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Lecture 13

AS101 Lecture 13

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Patrick Mc Graw

Lecture 13 4/8/2013 3:29:00 PM Astronomy with non-visible light Spectroscopy Why look at other types of light?  Different types of sources emit different ranges of wavelengths  Cosmic microwave background: o Shows us the last remaining heat from the big bang and gives us clues to the early history of the universe. Radio telescopes:  Reflecting telescopes for radio waves.  Since radio waves have larger wavelengths, we need large mirrors to get good angular resolution. Interferometry:  Another way to improve angular resolution: combine signals from several telescopes. Infrared astronomy:  In most ways, infrared optics are not that different from visible light. The problem is that earth’s atmosphere blocks a lot of IR.  IR telescopes also need to be insulated from heat. Spectroscopy: getting more information from light:  We can learn more from light if we understand more about how light interacts with matter: how it is emitted and absorbed.  Spectroscopy: o Breaking light from an object into its different wavelengths, and comparing the amounts of light emitted at different wavelengths. Three basic types of spectra:  Continuous (thermal radiation) o A hot, dense object emits light at all wavelengths at once in a continuous spectrum. o Examples: a standard incandescent light bulb, the sun, a glowing heating coil on the stove, a human body. o This emission is also called blackbody radiation. o The spectrum depends on the temperature. o Stefan-Boltzan Law:  Hotter objects emit more radiation than cooler ones. o Wien’s Law:  Hotter objects emit more protons with a higher average
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