Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Eta Centauri is a star in the constellation Centaurus. It is a rapidly rotating star that completes a full rotation in less than a day. It is also a Be star, which means it has variable emissions in its hydrogen spectral lines. Finally it is also slightly variable, and classified as a Gamma Cassiopeiae variable, with multiple periods of variability. It is approximately 309 light years from Earth. Eta Centauri is sufficiently large that it is on the dividing line between stars that evolve into white dwarfs and those that turn into supernovae.