He befriended fellow students Bart Bok and Pieter Oosterhoff and was taught by Ejnar Hertzsprung, Antonie Pannekoek, Willem de Sitter, Jan Woltjer, Jan Oort and the physicist Paul Ehrenfest.

Ejnar Hertzsprung (, 8 October 1873 – 21 October 1967 ) was a Danish chemist and astronomer.

Using this period-luminosity relation, in 1913 the distance to the SMC was first estimated by Ejnar Hertzsprung.

The term was originally coined in 1906 when the Danish astronomer Ejnar Hertzsprung noticed that the reddest stars — classified as K and M in the Harvard scheme — could be divided into two distinct groups.

In 1935 he became professor at the observatory of the University of Leiden, where Ejnar Hertzsprung was the director.

He was the first student to earn his PhD ( at the age of 22 ) with Ejnar Hertzsprung at Leiden University.

Such a plot was independently developed by Hertzsprung and so it is often called Hertzsprung – Russell diagram.

* Hertzsprung – Russell diagram – Relates absolute magnitude or luminosity versus spectral color or surface temperature.

These color-magnitude plots are known as Hertzsprung – Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell.

In Potsdam in 1906, the Danish astronomer Ejnar Hertzsprung noticed that the reddest stars — classified as K and M in the Harvard scheme — could be divided into two distinct groups.

Of the red stars observed by Hertzsprung, the dwarf stars also followed the spectra-luminosity relationship discovered by Russell.

This name reflected the parallel development of this technique by both Hertzsprung and Russell earlier in the century.

The first color-magnitude diagrams of open clusters were published by Ejnar Hertzsprung in 1911, giving the plot for the Pleiades and Hyades star clusters.

A plot of the temperature of many stars against their luminosities, known as a Hertzsprung – Russell diagram ( H – R diagram ), allows the age and evolutionary state of a star to be determined.

A Hertzsprung – Russell Diagram can be plotted for these clusters which has absolute values known on the luminosity axis.

The PMS star follows a Hayashi track on the Hertzsprung – Russell ( H – R ) diagram.

Hertzsprung – Russell diagram identifying stellar luminosity as a function of temperature for many stars in our solar neighborhood. In astronomy, luminosity is the amount of electromagnetic energy a body radiates per unit of time.

Kuiper finished his doctoral thesis on binary stars with Hertzsprung in 1933, after which he immediately traveled to California to become a fellow under Robert Grant Aitken at the Lick Observatory.

In the period 1911 – 1913, together with Henry Norris Russell, he developed the Hertzsprung – Russell diagram.

From 1919 to 1946 Hertzsprung worked at Leiden Observatory in The Netherlands, from 1937 as director.

The so-called " Hertzsprung – Russell Diagram " has been used ever since as a classification system to explain stellar types and evolution.

Hertzsprung died in Roskilde in 1967.

In 1913, Ejnar Hertzsprung did some work on Cepheids, which needed some revision.

They occupy the top region of the Hertzsprung – Russell diagram.

The various distinctive types of stars are shown by the Hertzsprung – Russell diagram ( H-R diagram ), which is a plot of absolute stellar luminosity versus surface temperature.

Standard theories of stellar evolution hold that the position of a star on the Hertzsprung – Russell diagram should be determined almost entirely by the initial mass of the star and its age.

Heidenstam was born in 1859, of a prosperous family.

Sherlock Holmes, the ancestor of all private eyes, was born during the 1890s.

Henrietta was discovering in the process of writing, as the born writer does, not merely a channel for the discharge of accumulated information but a stimulus to the development of the creative powers of observation, insight and intuition.

She was born Lilian Steichen, her parents immigrants from Luxemburg.

`` My mother read a book right after I was born and there was a Lilian in the book she loved and I became Lilian -- and eventually I became Paula ''.

By now she was sure she was going to have a baby, deciding it would be born in India or Burma that November.

He was born in Savannah, Georgia, in 1909.

About the only time the Hetman seemed excited was when one of his own pet ideas was born.

On April 10, 1904, his first child was born, a son named George after the late Senator.

Modern warfare was born in this campaign -- periscopes, camouflage, booby traps, land mines, extended order, trench raids, foxholes, armored cars, night attacks, flares, sharpshooters in trees, interlaced vines and treetops, which were the forerunners of barbed wire, trip wires to thwart a cavalry charge, which presaged the mine trap, and the general use of anesthetics.

Deppy is Despina Messinesi, a long-time member of the Vogue staff who, although born in Boston, was born there of Greek parents.

Samuel Gorton was born at Gorton, England, near the present city of Manchester, about 1592.

Whether the Fathers, who died before Christ was born of the Virgin Mary, were justified and saved only by the blood which he shed, and the death which he suffered after his incarnation??

Whether the only price of our redemption were not the death of Christ on the cross, with the rest of his sufferings and obediences, in the time of his life here, after he was born of the Virgin Mary??

In the judgment of Chief of Staff Scott it was ironic that the draft policy of a Democratic President, aimed at Germany, had to be pushed through the House of Representatives by the ranking minority member of the Military Affairs Committee -- a Republican Jew born in Germany!!

Thus, the Church was born and because of its intrinsic character was soon identified as a conservative institution, determined to resist the forces of change, to identify itself with the political rulers, and to maintain a kind of splendid isolation from the masses.

And she replied, `` I was born in America, but I was conceived in Vienna ''.

I was born angry.

He kept his attacks on Republicanism for partisan campaigns, but that is part of the game he was born to play.