Subdwarf: A subdwarf, sometimes denoted by "sd", is a star with luminosity class VI under the Yerkes spectral classification system. They are defined as stars with luminosity 1.5 to 2 magnitudes lower than that of main-sequence stars of the ... (Star of luminosity class VI under the Yerkes spectral classification system) [100%] 2024-05-22 [Star types] [Subdwarfs]...