Castor is a complex sextuple system of hot, bluish-white type A stars and dim red dwarfs, while Pollux is a single, cooler yellow-orange giant.

In July 2014 the International Astronomical Union launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars.

[25] In Chinese, 北河 (Běi Hé), meaning North River, refers to an asterism consisting of Pollux, ρ Geminorum, and Castor.

[26] Consequently, Pollux itself is known as 北河三 (Běi Hé sān, English: the Third Star of North River.

)[27] At an apparent visual magnitude of 1.14,[28] Pollux is the brightest star in its constellation, even brighter than its neighbor Castor (α Geminorum).

[29] Parallax measurements by the Hipparcos astrometry satellite[30][31] place Pollux at a distance of about 33.78 light-years (10.36 parsecs) from the Sun.

[37] Evidence for a low level of magnetic activity came from the detection of weak X-ray emission using the ROSAT orbiting telescope.

[33] The star displays small amplitude radial velocity variations, but is not photometrically variable.

[11] The existence of Pollux b has been disputed; the possibility that the observed radial velocity variations are caused by stellar magnetic activity cannot be ruled out.