﻿204 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1929 
  

  

  based 
  on 
  the 
  distribution 
  of 
  the 
  globular 
  clusters, 
  which 
  places 
  the 
  

   center 
  of 
  the 
  system 
  at 
  a 
  distance 
  of 
  50,000 
  to 
  60,000 
  light 
  years 
  in 
  the 
  

   direction 
  of 
  longitude 
  325°. 
  The 
  close 
  agreement 
  of 
  the 
  longitude 
  with 
  

   that 
  found 
  from 
  star 
  counts 
  supports 
  the 
  belief 
  that 
  the 
  clusters 
  also 
  

   correctly 
  indicate 
  the 
  distance 
  to 
  the 
  center. 
  If 
  the 
  diameter 
  of 
  the 
  

   system 
  may 
  be 
  regarded 
  as 
  of 
  the 
  order 
  of 
  two 
  or 
  three 
  hundred 
  

   thousand 
  light 
  years, 
  as 
  suggested 
  above, 
  we 
  should 
  then 
  find 
  ourselves 
  

   something 
  like 
  half-way 
  out 
  toward 
  the 
  edge 
  of 
  the 
  system. 
  

  

  But 
  where 
  does 
  the 
  local 
  system, 
  which 
  so 
  dominates 
  the 
  situation 
  

   about 
  us, 
  fit 
  into 
  the 
  picture? 
  It 
  is, 
  perhaps, 
  only 
  an 
  exceptionally 
  

   large 
  aggregation 
  of 
  stars 
  similar 
  to 
  those 
  scattered 
  along 
  the 
  arms 
  

   of 
  the 
  spiral 
  nebulae 
  ; 
  or 
  it 
  may 
  be 
  a 
  more 
  or 
  less 
  independent 
  organiza- 
  

   tion 
  of 
  stars 
  entangled 
  within 
  the 
  larger 
  system 
  — 
  instances 
  of 
  the 
  close 
  

   juxtaposition 
  of 
  two 
  spirals, 
  for 
  example, 
  are 
  not 
  unknown; 
  but 
  per- 
  

   haps 
  the 
  only 
  safe 
  conclusion 
  at 
  present 
  is 
  that 
  a 
  local 
  system 
  of 
  un- 
  

   expected 
  richness 
  and 
  size 
  exists. 
  The 
  members 
  of 
  this 
  system 
  are 
  

   numerous 
  enough 
  to 
  impress 
  something 
  of 
  their 
  own 
  characteristics 
  

   on 
  the 
  distribution 
  of 
  the 
  stars 
  as 
  a 
  whole 
  down 
  to 
  a 
  low 
  limit 
  of 
  

   brightness, 
  and 
  are 
  therefore 
  certainly 
  to 
  be 
  counted 
  by 
  millions. 
  

   In 
  so 
  large 
  a 
  collection 
  it 
  is 
  natural 
  to 
  expect 
  stellar 
  luminosities 
  and 
  

   spectral 
  types 
  similar 
  to 
  those 
  in 
  the 
  larger 
  systems. 
  This 
  being 
  the 
  

   case, 
  the 
  surprisingly 
  large 
  dimensions 
  found 
  for 
  the 
  local 
  system 
  

   follow 
  as 
  a 
  matter 
  of 
  course. 
  

  

  In 
  closing, 
  a 
  word 
  of 
  caution 
  is 
  to 
  be 
  added 
  : 
  The 
  picture 
  drawn 
  of 
  

   the 
  stellar 
  system 
  is 
  only 
  a 
  sketch 
  in 
  broad 
  outlines. 
  Conclusions 
  

   based 
  solely 
  on 
  star 
  counts 
  may 
  be 
  regarded 
  as 
  reliable, 
  for 
  it 
  is 
  

   probable 
  that 
  the 
  counts 
  rest 
  on 
  a 
  sound 
  photometric 
  system; 
  struc- 
  

   tural 
  features 
  derived 
  from 
  analogies 
  with 
  spiral 
  nebulae 
  are 
  less 
  

   certain 
  but 
  still 
  probable; 
  estimates 
  of 
  dimensions 
  and 
  distances 
  

   are 
  uncertain, 
  and, 
  in 
  some 
  instances, 
  possibly 
  not 
  even 
  of 
  the 
  right 
  

   order 
  of 
  magnitude. 
  Above 
  all, 
  it 
  must 
  not 
  be 
  forgotten 
  that 
  practi- 
  

   cally 
  all 
  the 
  conclusions 
  formulated 
  depend 
  on 
  a 
  study 
  of 
  but 
  two 
  

   characteristics 
  of 
  the 
  stars 
  — 
  the 
  numbers 
  seen 
  in 
  different 
  directions 
  

   in 
  the 
  sky 
  and 
  the 
  totals 
  down 
  to 
  different 
  limits 
  of 
  brightness. 
  This 
  

   restriction 
  accounts 
  in 
  part 
  for 
  the 
  lack 
  of 
  detail 
  in 
  the 
  picture; 
  

   at 
  the 
  same 
  time 
  it 
  may 
  mean 
  that 
  results 
  which 
  now 
  seem 
  well 
  

   established 
  will 
  require 
  modification 
  and 
  readjustment 
  when 
  other 
  

   stellar 
  characteristics 
  have 
  been 
  intensively 
  studied. 
  

  

  