Proper noun
(astronomy) A bluish-white star in the constellation Grus; Alpha (α) Gruis.
(astronomy) A bluish-white binary star in the constellation Centaurus; Zeta (ζ) Centauri.
Source: en.wiktionary.orgIt is a variable star with a minimum magnitude of 2.3 and a maximum magnitude of 2.0. citation An imaginary line drawn from the Great Square of Pegasus through Fomalhaut will lead to Alnair and Beta Gruis. Source: Internet