PyXPlot

Examples - HR Diagram

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A Hertzsprung Russell Diagram

Script

set nokey
set size square
set xlabel '$B-V$ colour'
set ylabel 'Absolute magnitude $M$'
plot [-0.4:2][14:-4] 'hrdiagram.dat.gz' w d ps 3
      

Notes

Hertzsprung-Russell (HR) Diagrams are scatter-plots of the luminosities of stars plotted against their colours which reveal that most normal stars lie along a tight line called the main sequence, whilst unusual classes of stars -- giants and dwarfs -- can be readily identified on account of their not lying along this main sequence. The principal difficulty in constructing accurate HR diagrams is that the luminosities L of stars can only be calculated from their observed brightnesses F, using the relation L=Fd^2 if their distances d are known. In this example, we construct an HR diagram using observations made by the European Space Agency's { t Hipparcos} spacecraft, which accurately measured the distances of over a million stars between 1989 and 1993.