Eta Aquarii

Eta Aquarii, Latinized from η Aquarii, is the Bayer designation for a star in the equatorial constellation of Aquarius. It is visible to the naked eye with an apparent visual magnitude of 4.04. The distance to this star, as determined by parallaxmeasurements, is about 168 light-years (52 parsecs). Eta Aquarii is near the radiant of a meteor shower named after it.

Eta Aquarii has a stellar classification of B9IV-Vn, which may indicate that it is beginning to evolve away from the main sequence into a subgiant as the supply of hydrogen at its core becomes exhausted. It is spinning rapidly with a high projected rotational velocity of 291 km/s. This is causing an equatorial bulge, giving the star an oblate figure with a 24% larger radius at the equator than at the poles. The Doppler effect from the rapid rotation is causing the absorption lines in the star's spectrum to blur, as indicated by the 'n' suffix in the star's classification.