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A blue horizontal branch star (BHB) is a star at the bluer (hotter) end of the horizontal branch. In general, blue stars suggest young, early stars and recent star formation, but the stars labeled blue horizontal branch are blue stars found in globular clusters unlikely to have such recent star formation. They show hydrogen spectral lines, a Balmer jump, and not many lines that would indicate metallicity, and are interpreted as horizontal-branch low-metallicity stars. They range from 0.5-1 solar masses, with a similarly-limited luminosity range, giving them the potential for use as standard candles.