What is the H-R Diagram?
The H-R Diagram, the most famous diagram in astronomy, was named after two names of Dutch astronomers, Heinrich Hertzprung (1873-1967) and an astronomer from Princeton, Henry Norris Russel (1877-1957). Before the first World War, the astronomers independently studied that the obvious type of stars are distinguished when they are arranged by essential brightness, color and temperature. Most stars are not dispersed on the diagram. The stars are on the diagonal in order of connection from the cold misty red stars at the right lower corner to the heated light-blue stars and white stars at the left upper corner. The diagonal is the Main Sequence. However, it is not to say all of the stars on the Main Sequence. There are few very shiny stars yet they are very big. Such stars are located at right upper corner on the diagram. According to this knowledge, the white stars at lower left corner must be dusky and very small. There is no explanation why the white high-temperature stars are dusky and
