Experimental ProgRockDan1
HR Diagram

Hertzsprung–Russell Diagram
Verse 1:
HR Diagram
Magnitude
Luinosity
Scatter plot of the Stars

Chorus 1:
Hertzsprung
Russell
Stellar Classification

Verse 2:
Since 1910
Understanding stellar evolution
Effective Temperatures
Color-magnitude (Diagram)

large-scale photographic spectroscopic surveys of stars
Harvard College Observatory
Henry Draper Catalogue.

Unused Lyrics:
Instability strip

More about the HR Diagram:
en.wikipedia.org/wiki/Hertzspr...Russell_diagram