|  | 
   
    |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
    | • | Main sequence not quite 
 |  |  
    |  | constant R 
 |  |  
    |  |  
    |  | • | B stars:   R ~10 RSun 
 |  |  
    |  |  |  
    |  |  
    |  | • | M stars:   R ~0.1 RSun 
 |  |  
    |  |  |  
    |  |  
    | • | Betelgeuse: 
    R~ 1,000 RSun 
 |  |  
    |  |  |  
    |  |  
    |  | • | Larger than 1 AU 
 |  |  
    |  |  
    | • | White dwarfs:  R~
    0.01 RSun 
 |  |  
    |  |  |  
    |  |  
    |  | • | A few Earth radii 
 |  |  
    |  |  
    | • | What causes the “main sequence”? 
 |  
    |  |  
    |  | • | Why “similar” size, with 
 |  |  
    |  | precise R related to T? 
 |  |  
    |  |  
    |  | • | Why range of T? 
 |  |  
    |  |  
    | • | Why are a few stars (giants, white 
 |  |  
    |  | dwarfs) not on main sequence? 
 |  |  |  |