Abstract
The author discusses the spectral morphology of luminous hot stars in the Small Magellanic Cloud and how the low metallicity of this galaxy has impacted upon the accuracy of their classification. He demonstrates conclusively that the neglect of the three-dimensional nature of spectral classification, as represented by temperature, luminosity, and metallicity, has resulted in considerable uncertainty in the optical classification of B-type and A-type supergiants. It is shown that the startling differences which exist between the UV spectra of O-stars in the SMC and in the LMC/Galaxy also exist for the most luminous B-type supergiants. The authors demonstrates that this uncertainty in spectral classification for the SMC supergiants may be an important factor influencing previous investigations of the use of blue supergiants as distance indicators.
