Worlds of David Darling
Encyclopedia of Science
Home > Encyclopedia of Science

A star

A-type star spectrm
An A star is a star of spectral type A, white in color, with a spectrum dominated by the Balmer series of hydrogen. Lines of heavy elements, such as iron, are noticeable at the cooler end of the range. Main sequence A stars have surface temperatures of 7,500 to 9,900 K, luminosities of 7 to 80 Lsun, and masses of 1.5 to 3 Msun. Familiar examples include Sirius, Vega, and Altair.

A-type supergiants, such as Deneb, may be as hot as 11,000 K and have masses up to 16 Msun and luminosities of up to 35,000 Lsun.

Among A-type peculiar stars are Ae stars, Am stars, and Ap stars. Also, two of the main kinds of pulsating variables, RR Lyrae stars and Delta Scuti stars, have surface temperatures in the A-star range.

Related category