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PHY121 Ch 7 Notes - Astronomy Chapter 7 The Sun The sun is...

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Astronomy Chapter 7: The Sun - The sun is very bright, and its light and infrared radiation can burn your eyes, so you must take great care in observing it. - The solar atmosphere consists of three layers of hot, low density gas: the photosphere, chromospheres, and corona. - PHOTOSPHERE: [the solar corona] Apparent surface layer of the sun; thin layer of low density gas Depth: 500km Temperature: 5800K Highly opaque Absorbs and emits radiation produced in the solar interior At sunset or sunrise when it is safe to look at the sun, you see the sun’s photosphere, the level from which visible photons most easily escape. Sunspots (dark spots on the sun that contains intense magnetic fields) come and go on the sun, but only rarely are they large enough to be visible to the unaided eye. In photos, the photosphere has a mottled appearance because it’s made of dark- edged regions called granules (each granule lasts 10-20 mins). The overall pattern is called granulation . The granulation of the photosphere is produced by convection currents of hot gas rising from below and cool fluid sinking; Spectra of these granules show that the centers are a few hundred degrees hotter than the edges (centers rising and edges sinking).
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Larger super granules appear to be caused by larger convection currents deeper in the sun; contain about 300 granules each. - CHROMOSPHERE: Region of the sun’s atmosphere just above the photosphere (thin, hot layer of gas) Visible, UV, and X-ray lines from highly ionized gases Temperature increases gradually from 4500K to 10,000K and then jumps to 1 million K The chromosphere is most easily visible during the total solar eclipse, when it flashes Its pink color is caused by the Balmer emission lines in its spectrum. Filtergrams : an image of the sun made using light in one of those dark absorption lines; filtergrams reveal detail in the upper layers of the chromosphere Filtergrams reveal spicules , streams of cooler gas from the photosphere rising up into the chromosphere - CORONA:
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