﻿170 
  ANNUAL 
  EEPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1921 
  

  

  THE 
  PHYSICAL 
  STATE 
  OF 
  STELLAR 
  INTERIORS 
  

  

  What, 
  then, 
  is 
  this 
  mechanism 
  of 
  radiation? 
  And 
  what, 
  as 
  a 
  pre- 
  

   liminary 
  question, 
  is 
  the 
  pli3'sical 
  state 
  of 
  stellar 
  matter? 
  In 
  the 
  

   early 
  days 
  of 
  spectroscopy 
  it 
  AVas 
  commonly 
  supposed, 
  from 
  a 
  faulty 
  

   analogy 
  Avith 
  laboratory 
  experiments, 
  that 
  a 
  hot 
  gas 
  always 
  gave 
  a 
  

   line 
  spectrum, 
  and 
  tliat 
  a 
  continuous 
  spectrum, 
  such 
  as 
  is 
  exhibited 
  

   by 
  the 
  stars, 
  could 
  be 
  emitted 
  only 
  by 
  a 
  solid 
  or 
  a 
  liquid 
  body. 
  It 
  

   is 
  now 
  generally 
  conceded 
  that 
  this 
  view 
  was 
  erroneous, 
  and 
  it 
  is 
  

   recognized 
  that 
  the 
  continuous 
  spectrum 
  of 
  a 
  star 
  merely 
  indicates 
  

   that 
  the 
  star 
  is 
  not 
  transparent, 
  thus 
  leaving 
  the 
  question 
  of 
  stellar 
  

   structure 
  almost 
  entirely 
  ojoen. 
  

  

  The 
  view 
  of 
  stellar 
  structure 
  now 
  universally 
  accepted 
  is 
  that 
  stars 
  

   are 
  formed 
  of 
  matter 
  which, 
  as 
  a 
  consequence 
  of 
  its 
  high 
  tempera- 
  

   ture, 
  is 
  to 
  a 
  very 
  large 
  extent 
  broken 
  up 
  into 
  its 
  constituent 
  electrons 
  

   and 
  nuclei, 
  these 
  all 
  moving 
  about 
  independently 
  like 
  the 
  molecules 
  

   of 
  a 
  gas. 
  The 
  electrostatic 
  attractions 
  wdiich 
  in 
  more 
  peaceful 
  

   surroundings 
  would 
  rapidly 
  unite 
  the 
  wandering 
  nuclei 
  and 
  elec- 
  

   trons 
  into 
  complete 
  atoms 
  and 
  molecules, 
  are 
  powerless 
  in 
  the 
  general 
  

   whirl 
  of 
  rapidly 
  moving 
  projectiles 
  and 
  in 
  face 
  of 
  the 
  shattering 
  

   blows 
  of 
  the 
  quanta 
  of 
  high-frequency 
  radiation 
  which 
  the 
  high 
  

   temperatures 
  of 
  the 
  stellar 
  interiors 
  generate. 
  When 
  I 
  first 
  put 
  

   forward 
  this 
  view 
  in 
  1917 
  (Bakerian 
  Lecture, 
  Phil. 
  Trans., 
  218, 
  p. 
  

   209), 
  I 
  thought 
  it 
  was 
  entirely 
  novel, 
  but 
  I 
  have 
  since 
  found 
  that 
  

   in 
  1644 
  Descartes 
  had 
  conjectured 
  that 
  the 
  sun 
  and 
  fixed 
  stars 
  were 
  

   made 
  of 
  matter 
  "which 
  possesses 
  such 
  violence 
  of 
  agitation 
  that, 
  

   impinging 
  upon 
  other 
  bodies, 
  it 
  gets 
  divided 
  into 
  indefinitely 
  

   minute 
  particles." 
  My 
  own 
  suggestion 
  was 
  not 
  conjecture, 
  being 
  

   based 
  on 
  incontrovertible 
  scientific 
  grounds. 
  In 
  1907 
  Emden 
  

   had 
  published 
  calculations 
  ("Gas 
  Kugeln," 
  p. 
  96) 
  on 
  the 
  in- 
  

   terior 
  states 
  of 
  the 
  sun 
  and 
  stars, 
  in 
  Avhich 
  he 
  assumed 
  the 
  

   stars 
  to 
  be 
  masses 
  of 
  gas 
  resting 
  in 
  an 
  equilibrium 
  similar 
  to 
  that 
  

   of 
  the 
  loAver 
  strata 
  of 
  the 
  earth's 
  atmosphere 
  — 
  the 
  so-called 
  

   " 
  adiabatic 
  " 
  equilibrium 
  in 
  which 
  there 
  are 
  assumed 
  always 
  to 
  be 
  

   sufficient 
  currents 
  to 
  keep 
  the 
  constituent 
  gases 
  thoroughly 
  mixed 
  

   by 
  a 
  process 
  of 
  stirring. 
  On 
  this 
  supposition 
  he 
  found 
  that 
  

   if 
  the 
  sun 
  were 
  composed 
  of 
  air 
  or 
  other 
  diatomic 
  gas 
  of 
  equal 
  

   molecular 
  weight, 
  its 
  central 
  temperature 
  would 
  be 
  455,000,000°, 
  

   while 
  if 
  it 
  consisted 
  of 
  hydrogen, 
  or 
  other 
  diatomic 
  gas 
  of 
  molecular 
  

   weight 
  2, 
  its 
  central 
  temperature 
  would 
  be 
  31,500,000°. 
  These 
  tem- 
  

   peratures 
  are 
  so 
  high 
  that 
  no 
  atom 
  or 
  molecule 
  could 
  survive 
  them; 
  

   at 
  31,500,000° 
  the 
  quantum 
  of 
  radiation 
  has 
  energy 
  2.1 
  X 
  lO""^ 
  ergs, 
  

   which 
  is 
  sufficient 
  to 
  move 
  an 
  electron 
  through 
  a 
  potential 
  difference 
  

   of 
  13,500 
  volts. 
  Even 
  with 
  such 
  quanta 
  flying 
  about, 
  the 
  atomic 
  

   nuclei 
  are 
  still 
  safe, 
  far 
  higher 
  than 
  stellar 
  temperatures 
  being 
  

  

  