Beta Microscopii, an A-type main-sequence star (a dwarf star that have spectra which are defined by strong hydrogen Balmer absorption lines), with a stellar classification of A2 Vn, is spinning rapidly with a projected rotational velocity of 275 km/s.
This is an A-type main-sequence star with a stellar classification of A2 Vn, where 'n' indicates nebulous absorption lines caused by fast rotation. An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V. These stars have spectra which are defined by strong hydrogen Balmer absorption lines. It is spinning rapidly with a projected rotational velocity of 275 km/s. 
