Pollux (Beta Geminorum)


Pollux (Beta Geminorum) is the brightest star in the constellation Gemini (despite its Beta designation), and the 17th brightest in the sky. Pollux is a giant orange K star that makes an interesting color contrast with its white "twin," Castor. Evidence has been found for a a hot, outer, magnetically-supported corona around Pollux, and the star is known to be an X-ray emitter.


visual magnitude 1.16
absolute magnitude 1.08
spectral type K0IIIb
surface temperature 4,500 K
luminosity 32 Lsun
radius 10 Rsun
distance 34 light-years
position R.A. 07h 45m 18.9s,
Dec. +28° 1' 34"


Discovery of a planet around Pollux

On June 16, 2006, a team of astronomers (including A. P. Hatzes, W. D. Cochran, E. Endl, E. W. Guenther, S. H. Saar, G. A. H. Walker, S. Yang, M. Hartmann, M. Esposito, and D. B. Paulson) confirmed the presence of a Jupiter-class planet around Pollux. Pollux b had been first detected in 1993. Assuming a mass for Pollux of 1.7 solar masses, Pollux b has a minimum mass of 2.3 +/– 0.45 Jupiter-masses. It moves around Pollux at an average distance of 1.64 +/– 0.27 AU in a nearly circular orbit (eccentricity = 0.02 +/– 0.03) with a period of 1.6 years (589.64 +/– 0.81 days).