Today in Astronomy 142 - Astro Pas Rochester
Today in Astronomy 142 - Astro Pas Rochester Today in Astronomy 142 - Astro Pas Rochester
Energy sources for the SunChemical energy (burning) doesn’t work.“The Sun is nothing but a burning ember:” Anaxagoras ofClazomenae, ca. 450 BC.Suppose (optimistically) that the Sun were made of anthracitecoal, with enough oxygen to burn it completely to CO 2 :5.5x10 32 gm coal, 1.45x10 33 gm O. Burning 1 gm of anthracitecoal to CO 2 liberates 4.3x10 11 erg. Thus the Sun’s initialenergy reserve would beΔE =4.3x10 11 x 5.5x10 32 erg = 2.4 x 10 44 ergwhich at the Sun’s present luminosity would lastAstronomy 142 28
Energy sources for the Sun (continued)Collapse and liberation of gravitational potential energyalso doesn’t work (Kelvin and Helmholtz, late 19th century):However, mass energy would work, even if only 0.1% of itcould be converted to radiation:Astronomy 142 29
- Page 1 and 2: Today in Astronomy 142More on the S
- Page 3 and 4: In detail:absorption linesare also
- Page 5 and 6: Radiation transportkeeping track of
- Page 7 and 8: Mean free pathκopacity units g -1
- Page 9 and 10: Opacity depends onwavelength becaus
- Page 12 and 13: Solar “granulation:” the tops o
- Page 14 and 15: Using Adaptive Optics to look at de
- Page 16 and 17: Further out: the corona and chromos
- Page 18 and 19: Sunspots: solar magnetismFigure: Ch
- Page 20 and 21: Sunspot progress, activity during s
- Page 22 and 23: 11-year sunspot cycle, for the last
- Page 24 and 25: Sunspot formation and cycle: intera
- Page 26 and 27: Cooling timescaleAstronomy 142 26
- Page 30 and 31: Energy sources for the Sun (continu
Energy sources for the SunChemical energy (burn<strong>in</strong>g) doesn’t work.“The Sun is noth<strong>in</strong>g but a burn<strong>in</strong>g ember:” Anaxagoras ofClazomenae, ca. 450 BC.Suppose (optimistically) that the Sun were made of anthracitecoal, with enough oxygen to burn it completely to CO 2 :5.5x10 32 gm coal, 1.45x10 33 gm O. Burn<strong>in</strong>g 1 gm of anthracitecoal to CO 2 liberates 4.3x10 11 erg. Thus the Sun’s <strong>in</strong>itialenergy reserve would beΔE =4.3x10 11 x 5.5x10 32 erg = 2.4 x 10 44 ergwhich at the Sun’s present lum<strong>in</strong>osity would last<strong><strong>Astro</strong>nomy</strong> <strong>142</strong> 28
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