NGS Style Manual‎ > ‎- S -‎ > ‎

STAR NAMES

Capitalize officially recognized names for stars; write out and capitalize a Greek letter used to designate a star:
            Alpha Centauri
            Betelgeuse, Alpha Orionis
    
        Polaris, the North Star
            Gliese 436
            55 Cancri
            Mu Arae
but     Barnard’s star

See also Astronomical Terms.