B starsStars of spectral type B that are massive hot blue stars with a surface temperature (T eff) of about 10 000 to 28 000 kelvin for main-sequence stars, and up to 30 000 kelvin for supergiants. Absorption lines of neutral helium (He I) dominate the spectrum, reaching maximum intensity for B2 stars. Balmer lines of hydrogen strengthen from B0 to B9; lines of ionized magnesium and silicon are also present. A few B stars – the Be stars – also have emission lines from a circumstellar shell of gas. B0, B1, and B2 stars are found in OB associations in the spiral arms of galaxies. Spica, Rigel, Bellatrix, and Alpha Crucis are B stars.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006