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Announcements Lunar Eclipse Observing tonight (actually, tomorrow morning) is cancelled due to bad weather. The last scheduled observing night is a week from Wednesday. Additional nights next Tuesday and Thursday have been added. If they are clear, I expect a crowd so I need all the help I can get. We will do the first two that are clear. Dont forget the second project. Presentations are two weeks from Wednesday. I will try to get sample questions for the last exam posted tomorrow or Wednesday

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Astronomy Courses Next Semester (and beyond) Next Semester Astr 2011: Introduction to Observational Astronomy Astr 3005/3006: Observational Astronomy Astr 4010: Astrophysics I Beyond Astr 3020: Cosmology Astr 3040: Astrobiology Astr 4020: Astrophysics II Astr 3030: Astronomical Methods and Instrumentation Astr 4000/4001: Astrophotography

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Where does the Sun get its energy?

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In 1848, Julius Mayer calculated the life of the Sun as a coal burning furnace He came up with only a few thousand years. After that, he suggested the impact of meteorites would keep it hot

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William Thomson, Lord Kelvin, also proposed infalling material To generate enough heat, this would add mass to the Sun, changing the orbital periods of the planets within a few centuries

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Hermann Helmholtz proposed gravitational contraction as a source of energy This would last a few million years but geology said the Earth was at least hundreds of millions of years old

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It would be 1926 before Arthur Eddington proposed that the Sun transmuted hydrogen into helium Eddington didnt know what the precise mechanism was but he knew that, since the mass of four hydrogen atoms is more than the mass of one helium atom, E = mc 2 was the only energy production process that could last long enough.

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It was Hans Bethe who proposed the detailed mechanism of hydrogen fusion in the Sun He won the 1967 Nobel Prize for his work in understanding the process

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As astronomy advanced, better telescopes were needed

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Most 19 th century observatories used a transit circle telescope

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The early reflectors used speculum mirrors: a copper/tin alloy Speculum tarnished easily and required frequent polishing and reshaping

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Justus von Liebig, a chemist, figured out how to metalize a glass blank

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Large achromatic refractors were still being made, though

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The last great refractors were made by Alvan Clark & Sons Using glass blanks made by the Chance Brothers of Birmingham and Feil-Mantois of Paris the Clarks ground the finest refractors ever

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The largest refractor ever made was the 40 at the Yerkes Observatory

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With improved techniques, reflectors were becoming the instrument of choice The 100 Hooker Telescope on Mount Wilson Lassels 40 reflector on Malta

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Solar System Studies Charles Messier was one of the most famous comet hunters but he never followed up on his discoveries to determine the nature of comets

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Giovan Donati was the first to do serious telescopic studies of a comet in 1858

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F. A. Bredikhin compiled descriptions and images of comets and came up with a modest theory

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It wasnt until Fred Whipple in the 1950s that we got a true understanding of comets

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Shooting Stars

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Meteor falls had been observed in history The 1492 Ensisheim fall in Germany was well documented

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Ernst Chlandi speculated that meteorites were leftovers from the formation of the solar system

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The great Meteor Storm of 1833 sparked interest in the study of meteors

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Denison Olmsted figured out the November meteors all seem to come out of Leo

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John Locke and Hubert Newton deduced the radiants for the Aquariads and the Perseids

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John Couch Adams calculated orbits and correlated them to comets The Leonids were from Comet Temple

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The discovery of moons Galileo discovered the major moons of Jupiter in 1610 in some of his first observations using the newly invented telescope Io Europa Ganymede Callisto

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Soon, moons of Saturn were being discovered Titan was discovered by Christiaan Huygens in 1655

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Giovanni Cassini discovered four more Saturnian moons Iapetus in 1671 Rhea in 1672 Dione and Tethys in 1684

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Neptune has one large moon: Triton William Lassell discovered Triton in 1846 only a few weeks after Neptune was discovered

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By 1851 Lassell had discovered two more moons around Uranus Lassell discovered Ariel and Umbriel. Herschel had already discovered Oberon and Titania. Miranda wasnt discovered until 1948. Voyager 2 discovered 10 more moons in 1986. Since then another 11 have been discovered

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Asaph Hall discovered the moons of Mars in 1877 using the USNO 26 refractor

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Giovanni Schiaparelli made detailed observations of Mars in 1877

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He made even more detailed observations during the 1888 opposition

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A mis-translated word set Percival Lowell off in search of Martians

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H. G. Wells picked up on the Martians mania On October 30, 1938 the Mercury Theater broadcast an adaptation of War of the Worlds. Listen to it on the YouTube link.