Harvard Astronomy 201b

CHAPTER: Energy Density Comparison

In Book Chapter on February 6, 2013 at 10:06 pm


See Draine table 1.5 The main kinds of energy present in the ISM are:

  1. The CMB
  2. Thermal IR from dust
  3. Starlight
  4. Thermal kinetic energy (3/2 nKT)
  5. Turbulent kinetic energy (1/2 \rho \sigma_v^2)
  6. B fields (B^2 / 8 \pi)
  7. Cosmic rays

All of these terms have energy densities within an order of magnitude of 1 ~{\rm eV ~ cm}^{-3}. With the exception of the CMB, this is not a coincidence. Because of the dynamic nature of the ISM, these processes are coupled together and thus exchange energy with one another.

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