Herbig Ae/Be star

A Herbig Ae/Be star is a still-contracting (pre-main sequence) star of spectral type A or B, with strong emission lines (especially H-alpha and the calcium H and K lines), associated with fairly bright nebulosity; named after the American astronomer George Herbig (1920–2013) and also known as a Herbig-Bell star or a Herbig emission star. A well-known example is R Coronae Borealis (see R Coronae Borealis star. The number of Herbig Ae/Be stars is smaller than the number of T Tauri stars (lower mass pre-main-sequence stars), for two reasons: higher mass stars in general are less common, and also the timescale for the core contraction of Ae/Be stars is smaller than for stars of smaller mass, so they remain deeply embedded until the end of their mass accretion stage.