Pollux

Pollux is Beta Geminorum, apparent magnitude 1.14, at roughly 34 light years, the brightest star in Gemini and the nearest bright giant to the Sun. It is an orange giant of type K0, and it hosts a confirmed planet, a gas giant several times the mass of Jupiter, detected by the wobble it induces and formally named Pollux b, one of the first exoplanets found around a bright, easily seen star. Pollux and Castor together mark the heads of the two twins.

Pollux b, confirmed in 2006, orbits at roughly 1.6 astronomical units, well within what would be the frost line of a Sun-like star but here scorched by Pollux's much greater luminosity as an evolved giant; it was among the first planets found around a star bright enough to be a familiar naked-eye object rather than a faint telescopic target, which made it something of a landmark discovery for public interest in exoplanets. Pollux's confirmed planet has renewed astronomical interest in a star that medieval and Renaissance observers knew only as a bright naked-eye point, a reminder that even the most historically storied stars can still yield new discoveries under modern instruments. Its designation as Beta rather than Alpha, despite outshining Castor, is one of the more frequently noted exceptions to Bayer's rough brightness-ordering convention.

Sources AstronomyAndrew Fraknoi, David Morrison, and Sidney C. Wolff (OpenStax) with Almagest (Mathematike Syntaxis)Claudius Ptolemy

Ptolemy gives Pollux the nature of Mars, and the tradition reads it for a spirited, bold and sometimes rash character, contentiousness, and courage under adversity, with Robson adding the usual freight of danger and violence that later writers heaped on the martial stars. The contrast with Castor is the point: the ancient reading assigns the mortal twin the gentle Mercury and the immortal twin the fierce Mars, so that the pair encodes a division of temperament as well as of fate. Pollux is the more dependable of the two to cite, since Ptolemy names it and the attribution has been stable ever since.

The Castor-Pollux division of Mercury and Mars along the line of mortal and immortal twin is neat enough that it is sometimes assumed to be a later systematiser's tidy invention, but the assignment already appears in Ptolemy, which places the pairing squarely within the earliest surviving layer of fixed-star doctrine rather than among the later medieval or Renaissance elaborations that fill out so much of the rest of the catalogue. The martial reading given to the immortal twin sits oddly against Pollux's mild, Sun-like orange-giant nature astronomically, a case where the mythological logic of the pairing, not any observed property of the star, entirely drives the delineation.