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Astr 734 - Order of Magnitude Astrophysics - Fall 2017

Useful constants and conversions

Constants

  • 1 AU = 150 million km = 1.5x1011 m = 500 light-sec = 1.5x1013 cm
  • 1 year = \( \pi \)x107 seconds (pi-ty million)
  • Earth Radius = 6000 km = 6x106 m
  • \( \sigma_T = 6.7 \times 10^{-29} \) m2
  • Proton mass = Neutron mass = 1.7x10-27 kg
  • Electron mass = 9.1x10-31 kg or roughly 10-3 smaller than a proton
  • G = 6.67 x 10-11 m3 / kg / s2 = 0.0043 \( \frac{km}{s} \)2 pc / M_sun

Conversions

  • 1 parsec = 206256 AU
  • 1 radian = 57.296 deg = 206265 arcsec
  • 1 eV = 1.6x10-19 J
  • 1 erg = 10-7 J = 6.2x1011 eV

Formulae

  • Gravitational force FG = GMm/r2
  • Inline latex can be rendered with \( F_G = {GMm \over r^2} \)
  • Display latex can be rendered with

    \[ F_G = {GMm \over r^2} \]

  • Another way to render a latex formula is formula
  • Eddington Luminosity

    \[ L_{\rm{Edd}} = 1.25\times 10^{38} \big(\frac{M}{M_{\rm{Sun}}}\big) \rm{erg}\; \rm s^{-1} = 3.2\times 10^4 \big(\frac{M}{M_{\rm{Sun}}}\big) L_{\rm{Sun}} \]

Data

  • Heat
    • 9 kcal/g = burning fat
    • 4 kcal/g = burning protein
    • 4 kcal/g = burning carbohydrates
    • 1 kcal/g = explosives (TNT)
    • 0.6 kcal/g = boiling water
    • 0.1 kcal/g = heating water (0-100C)
    • 0.08 kcal/g = melting water
  • ISM Densities
    • 1 cm-3 = approximate particle density in Milky Way
    • 10-3 to 10-4 cm-3 = approximate coronal gas (hot ISM) particle density

Class boards

Assignments

Worked examples

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Last modified 24 hours ago Last modified on Dec 13, 2017, 2:44:47 PM

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