Meaning of O star

O star

Pronunciation: (ō' stär"), [key]
  1. a very hot, massive, blue star of spectral type O, having a surface temperature between 30,000 and 50,000 K and an absorption spectrum with few lines, though the Balmer series of hydrogen lines is present and lines of ionized helium are detectable.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.