Pollux or Beta Geminorum (Bet Gem) is the brightest naked eye star in the constellation Gemini. With an apparent magnitude of 1.16, Pollux is the 17th brightest star in the entire sky (see: 50 Brightest Stars ). Its absolute magnitude is 1.09 and its distance is 33.7 light years. The Equinox J2000 equatorial coordinates are RA = 07h 45m 18.9s, Dec = +28° 01' 34".

Pollux has a spectral type of K0III, a surface temperature of 4865° Kelvin and a luminosity 32 times the Sun. It has a mass of 1.86 solar masses and a diameter 8 times the Sun.

The image above shows the uncropped view of Pollux (North is up) through the Takahashi E-180 Astrograph.

The Gemini "twin" stars Castor and Pollux are best seen during northern spring evenings. Unlike real twins, Castor and Pollux have very little in common. Castor is a white quadruple star with fairly close hot white (spectral class A) components while Pollux an orange-colored cool (spectral type K0IIIb) giant. The close pairing with Castor makies Pollux's color more vivid. At a distance of 34 light years, the total luminosity is 46 times that of the Sun. With its cool temperature (4770° Kelvin) and a diameter 10 times the Sun's, Pollux is smaller than most of its cool giant "cousins" and only a quarter the diameter of Aldebaran. As is a typical of many red giants, it is quietly fusing helium into carbon and oxygen in its deep core. It emits X-rays and seems to have a hot, outer, magnetically supported corona similar to that surrounding our Sun.

In 2006, Pollux was confirmed to have an extrasolar planet orbiting it, making it the brightest star in the sky with a known planet. With a mass at least 2.9 times that of Jupiter, the planet orbits in a nearly circular path at a average distance of 1.69 Astronomical Units with a period of 590 days (1.6 years). Like many other planet-holding stars, Pollux is metal-rich, with an iron content (relative to hydrogen) 55 percent higher than solar. From the planet, which is bathed with a radiation intensity 16 times the amount we get from the Sun, Pollux would glower in the sky with an angular diameter of nearly 3 degrees, 5.7 times bigger than we see the Sun.

The description above is based on the Pollux entry in Stars (Jim Kaler). For more information about Pollux, see Wikipedia.

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