'Hertzsprung-Russell, or HR, diagrams are used in, & named for 2 men in, this scientific field'
astronomy
HR: Hertzsprung-Russell, or HR, diagrams are used in, & named for 2 men in, this scientific field
Hertzsprung-Russell, or HR, diagrams are used in, & named for 2 men in, this scientific field
Hertzsprung-Russell, or HR, diagrams are used in, & named for 2 men in, this scientific field
HR
astronomy
HR