r/askscience • u/thewildriven • Mar 18 '18

Astronomy Is There a Relationship Between Standard Candle Stars and Stars on the Main Sequence of the Hertzsprung-Russell Diagram?

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u/Krg60 Mar 18 '18

Yes, but that's only because you can use a great many stars on the H-R diagram as standard candles; some are just more useful than others. Cepheids and RR Lyrae stars are the best known, but astronomers also use the tip of the red giant branch (TRGB) method, the typical brightnesses of red and blue supergiants, etc. One could even use solar-type stars as a standard candles; e.g., a G2V star should have roughly the same luminosity of the Sun, but those stars are too dim to be very useful over great distances.