Caption: Types of plasma located on a log-log plot of electron density versus temperature. The image may NOT be completely reliable or yours truly is somehow reading it wrongly (see item 1 below). Dots showing exactly where the types are located would be a good idea. But whatever its deficiencies, the log-log plot does show the vast range of plasmas in electron density and temperature.

Features:

1. Actually, the plot seems to be unreliable:
   1. The central temperature of the Sun is of order 10**7 K, NOT 10**8 K.

   2. I find it hard to believe that ordinary laser plasmas are as hot as 3*10**6 K. But then laser atoms are NOT in thermodynamic equilibrium internally, and so maybe there is some special sense in which they reach 3*10**6 K.

   3. In the human environment, metals (ordinary metals NOT astro metals) are NOT at nearly 10**4 K.

   Maybe yours truly is somehow reading the plot wrongly. But if so anyone could read it wrongly. In any case cum grano salis.

2. Why are metals (ordinary metals NOT astro metals) on the plot?

   The free electrons in a metal (an ordinary metal NOT an astro metal) plus the ions fixed on their crystal lattice may be considered plasma.

3. Temperature, among other things, is an energy parameter that controls the occupation number of matter.

   This explains why the temperature axis is also given in the energy units electron-volts (eV).

4. The conversion between temperature (considered as, is an energy parameter) in kelvins to temperature in the energy unit electron-volts (eV) is given by the formula

   E = kT = [8.6173324(78)*10**(-5) eV/K]*T ≅ [10**(-4) eV/K]*T ,

   where k is Boltzmann's constant and eV is electron-volt which is a convenient microscopic energy unit.

   Note

   1 eV = [1.602176565(35)*10**(-19) coulombs] *[1 Volt] .