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* Hertzsprung – Russell diagram – Relates absolute magnitude or luminosity versus spectral color or surface temperature.
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Hertzsprung and –
These color-magnitude plots are known as Hertzsprung – Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell.
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.
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.
In the period 1911 – 1913, together with Henry Norris Russell, he developed the Hertzsprung – Russell diagram.
The so-called " Hertzsprung – Russell Diagram " has been used ever since as a classification system to explain stellar types and evolution.
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.
* Hertzsprung – Russell diagram ( H-R diagram or HRD, also known as a colour-magnitude diagram or CMD ), used in understanding stellar evolution in astronomy and astrophysics
In the standard Hertzsprung – Russell diagram, blue giants are found in the upper left corner, due to their high luminosity and early spectral type.
Apart from this, because of their large radii and luminosities, giant stars lie above the main sequence ( luminosity class V in the Yerkes spectral classification ) on the Hertzsprung – Russell diagram and correspond to luminosity classes II or III.
During this portion of its evolution, labeled the subgiant branch on the Hertzsprung – Russell diagram, the luminosity of the star remains approximately constant and its surface temperature decreases.
Hertzsprung and Russell
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.
* 1910 — Ejnar Hertzsprung and Henry Norris Russell study the relation between magnitudes and spectral types of stars
Hertzsprung and diagram
If not very massive, it may be found in the horizontal branch on the Hertzsprung – Russell diagram, or its position in the diagram may move in loops .< sup >, chapter 6 .</ sup > If the star is not heavier than approximately 8 solar masses, it will eventually exhaust the helium at its core and begin to fuse helium in a shell around the core.
It will then increase in luminosity again as, now an AGB star, it ascends the asymptotic giant branch of the Hertzsprung – Russell diagram.
Hertzsprung and absolute
These are stars that have an unusually low absolute magnitude for their spectral class, lying well below the main sequence on the Hertzsprung – Russell diagram of stellar temperature vs. luminosity.
Hertzsprung and luminosity
The effective temperature and the bolometric luminosity are the two fundamental physical parameters needed to place a star on the Hertzsprung – Russell diagram.
Overall luminosity changes little during the subgiant stage, as shown by a more or less horizontal evolution off the immediate main sequence ; this feature is prominent in Hertzsprung – Russell diagrams of globular clusters, as the lateral extension after the turnoff point but before the " ascent " to red giant status.
These stars are more luminous than main sequence stars of the same surface temperature ( or colder than main sequence stars of comparable luminosity ), or above and to the right of the main sequence on the Hertzsprung – Russell diagram.
Hertzsprung and .
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.
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.
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.
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.
From 1919 to 1946 Hertzsprung worked at Leiden Observatory in The Netherlands, from 1937 as director.
Using this period-luminosity relation, in 1913 the distance to the SMC was first estimated by Ejnar Hertzsprung.
– and Russell
Bertrand Russell, the first to discuss the paradox in print, attributed it to G. G. Berry ( 1867 – 1928 ), a junior librarian at Oxford's Bodleian library, who had suggested the more limited paradox arising from the expression " the first undefinable ordinal ".
* 1910 – Russell Lynes, American art historian, photographer, author and managing editor of Harper's Magazine ( d. 1991 )
Fellow critic James Russell Lowell called him " the most discriminating, philosophical, and fearless critic upon imaginative works who has written in America ", suggesting – rhetorically – that he occasionally used prussic acid instead of ink.