Tables 849 and 850 5 4 c 



TABLE 849. — Temperature of Interstellar Space 

 (Eddington, Proc. Roy. Soc, A3, 424, 1926.) 



Total light from stars equivalent to 1000 1st (visual) mag. or heat from about 2000 

 (bolometric) 1st mag. stars. Star abs. mag. 1 radiates 36 X sun = 1.37 X io 35 erg/sec. 

 At std. distance 10 parsecs (3.08 X io 19 cm) gives flow of 1.15 X ICT S erg/cm'Vsec. Energy 

 density due to star app. bolometric mag. 1.0, is 3.8 X icr 16 erg/cm 3 or energy of starlight 

 = 7.7 X 10"" erg/cm 3 . The effective temperature of space from Stefan's law is 3°.2 K. 



In a region away from prepondering influence of a star a black body will take up a tem- 

 perature 3°. 2 K. ; then its radiation will balance that which it absorbs. But if the receiving 

 matter be a strongly selectively absorbing gas, higher temperatures may result. See Fabry., 

 Astrophys. Journ., 45, 264. Then the temperature will be governed by 4 considerations : 

 (1) Line absorption (excitation of atoms) ; energy held about io -8 sec. and then lost by 

 reradiation. An atom meets an electron only once in 5 days. So negligible chance (icr 10 ) 

 of thermal agitation by an encounter. (2) Scattering of free electrons ; retards an electron 

 1 mm/sec./yr— not cumulative and negligible. (3) Continuous absorption during en- 

 counters of electrons with atoms (orbit switches). (4) Photoelectric effect (ionization of 

 atoms). Velocity depends on quality and not intensity of radiation. Forms an electron 

 gas with temperature determined by the mean energy of expulsion. The temperature 

 defined by the mean molecular speed is of the order 10,000° K.* 



The temperature of the electron gas will be the same in space as close to the star. The 

 rate of production of electrons but not their speed will be diminished. The heat of the 

 electrons will be continually renewed and the atoms will gradually be brought to the 

 same temperature. This high temperature is a typical quantum effect. 



* 15,000° K. is considered a better value from more recent data. Plaskett, Fearce, The problems of 

 the diffuse matter in the galaxy, Publ. Dominion Astrophys. Obs., 5, 167, 1923. 



TABLE 850. — Matter and Energy 



(Donnan, Nature, 128, 290, 1931. Dushman, Gen. Elec. Rev., 33, 327, 1930; 

 Eddington, Nature, May 1, 1926.) 



Jeans proposed the annihilation and transformation of an electron and a proton into 

 radiation to account for the immense output of radiation from the stars. Einstein's special 

 relativity theory gives as the energy corresponding to a mass of m grams of matter vie' 

 ergs (c = velocity of light). If £ = energy in ergs, then this transformed to matter 

 =£/c 2 grams. The mass of a proton -f- electron — 6.06 X io 23 g. Applying Einstein's 

 development of Planck's quantum theory, then the coalescence of a proton and electron 

 produces one quantum of monochromatic radiation (photon); and since mc z = ht>, 

 v = 2.2 X io 23 or X = 1.3 X io" 13 cm. Formerly such short waves were not known but the 

 discovery of cosmic rays shows their possibility. 



Now the reaction P + E «=* radiation can occur only under unusual conditions. Imagine 

 a proton-electron gas, only photons of n^iXio'' 1 could change into a matter pair. 

 Donnan shows that the black-body temperature of a hohlraum radiation necessary would 

 be 2.2 X io 120 K. By another method (equation for variation with the temperature of the 



Smithsonian Tables 



