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The Hertzsprung–Russell diagram (abbreviated as H–R diagram, HR diagram or HRD) is a scatter plot of stars showing the relationship between the stars' absolute magnitudes or luminosities and their stellar classifications or effective temperatures.
These are the most numerous true stars in the universe and include the Sun. Color-magnitude plots are known as Hertzsprung–Russell diagrams after Ejnar Hertzsprung and Henry Norris Russell. After condensation and ignition of a star, it generates thermal energy in its dense core region through nuclear fusion of hydrogen into helium. During ...
The Hertzsprung–Russell diagram, which the MK system is based on, is observational in nature so these remnants cannot easily be plotted on the diagram, or cannot be placed at all. Old neutron stars are relatively small and cold, and would fall on the far right side of the diagram.
HR diagrams for two open clusters, M67 and NGC 188, showing the main sequence turn-off at different ages.. The turnoff point for a star refers to the point on the Hertzsprung–Russell diagram where it leaves the main sequence after its main fuel is exhausted – the main sequence turnoff.
The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars.This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses [citation needed]) late in their lives.
An example of a Hertzsprung–Russell diagram for a set of stars that includes the Sun (center) (see Classification) The time a star spends on the main sequence depends primarily on the amount of fuel it has and the rate at which it fuses it. The Sun is expected to live 10 billion (10 10) years. Massive stars consume their fuel very rapidly and ...
Since color index is the horizontal coordinate in a Hertzsprung–Russell diagram, the different types of star appear in different parts of the CMD despite their common energy source. In effect, the red clump represents one extreme of horizontal-branch morphology: all the stars are at the red end of the horizontal branch, and may be difficult ...
The shape and position of the Hayashi track on the Hertzsprung–Russell diagram depends on the star's mass and chemical composition. For solar-mass stars, the track lies at a temperature of roughly 4000 K. Stars on the track are nearly fully convective and have their opacity dominated by hydrogen ions.