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He first formulates the nebular hypothesis of solar system formation. This hypothesis is the most widely accepted model explaining the formation and evolution of the solar system.
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Johann Palitzsch observes the return of Halley's comet. The interference of Jupiter's orbit had slowed the return by 618 days. Parisian astronomer La Caille suggests it should be named Halley's comet.
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Johann Titius finds the Titius-Bode rule for planetary distances. The Titius–Bode law (sometimes termed just Bode's law) is a hypothesis that the bodies in some orbital systems, including the Sun's, orbit at semi-major axes in a function of planetary sequence. The hypothesis correctly predicted the orbits of Ceres and Uranus, but failed as a predictor of Neptune's orbit.
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William Herschel discovers Uranus during a telescopic survey of the northern sky.
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Pierre Laplace re-states the nebular hypothesis for the formation of the solar system.
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Giuseppe Piazzi discovers the asteroid Ceres.
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Heinrich Wilhelm Olbers discovers the asteroid Pallas.
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Alexis Bouvard detects irregularities in the orbit of Uranus.
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Discovery of the 'Doppler Effect' by Austrian physicist and mathematician, Christian Doppler.
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Samuel Heinrich Schwabe describes the sunspot cycle.
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Johann Galle observes and discovers Neptune. His observations were prompted by mathematical calculations by French astronomer Joseph Leverrier and English astronomer John Couch Adams.
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The beginning of spectral analysis of stars by Sir William Huggins
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Henry Draper takes a photograph of the stellar spectrum of Vega. This is the first of its kind.
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Asaph Hall discovers Phobos and Deimos, the moons of Mars.
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Hertzsprung describes giant and dwarf stars.
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Hertzsprung and Russel introduce H-R diagram that shows how the characteristics of stars are related.
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Hubble shows that galaxies exist outside the Milky Way galaxy.
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Clyde Tombaugh discovers Pluto.
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Discovery of Charon, the moon of Pluto, by James Christy and Robert Harrington
