Astronomical Figures 190 BC - 120 BC Hipparchus, Astronomer Mathematicians *Devised latitudes and longitudes and created the apparent magnitude scale by d ividing stars into categories according to their brightness (1-6). (It wasn’t until the 1850's that scientists saw the brightest objects in the sky as brighter than first magnitude, so the system now has a rating of zero and negative magnitudes.) In fact, Sirius, the brightest star has a magnitude of -1.46, as seen from Earth. *If the magnitude is higher (fainter) than 6, the naked eye can’t see it. 90 - 168 Ptolemy, Astronomer / Geographer Mathematicians *Wrote the first astronomical account now known as the Almagest (" Mathematical Treatise ") *Ptolemy used Hipparchus's system of epicycles and eccentric circles to explain his geocentric theory of the universe. He believed the planets and sun orbit around the earth. This system became known as the Ptolemaic system. 1473 - 1543 Copernicus, Earth moves around the Sun Christians *Formulated the heliocentric theory that the universe orbits around the sun. 1546 - 1601 Tycho Brahe Mathematicians *Designed and built instruments, he also calibrated them and checked their accuracy periodically. 1564 - 1642 Galileo Galilei, Father of Modern Science Mathematicians *Made improvements to the telescope and astronomical observations, such as the imperfect surface of the Moon, the Phases of Venus, the Moons of Jupiter, and sunspots of the Sun. 1571 - 1630 Johannes Kepler, Laws Planetary Motion Mathematicians *Three laws of planetary motion that bear his name published in 1609 and 1619). 1625 - 1712 Giovanni Cassini, Astronomer Scientists *Determined the obliquity of the ecliptic at 23 deg 29' and studied the effects. 1643 - 1727 Isaac Newton, Theory of Gravitation Alchemists *Worked on optics and gravitation 1656 - 1742 Edmond Halley, Astronomer Mathematicians *mapped out stars and is known because of Haley’s Comet. 1701 - 1744 Anders Celsius, Temperature Scale Inventors *In 1742, he divided the temperature scale of a mercury thermometer at 760mm mercury air pressure into 100 degrees, where 100 is the freezing point and 0 the boiling point of water. 1738 - 1822 Herschel, Discovered Uranus - 1781 Composers *discovered Uranus and infrared radiation. 1811 - 1877 Le Verrier, Co-discovery of Neptune Mathematicians *studied the causes of disturbances in the Solar System. His work led to improved knowledge of the masses of the planets, the scale of the Solar System, and the velocity. 1819 - 1892 John Adams, Discovered Neptune - 1845 Discoveries * predicted the existence of Neptune. 1889 - 1953 Edwin Hubble, Big Bang Theory Mathematicians * devised a classification system for the various galaxies he observed, sorting them by content, distance, shape, and brightness; it was then he noticed redshifts in the emission of light from the galaxies. 1894 - 1966 Lemaître, Proposed Big Bang Theory Christians *proposed what became known as the Big Bang theory. 1905 - 1973 Gerard Kuiper, Astronomer Scientists *considered the father of modern planetary science for his wide ranging studies of the solar system. *established the atmosphere of Saturn's moon, Titan, and discovered Saturn's moon, Miranda, and Neptune's Nereid. Kuiper's prediction of comets traveling near the orbit of Neptune, the Kuiper belt. .