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Published byGarey Marsh Modified over 9 years ago
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Stars and galaxies
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Constellations Ancient Greeks, Romans and other cultures saw patterns of stars in the sky called constellations They imagined they represented mythological characters, animals or familiar objects. Stars in constellations have no relationship to each other in space.
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Modern constellations The sky is now divided into 88 constellations Many were named by ancient astronomers
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Circumpolar constellations Many constellations circle the North star, Polaris – Big Dipper, Little Dipper, Cepheus, etc. Polaris is directly above the North pole Constellations appear to move because of the Earth’s rotation As Earth orbits the Sun, different constellations come into view. While others disappear (Orion is only seen in winter) Circumpolar const. are visible all year
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Absolute and apparent magnitude some stars seem brighter than others, but that doesn’t mean they are closer to us or are really brighter A star that is very dim might appear bright in the sky if it’s close to Earth, and a star that is very bright might appear dim if it is far away
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Measurement in space Measuring a star’s parallax tells us the distance to stars from our solar system Scientists measure the apparent shift of an object from two different positions. The closer an object is to Earth, the greater the parallax
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We use light years to measure distance in space because space is so huge Light travels 300,000 km/s or about 9.5 trillion km in one year The nearest star to Earth, other than our Sun, is Proxima Centauri, which is 4.3 light years away, or 40 trillion km
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Properties of stars The color of a star tells us its temperature Astronomers study star properties by looking at their spectra. Light from a star passes through a spectroscope which breaks the light into all the colors of the spectrum Dark lines in the spectra tell scientists which elements are in a stars atmosphere
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