| Subject |
has composition |
has definition |
has density |
has synonym |
|---|
| barotropic gas | | A gas in which the pressure is a function of the density only. | | |
| ideal gas | | he pressure of a gas is directly proportional to the product of its temperature and density (p = CρT). The higher the temperature and the more rarefied a gas, the more closely it obeys the ideal gas laws, so the gases in most stars closely approximate ideal gases. For a degenerate gas, the pressure depends only on the density and is independent of the temperature. | | perfect gas |
| interstellar gas | mainly hydrogen | Sparse, cool gas (mainly hydrogen) in interstellar space. Dust absorbs and scatters radiation; gas does not interact directly with radiation but is coupled to the dust by collisions. Interstellar gas affects only light of certain wavelengths. Temperature 10-100 K. | very low | |
| plasma | | A completely ionized gas; the so-called fourth state of matter (besides solid, liquid, and gas) in which the temperature is too high for atoms as such to exist and which consists of free electrons and free atomic nuclei. | | |
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