Leavitt's findings enabled astronomers such as Ejnar Hertzsprung
and Edwin Hubble to better understand the structure of the universe.
In 1927 the Danish astronomer Ejnar Hertzsprung
(1873-1967; Figure 13), of Hertzsprung-Russell diagram fame, was examining plates in the archives at Harvard College Observatory.
During the early 20th century astronomers Hertzsprung
and Russel independently discovered a correlation between the stellar luminosity (brightness corrected for distance) and spectral class.
Once the Cepheid yardstick (see 1912) had been worked out by Leavitt and Hertzsprung
(see 1905), it became possible to find Cepheids in the globular clusters and determine their distances and the distances of the clusters themselves.
The evolutionary codes compute the corresponding colors, surface brightness, and/or spectral absorption indices emitted by a SSP from the sum of spectra of all stars created and distributed along a Hertzsprung
Russell diagram, weighted with an IMF.
Had he known it, he had to hand in the paper sufficient data to have constructed what would later become known as the Hertzsprung-Russell diagram, several months before Ejnar Hertzsprung
's (1873-1967) first attempt.
The terms were conied by Danish astronomer Ejnar Hertzsprung
had noted that some red stars were giants and some were dwarfs (see 1905), with nothing in between.
The Danish astronomer Ejnar Hertzsprung
(1873-1967) suggested that if a star's distance were known, one could calculate what magnitude it would have if it were some standard distance away.
Halm was soon followed in this concept by Ejnar Hertzsprung
who, in 1919, also established a relationship between these two variables .