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The Big Bang probably occurred
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First solar-lunar calendars
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Construction of an observatory in Cairo was begun in 1120 A.D. This is possibly the first observatory built in Medieval Islam. Unfortunately, the patron of the observatory was found guilty of several crimes including communication with Saturn, and was sentenced to death. The observatory was then destroyed in 1125 A.D. and the personnel were forced to flee for their lives
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Eratosthenes measures the circumference of the earth with surprising accuracy!
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Hipparchus develops the first acccurate star map and star catalogue with over 850 of the brightest stars
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Tycho Brahe discovers a supernova in constellation of Cassiopeia.
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Pope Gregory XIII introduces the Gregorian calendar
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Hans Lippershey, a Dutch spectacles maker invents the telescope
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Galileo uses telescope for astronomical purposes. He discovers 4 Jovian moons, the Moon's craters and the Milky Way galaxy.
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Kepler's First and Second Laws of Planetary Motions are announced
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Christian Huygens discovers Saturn's rings and Titan, the fourth satellite of Saturn
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While in Paris, Danish astronomer Ole Romer measures the speed of light.
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Newton publishes his theory of universal gravitation in the work Philosophiae Naturalis Principia Mathematica. This is seen to be the start of Modern Astronomy.
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The discovery of Uranus by Herschel
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Asaph Hall discovers Phobos and Deimos, the moons of Mars.
