10 42
Irregular galaxies
H-alpha luminosity (ergs/s)
Spiral galaxies
M33
10
40
10 38
10 36
10 34
10
100
1,000
Radius of H II region (light-years)
s k y a n d t e l e s c o p e . c o m * N O V E M B E R 2 0 17
25
Sky and Telescope - November 2017
Table of Contents for the Digital Edition of Sky and Telescope - November 2017