ASTR 101 Lecture 9 Outline of Last Lecture I. Light: The Cosmic MessengerA. Wavelength and FrequencyB. Learning from LightC. Chemical fingerprintsII. Thermal RadiationOutline of Current Lecture I. TelescopesA. Basic Telescope DesignB. Why Put Telescopes Into SpaceII. InterferometryIII. The SunCurrent LectureBasic Telescope Design- Refracting: lenses- Reflecting: mirrors- Most research telescopes today are reflectingBuying 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, portabilityWhy 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 imagesInterferometry- This technique allows two or more small telescopes to work togetherThe Moon would be the best spot for an observatory (but at what price?)CHAPTER 10: The SunWhy 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? .... NOThe sun is powered by NUCLEAR ENERG!Nuclear Potential Energy/Luminosity = 10 billion
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