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The Universe
Term | Definition |
---|---|
Astronomical Unit | A unit of measurement equal to 149.6 million kilometers, the mean distance from the center of the earth to the center of the sun. |
Revolution | A forcible overthrow of a government or social order in favor of a new system. |
Rotation | The action of rotating around an axis or center. |
Solar System | The collection of eight planets and their moons in orbit around the sun, together with smaller bodies in the form of asteroids, meteoroids, and comets. |
Galaxy | A system of millions or billions of stars, together with gas and dust, held together by gravitational attraction. |
Planet | A celestial body moving in an elliptical orbit around a star. |
Light years | A light-year, also light year or lightyear, is an astronomical unit of length equal to just under 10 trillion kilometres. As defined by the International Astronomical Union, a light-year is the distance that light travels in vacuum in one Julian year |
Star | A fixed luminous point in the night sky that is a large, remote incandescent body like the sun. |
Universe | all existing matter and space considered as a whole; the cosmos. The universe is believed to be at least 10 billion light years in diameter and contains a vast number of galaxies; it has been expanding since its creation in the Big Bang about 13 billion. |