This page illustrates the spectrum of a helium-rich O "subdwarf" star, an extremely hot star which is in the process of evolving into a white dwarf. The near equality of the strengths of the H + He II blends with the He II lines indicates that the atmosphere (and probably the whole of this star) are almost pure helium, with very little if any hydrogen. This star is the exposed core of a star that has thrown off its outer envelope.
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