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is a gateway to astronomy and space science resources. Find lessons on auroras, comets, satellites, satellite images of earth, properties of light, Venus, weather on Mars, solar cycle, tracking orbiting spacecraft, classifying galaxies, calculating rotation rates of planets, sunspots, interstellar medium, and electromagnetic radiation. Learn about basic astrophysics research techniques and how satellites "see" the universe at different wavelengths. (Center for Science Education, National Aeronautics and Space Administration)
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The vast spaces between stars in a galaxy is not completely empty, it is sparsely sprinkled with gas and dust. This 'stuff' between the stars is known as the Interstellar Medium. About 99% of the ISM is hydrogen and helium gas; the remaining 1% consists of gases and dust of heavier elements. The gas is extremely dilute, with an average density of about 1 atom per cubic centimeter. |
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Water-ice clouds on Mars |
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