Oleg Zabluda's blog
Thursday, April 12, 2018
 
Fully ionized hydrogen/Helium seems to emit blackbody radiation
Fully ionized hydrogen/Helium seems to emit blackbody radiation

1.
"""
Temperature Dependence

The key to understanding stellar spectra is that the degree of ionization for various atoms depends strongly on the temperature, as illustrated in the adjacent figure for hydrogen and helium. These plots show the relative abundance of different ionization states of these two atoms as a function of temperature. Thus, hydrogen is present almost entirely in the form of neutral hydrogen (H I) for temperatures below about 7000 K, but above that temperature there is a rapid transition so that above about 10,000 K the hydrogen is present almost completely as ionized hydrogen (H II). In the region 7000 - 10,000 K the gas is a mixture of H I and H II.

Similar considerations hold for helium, but now there are three possibilities. Below about 12,000 K, helium is present primarily as neutral helium (He I). From that temperature up to about 29,000 K, helium is primarily in the first ionized state (He II), and above about 29,000 K most helium is completely ionized (He III).
"""
http://csep10.phys.utk.edu/OJTA2dev/ojta/c2c/ordinary_stars/harvard/ionization_tl.html

2.
"""
Main-sequence stars vary in surface temperature from approximately 2,000 to 50,000 K, [OZ: O-class main sequence stars are >30,000K and they are blackbody]
"""
https://en.wikipedia.org/wiki/Stellar_classification#Harvard_spectral_classification
https://en.wikipedia.org/wiki/Stellar_classification#Harvard_spectral_classification

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