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lecture16 - 5/7/08 Sun's corona Determining distances to...

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5/7/08 Sun’s corona Determining distances to stars  (parallax) Flux and luminosity Determining stellar masses Watch out for all the crazy units  we’ll use today! (And for all the equations)
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Sun’s Corona Uppermost layer of sun’s  atmosphere: 10 4  – 10 5  km  above photosphere Atoms are extremely hot  and energetic: 10 6  K Very thin: density << 1 kg/ m 3 Thus very dim: only  visible when photosphere  of sun is covered (by  eclipse or disk in  telescope). Emits emission lines in X- ray and UV part of 
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Solar Wind Coronal gas very hot, so atoms move very  quickly Quickly enough to escape Sun’s  gravitational field. Solar wind: electrons, protons (H nuclei),  alpha particles (He nuclei)  
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Stellar Distances How can we measure the distance to a  star? Right now!  Everybody! Hold your thumb  out at arm’s length, and close your left  eye! What does it appear to be in front of? Now, open your left eye and close your  right eye! What’s it in front of now?
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Parallax We look at how the  apparent angular position  of a  nearby object changes from two different vantage  points. This is measuring distance by  parallax . In the example we just did:
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This note was uploaded on 06/11/2008 for the course ASTRO 1 taught by Professor Antonucci during the Spring '08 term at UCSB.

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lecture16 - 5/7/08 Sun's corona Determining distances to...

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