Achernar

Marking the southern end of the river constellation Eridanus, Achernar sits at a declination of −57° and never rises for most northern observers. It is Alpha Eridani, a blue-white B-type star whose hot colour is reflected in a negative B–V index of −0.158. At apparent magnitude 0.45 it is one of the brightest stars of the far southern sky, and its absolute magnitude of −2.7 confirms an intrinsic luminosity well above the Sun's. The star lies about 139 light-years away. Its combination of southern isolation and blue-white brilliance makes Achernar a defining marker for navigators and observers of the southern celestial hemisphere.