Tags: Star.
SAO 20575 or BD+60°2522 is a bright O-class star that has produced the Bubble Nebula (NGC 7635) with its stellar wind. The exact classification of the star is uncertain with a number of spectral peculiarities and inconsistencies between the appearance of the star itself and the effects on the nearby nebulosity but it is undoubtedly a highly luminous hot massive star. Direct spectroscopy yields a spectral class of O6.5 and an effective temperature around 37500K.
