The Be star Achernar, flattened by extremely rapid rotation (*)
Achernar (α Eri / α Eridani / Alpha Eridani), sometimes spelled Achenar, is the brightest star in the constellation Eridanus and the eighth-brightest star in the nighttime sky. It lies at the southern tip of the constellation.
Achernar is a bright, blue B-type star of six to eight solar masses lying approximately 144 light years away. Although classified as a main-sequence (dwarf) star, it is about 3,000 times more luminous than the Sun. Achernar is in the deep southern sky and never rises above 33°N. Achernar is best seen from the southern hemisphere in November; it is circumpolar below 33°S.
Until about March 2000, Achernar and Fomalhaut were the two first-magnitude stars furthest in angular distance from any other first-magnitude star in the celestial sphere. Antares, in the constellation of Scorpius, is now the most isolated first-magnitude star.
It is the least spherical star in the Milky Way studied to date. Achernar spins so rapidly that its equatorial diameter is more than 50% greater than its polar diameter.
The name comes from the Arabic آخر النهر ākhir an-nahr "river's end".
It is known as 水委一 (Shuǐwěiyī, the First Star of the Crooked Running Water) in Chinese.