ASTR 101 Lecture 9 Outline of Last Lecture I Light The Cosmic Messenger A Wavelength and Frequency B Learning from Light C Chemical fingerprints II Thermal Radiation Outline of Current Lecture I Telescopes A Basic Telescope Design B Why Put Telescopes Into Space II Interferometry III The Sun Current Lecture Basic Telescope Design Refracting lenses Reflecting mirrors Most research telescopes today are reflecting Buying your own telescope Buy binoculars first you get much more for the same amount of money Ignore the magnification sales pitch Notice aperture size optical quality portability Why do we put telescopes into space It is NOT because they are closer to the stars Recall our 1 to 10 billion scale Sun size of grapefruit Earth size of a tip of a ball point pen 15m from sun Nearest star 4000 km away Hubble orbit microscopically above tip of a ballpoint pen size Earth Turbulence cause twinkling blurs images Interferometry This technique allows two or more small telescopes to work together The Moon would be the best spot for an observatory but at what price CHAPTER 10 The Sun Why does the Sun shine Distance 1 5E8 km Luminosity 3 8E26W Apparent visual magnitude 26 74 Absolute visual magnitude 4 82 Radius 7E5 km 109 X earth Temperature photosphere 5778K center 1 57E7K corona 5E6K Energy from the Sun passes through an imaginary disc that has a diameter equal to the Earth s diameter the flux of energy through the disc is 1370 watts per square meter Is the sun on FIRE NO The sun is powered by NUCLEAR ENERG Nuclear Potential Energy Luminosity 10 billion years
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