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Proposed Earth orbited the Sun via De Revolutionibus Orbium Coelestium contradicting the long held Ptolomic belief that the Sun orbited the Earth thereby laying the groundwork for Galileo and Kepler.
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Chronicled supernova of 1572 and discovered it had no diurnal parallax proving it lay beyond the Moon, plotted the motion of the comet of 1577, accurately plotted motions of planets used by Kepler after his death.
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Resolved the stars in the Milky Way, discovered sunspots and measured the Sun’s rotation, observed Venus phases, discovered four moons of Jupiter, observed lunar features and measured lunar wobble, supported the Copernican system of planetary movement via his observations.
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Using Brahe’s precise data derived his three laws of planetary elliptical motion, provided explanation of optical image formation through small apertures, the first enunciation of the inverse square law for intensity of illumination.
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Measured Mars and Jupiter rotation periods, first scientific records of zodiacal light, discovered the Cassini division, and investigated atmospheric refraction.
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Astronomer Royal, discovered Omega Centauri, paid for publishing Newton’s Principia, using Newton’ gravitational law predicted the comet of 1682 would return in 76 years, invented the idea of using transits of Mercury and Venus to determine distance to the Sun.
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The discoverer of Uranus and several satellites of Saturn and Uranus, discovered that some double stars orbit each other, discovered infrared radiation, attempted to map the Milky Way’s shape, known for building state-of-the-art telescopes.
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Postulated the solar system evolved from a large flattened cloud of gas, published differential equations describing planetary orbits and tides, determined the masses of Jupiter, Saturn and Uranus, applied probability theory to errors in observations.
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Discovered several comets, searched for missing planet between Mars and Jupiter forecasted by Bode’s Law and discovered Pallas and Vesta suggesting these were fragments of the missing planet, formulated Olber’s Paradox.
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Father of modern astrometry, published first accurate stellar parallax, discovered orbital deflections of Sirius and Procyon from unseen white dwarfs.
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nvented the stellar spectroscope, comparing laboratory and stellar spectra demonstrated that the Orion nebula's pure emission spectra indicated its gaseous nature while Andromeda galaxy had continuous spectra, imaged solar prominences in H Alpha light.
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The first astrophysicist, invented the spectroheliograph allowing photography of solar prominences in daylight, discovered magnetic fields in sunspots, planned and completed the 200-inch Mt. Palomar telescope.
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Studied stellar proper motions and motions of binary stars, using photography studied stellar brightness, compared stellar color ratios, plotted color-magnitude diagram for the Hyades cluster, which evolved to the Hertzsprung-Russell diagram.
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Discovered the Hubble classification of galaxies, using Cepheid variables in M31 and M33 calculated their distances, showed that galaxy distribution was cosmologically uniform, showed galaxies were moving away from us at speeds proportional to their distance
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Proposed supernova could produce cosmic rays and neutron stars, first resolved stars in Andromeda galaxy, defined Population I and II stars and two kinds of Cepheid variables.
