Pollux (star)
From Wikipedia, the free encyclopedia
 The position of Pollux within the constellation of Gemini. |
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| Observation data Epoch J2000.0 Equinox J2000.0 |
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|---|---|
| Constellation | Gemini |
| Right ascension | 07h 45m 19.4s |
| Declination | +28° 01′ 35″ |
| Apparent magnitude (V) | 1.15 |
| Characteristics | |
| Spectral type | K0IIIb |
| U-B color index | 0.86 |
| B-V color index | 1.00 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | +3.3 km/s |
| Proper motion (μ) | RA: −625.69 mas/yr Dec.: −45.95 mas/yr |
| Parallax (π) | 96.74 ± 0.87 mas |
| Distance | 33.7 ± 0.3 ly (10.34 ± 0.09 pc) |
| Absolute magnitude (MV) | 1.09 |
| Details | |
| Mass | 1.86 M☉ |
| Radius | 8.0 R☉ |
| Luminosity | 32 L☉ |
| Temperature | 4,865 K |
| Metallicity | 90% Sun |
| Rotation | 38 days |
| Other designations | |
| Database references | |
| SIMBAD | data |
| ARICNS | data |
Pollux, also catalogued as Beta Geminorum (β Gem / β Geminorum), is an orange giant star approximately 34 light-years from Earth in the constellation of Gemini (the Twins). Pollux is the brightest star in the constellation, brighter than Castor (Alpha Geminorum). As of 2006[update], Pollux was confirmed to have an extrasolar planet orbiting it.
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[edit] Naming
The name Pollux refers specifically to Castor and Pollux, the sons of Leda.[1] The star also bears Arabic name Al-Ras al-Tau'am al-Mu'akhar,(الرأس التؤام المؤخر), literally, 'The Head of the Second Twin.' Historically, the Chinese recognized Pollux as Yang, which in ancient philosophy was one of the two fundamental principles upon which all things depend. Castor and Pollux together correspond to the Nakshatra Punarvasu in Hindu astronomy.
Castor and Pollux are the two 'heavenly twin' stars giving the constellation Gemini (Latin, 'the twins') its name. The stars, however, are nothing alike. Castor is a complex sextuple system comprised of hot, bluish-white A-type stars and dim red dwarfs, while Pollux is a single, cooler yellow-orange giant. The name is traditionally thought by some people[who?] to carry the meaning 'much wine,' since astrologers associate Pollux with prosperity and celebration with wine.
[edit] Stellar components
Pollux is an orange giant star of the spectral type of "K0IIIb". It has been calculated that the star has about 1.7 time more mass than the Sun, 8.8 times more radius, and 32 times more luminosity. Beginning around 1990, Pollux has been measured to be around 85 to 155 percent as enriched with elements heavier than hydrogen (based on its abundance of iron).[clarification needed]
Because Pollux is more massive and more evolved than the Sun, it is thought that the star is likely to be much older than the Sun. Pollux's high mass estimates suggest that it has not yet suffered substantial mass loss. It would then evolve to the first ascent of the red giant branch.
[edit] Planetary system
Announced on June 16, 2006, the confirmation of the suspected extrasolar planet Pollux b or 'Polydeuces' was finally detected. Assuming that Pollux has more mass than the Sun, Pollux b has been calculated to have a minimum mass of 2.3 times that of Jupiter. The planet orbits Pollux at an average distance of 1.64 astronomical units in an almost circular orbit that takes approximately 590 days to complete. Pollux b is currently one of the few planets to be orbiting a star that is visible to the naked eye. The planet is located in an equivalent position of between Earth and Mars in our solar system but with its giant orange sun bathing it in 16 times the solar radiation and looming six times larger in its skies, this superjovian world and any of its moons are – beyond much reasonable doubt - currently uninhabitable. Given the star began life as a fairly sun-like main-sequence star which was probably only slightly more massive and brighter than our Sun it is concievable that life could possibly have existed on a hypothetical large moon of 'Polydeuces' before Pollux ballooned into its current giant state. The planet is also the only confirmed planet to secure the traditional name of its parent star. It is sometimes unofficially called "Polydeuces" based on an alternative version of Pollux’s name. (Source : "The Unearthly Twin - planet of an orange giant" by S. Raine in 'Sky & Space' magazine, Sept-Oct. 2007.)
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity |
|---|---|---|---|---|
| b | 2.3 ± 0.45 MJ | 1.64 ± 0.27 | 589.64 ± 0.81 | 0.02 ± 0.03 |
[edit] References
- ^ "Pollux". STARS. University of Illinois, Urbana-Champaign Campus. 2008. http://www.astro.illinois.edu/~jkaler/sow/pollux.html. Retrieved 2009-05-29.
[edit] See also
[edit] External links
- Hatzes et al. (2006-06-16). "Confirmation of the Planet Hypothesis of the Long-period Radial velocity Variations of β Geminorum". European Southern Observatory. http://exoplanet.eu/papers/bgempaper.pdf. Retrieved 2008-06-24.
- "Notes for star HD 62509". The Extrasolar Planets Encyclopaedia. http://exoplanet.eu/star.php?st=HD+62509. Retrieved 2008-06-24.
- "Pollux". SolStation. http://www.solstation.com/stars2/pollux.htm. Retrieved 2005-11-21.
- "Precise Radial Velocities of Giant Stars II. Pollux and its Planetary Companion". arXiv. 2006-07-07. http://arxiv.org/abs/astro-ph/0607136. Retrieved 2008-06-24.
Coordinates: 
07h 45m 19.4s, +28° 01′ 35″
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