Fr.: étoile de type A
A star whose spectrum shows strong hydrogen → Balmer lines accompanied by many faint to moderately strong metallic lines. In contrast to B and O stars, the lines of He I and He II are absent. Their surface temperature ranges from 7,500 to 10,000 K. The main metallic lines seen in A-type stars are those of Fe I and Fe II, Cr I and II, Ti I and II, and account for about two-thirds of all lines. Some famous examples of A star are: → Sirius; → Deneb, → Altair, and → Vega. Also known as A-type star.
A, letter of alphabet used in the → Harvard classification; → type; → star.
post-planetary nebula star
setâre-ye pasâ-miq-e sayyâre-yi
Fr.: étoile post-nébuleuse planétaire
An evolved star whose → planetary nebula has dissipated.