Wikipedia
The Hertzsprung–Russell diagram, abbreviated H–R diagram or HRD, is a scatter graph of stars showing the relationship between the stars' absolute magnitudes or luminosities versus their spectral classifications or effective temperatures. More simply, it plots each star on a graph measuring the star's brightness against its temperature (color). It does not map any locations of stars.
The diagram was created circa 1910 by Ejnar Hertzsprung and Henry Norris Russell and represents a major step towards an understanding of stellar evolution or "the way in which stars undergo sequences of dynamic and radical changes over time".
Usage examples of "hertzsprung-russell diagram".
You all ought to know what a Hertzsprung-Russell diagram looks like.
Orlando glanced back at the model, which included something like a Hertzsprung-Russell diagram, plotting the evolving distribution of stellar temperatures and luminosities.
Thursday was the night the astrophysics lectures took place, and we would hear all about the Hertzsprung-Russell diagram, or red giants and blue dwarfs or neutron stars, or black holes.
For, as the world tumbles lazily, it is revealed as the Discworld - flat, circular, and carried through space on the back of four elephants who stand on the back of Great A'tuin, the only turtle ever to feature on the Hertzsprung-Russell Diagram, a turtle ten thousand miles long, dusted with the frost of dead comets, meteor-pocked, albedo-eyed.