An A star is a star of spectral type
A, white in color, with a spectrum dominated by the Balmer
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 times that of the Sun, and masses of 1.5 to 3 solar masses. Familiar
examples include Sirius
A-type supergiants, such as Deneb,
may be as hot as 11,000 K and have masses up to 16 solar masses and luminosities
of up to 35,000 times that of the Sun.
Among A-type peculiar stars are Ae
stars, Am stars (which have strong and often variable absorption lines of certains metals and deficiences of others), 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.