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he suggested that the Earth revolved around the Sun
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classified the stars according to their apparent brigthness
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suggested a geocentric astronomic model, naccording to him the moon, and all the planets orbit the Earth
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published his heliocentric model according to wich the planets revolved around the Sun
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carried out very detailed observation of the planets
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used a telescope for the first time to observe the night sky
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build the first telescope using mirrors instead of lenses
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was a book published by Isaac Newton wich explained the laws governing the movement of the planets
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explained Newton's and predicted the retun of the comet
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on 1781 he discovered Uranus
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measure the distance from a star for the first time using geometric methods
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they discovered Neptune
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allows us to identify substances in the stars
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proved that some of the nebulas seen in the sky are in fact independent galaxies
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discovered the planet Pluto
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the discovery of extra-solar planets
