About HD 163181
HD 163181 is an epic variable star. It sits in the constellation Sco, shines at apparent magnitude 6.59 and has spectral type O9.5Ia/ab.
Its spectrum reads O9.5Ia/ab — an O-type star — the hottest, rarest main class there is. Fewer than one star in a million is an O, and none of them lasts long.