A-type main-sequence star
A-type main-sequence stars are hot, bright stars that fuse hydrogen in their cores. They have spectral type A and are on the main sequence, meaning they are still burning hydrogen.
Typical properties: mass about 1.7–2.2 times the Sun; surface temperatures about 7,600–10,000 kelvin; luminosities roughly 8–38 times that of the Sun. They show strong hydrogen lines in their spectra.
Life span: they live much shorter than the Sun, roughly a quarter as long.
Why they’re interesting: many A-type stars have debris disks where planets form. They rotate quickly, which makes it harder to detect planets with the usual Doppler method, but planets have been found or directly imaged around some A-type stars, such as Beta Pictoris and HR 8799; there is also a well-known hot Jupiter around HD 15082 (WASP-33). As these stars age and become cooler red giants, planets can be found more easily with radial-velocity methods.
Nearby bright examples include Vega, Sirius A, and Altair.
This page was last edited on 2 February 2026, at 21:50 (CET).