lunar Eclipse). Atmosphere A mixture of gases that surround any celestial body that has a gravitational field. Solar System Made up of planets and moons that orbit a sun. Light Year The distance that light travels in one year, just under ten trillion kilometers. Astronomical Unit (AU) The average distance from the Earth to the Sun. One AU is 149,597,870 kilometers.