﻿COUNTING 
  THE 
  STARS 
  — 
  SEARES 
  

  

  187 
  

  

  Table 
  I. 
  — 
  Mean 
  dislrihuiion 
  of 
  stars 
  

  

  [Number 
  of 
  stars 
  per 
  square 
  degree 
  brighter 
  than 
  photographic 
  magnitude 
  m 
  at 
  different 
  distances 
  from 
  

  

  the 
  Milky 
  Way] 
  

  

  To 
  study 
  these 
  phenomena 
  more 
  closely 
  it 
  is 
  customary 
  to 
  average 
  

   for 
  each 
  limit 
  of 
  brightness 
  all 
  the 
  counts 
  in 
  the 
  Milky 
  Way 
  and 
  tabu- 
  

   late 
  the 
  results; 
  then, 
  similarly, 
  to 
  average 
  and 
  tabulate 
  the 
  counts 
  

   along 
  circles 
  parallel 
  to 
  the 
  Milky 
  Way, 
  on 
  either 
  side 
  and 
  separated 
  

   from 
  it 
  by 
  intervals^ 
  of 
  5° 
  or 
  10°. 
  The 
  result 
  is 
  a 
  "mean 
  distribu- 
  

   tion 
  table" 
  (Table 
  I). 
  The 
  numbers 
  in 
  the 
  first 
  column 
  are 
  the 
  mag- 
  

   nitude 
  limits 
  to 
  which 
  the 
  stars 
  are 
  counted; 
  those 
  in 
  the 
  second, 
  the 
  

   average 
  numbers 
  of 
  stars 
  per 
  square 
  degree 
  in 
  the 
  Milky 
  Way 
  brighter 
  

   than 
  the 
  successive 
  limits, 
  while 
  the 
  following 
  columns 
  give 
  similar 
  

   averages 
  for 
  circles 
  parallel 
  to 
  the 
  Milky 
  Way 
  in 
  latitudes 
  30°, 
  60°, 
  and 
  

   90°.^ 
  

  

  Table 
  I 
  recognizes 
  the 
  symmetrical 
  arrangement 
  of 
  stars 
  on 
  the 
  

   two 
  sides 
  of 
  the 
  Milky 
  Way 
  in 
  that 
  it 
  applies 
  to 
  either 
  side, 
  and, 
  

   in 
  fact, 
  is 
  the 
  average 
  of 
  the 
  counts 
  in 
  the 
  two 
  halves 
  of 
  the 
  sky. 
  

   It 
  shows 
  the 
  rapid 
  increase 
  in 
  the 
  numbers 
  of 
  stars 
  with 
  increasing 
  

   magnitude, 
  the 
  general 
  crowding 
  of 
  the 
  stars 
  toward 
  the 
  Milky 
  

   Way, 
  and 
  now, 
  a 
  third 
  peculiarity, 
  namely, 
  that 
  the 
  crowding 
  is 
  much 
  

   greater 
  for 
  faint 
  stars 
  than 
  for 
  bright 
  ones 
  and 
  increases 
  regularly 
  

   with 
  the 
  limiting 
  brightness. 
  This 
  is 
  revealed 
  by 
  the 
  numbers 
  in 
  

   the 
  last 
  column, 
  which 
  are 
  the 
  ratios 
  of 
  the 
  average 
  counts 
  for 
  latitudes 
  

   0° 
  and 
  90°. 
  Thus 
  the 
  first 
  line 
  of 
  the 
  table 
  shows 
  three 
  and 
  five- 
  

   tenths 
  times 
  as 
  many 
  stars 
  in 
  the 
  Milky 
  Way 
  as 
  at 
  latitude 
  90°; 
  

  

  2 
  Angular 
  distances 
  measured 
  on 
  the 
  sky 
  perpendicular 
  to 
  the 
  great 
  circle 
  through 
  the 
  Milky 
  Way 
  clouds 
  

   (the 
  galactic 
  circle) 
  are 
  called 
  galactic 
  latitudes. 
  Angular 
  distances 
  measured 
  along 
  the 
  galactic 
  circle 
  

   from 
  a 
  certain 
  starting-point 
  are 
  galactic 
  longitudes. 
  These 
  coordinates 
  are 
  analogous 
  to 
  terrestrial 
  latitude 
  

   and 
  longitudes 
  used 
  to 
  define 
  the 
  position 
  of 
  points 
  on 
  the 
  earth. 
  

  

  ' 
  For 
  convenience 
  the 
  logarithms 
  of 
  the 
  numbers, 
  rather 
  than 
  numbers 
  themselves, 
  are 
  often 
  tabulated. 
  

   One 
  square 
  degree 
  is 
  equivalent 
  to 
  about 
  Ave 
  times 
  the 
  area 
  of 
  the 
  skyjcovered 
  by 
  the 
  sun 
  or 
  the 
  full 
  moon. 
  

   For 
  brevity 
  Table 
  I 
  gives 
  results 
  for 
  only 
  four 
  values 
  of 
  the 
  galactic 
  latitude. 
  A 
  more 
  extended 
  table 
  

   may 
  be 
  found 
  in 
  Mt. 
  Wilson 
  Contr. 
  No. 
  301 
  (Table 
  XVII) 
  or 
  in 
  Contr. 
  No. 
  346 
  (Table 
  XIV). 
  

  

  