A0V

A0V is a stellar classification used in the Morgan–Keenan (MK) spectral system to denote hot, blue-white main-sequence stars. The spectral type A0 sits at the hotter end of the A class, and the luminosity class V indicates that the star is a main-sequence dwarf, fusing hydrogen in its core. A0V stars are among the more luminous stars on the main sequence.

Typical physical properties of A0V stars include an effective temperature around 9,500 to 10,000 K, a mass of roughly 2 to 3 solar masses, and a radius near 2 solar radii. They shine with tens of solar luminosities, often in the range of about 25 to 100 Ls. Their spectra feature prominent hydrogen Balmer lines and relatively fewer metal lines compared with cooler stars. Many A0V stars rotate rapidly, which broadens spectral lines and can influence the shape of the star’s observed spectrum.

Vega (Alpha Lyrae) is the best-known prototype of the A0V class and is frequently used as a photometric standard. Some A0V stars also exhibit infrared excess due to circumstellar debris disks, reflecting ongoing or remnant planetary system activity in certain cases. Because they are bright and well-studied, A0V stars serve as calibration anchors in various observational programs and as reference points for comparing other A-type stars.

In stellar evolution, A0V stars spend a finite but substantial period on the main sequence, typically up to around a billion years or more depending on mass, before evolving into later evolutionary stages.