Pollux (Beta Geminorum)
Coordinates, Hipparcos parallax (96.54 mas, 33.78 ly), magnitude 1.14, exoplanet Pollux b (Thestias), and observing guide for Pollux in Gemini.
Provenance-Backed Scientific Measurements
Every measurement below preserves its unit, uncertainty interval, observational method, reference epoch, quality status, and primary catalog source. See Uncertainty & Provenance for how competing measurements are handled.
| Parameter | Value | Uncertainty | Method & Epoch | Quality Status | Source Archive |
|---|---|---|---|---|---|
| Apparent visual magnitude (V) | 1.14 mag | ± 0.01 mag | Johnson UBV photoelectric standard star | definitive | Hipparcos New Reduction Catalog |
| Trigonometric parallax | 96.54 mas | ± 0.27 mas | Hipparcos New Reduction astrometric solution (10.358 ± 0.029 pc) (J2000.0) | definitive | Hipparcos New Reduction Catalog |
| Distance in light-years | 33.78 ly | ± 0.09 ly | Derived from Hipparcos parallax 96.54 ± 0.27 mas | definitive | Hipparcos New Reduction Catalog |
| Linear photospheric radius | 9.06 R☉ | ± 0.03 R☉ | CHARA/Mark III limb-darkened angular diameter (7.980 ± 0.020 mas) at 10.36 pc | definitive | SIMBAD Astronomical Database (CDS) |
| Stellar mass (asteroseismic + interferometric) | 1.91 M☉ | ± 0.09 M☉ | MOST space asteroseismology & interferometric radius (Hatzes et al. 2012) | high-confidence | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Pollux (Beta Geminorum Planet-Hosting Giant) at RA 07h 45m 18.95s, Dec +28° 01′ 34.3″ within Gemini, alongside peak meridian transit altitudes for 40°N and 30°S observers. Use the RA/Dec Coordinate Converter to compute exact culmination altitude for your latitude.
Astrophysical Context & Structure
Pollux (Beta Geminorum) is the brightest star in the zodiacal constellation Gemini (outshining Alpha Geminorum, Castor, at magnitude 1.14 vs 1.58) and the seventeenth-brightest star in the night sky. Located just 10.358 ± 0.029 parsecs (33.78 light-years) from Earth, Pollux is the closest giant star of any kind to our Solar System—even closer than Arcturus (36.7 ly).
With a mass of 1.91 solar masses, a radius of 9.06 solar radii, and an effective surface temperature of 4,865 K, Pollux is an evolved K0 III 'red clump' giant that has already settled into stable core helium fusion and radiates 32.7 times the bolometric luminosity of the Sun. Spectropolarimetry with the NARVAL instrument at Pic du Midi also detected a weak sub-Gauss surface magnetic field generated by convective dynamo action in its deep envelope.
In 2006 Artie Hatzes and colleagues confirmed a long-suspected 589.64-day (1.61-year) radial-velocity oscillation first noticed in 1993, proving that Pollux is orbited at a semi-major axis of 1.64 AU by a massive gas-giant exoplanet, Pollux b (officially named Thestias by the IAU), with a minimum mass of 2.30 Jupiter masses—making Pollux the brightest star in Earth's sky known to host a confirmed planetary system.
Practical Visual Observing Guide
- Situated 4.5° southeast of Castor at the heads of the Gemini Twins, Pollux displays a warm golden-apricot tint that contrasts immediately with snowy-white Castor A and B.
- Because Pollux is a K0 III standard star of the Morgan–Keenan spectral classification system, it serves as the benchmark visual reference for 4,865 K orange-yellow giant star coloration.
Catalog Cross-Identifications & Aliases
Common Aliases: β Geminorum · HD 62509 · HIP 37826 · 78 Geminorum
| Catalog Authority | Identifier |
|---|---|
| HIP | HIP 37826 |
| HD | HD 62509 |
| SIMBAD | * bet Gem |
| WIKIDATA | Q13028 |
Related Objects, Comparisons & Guides
Castor (Alpha Geminorum Sextuple System)
Coordinates, Hipparcos distance (50.8 ly), 5.6″ A–B binary orbit, YY Geminorum eclipsing pair, and observing guide for Castor.
Arcturus (Alpha Bootis Red Giant)
Coordinates, Hipparcos distance (36.7 ly), magnitude −0.05, halo-stream kinematics, and observing guide for Arcturus in Boötes.
Aldebaran (Alpha Tauri Orange Giant)
Coordinates, Hipparcos distance (66.6 ly), 45.1 R☉ radius, Hyades foreground alignment, and observing guide for Aldebaran in Taurus.
Stellar Spectral Classification (OBAFGKM)
Reference guide to Morgan-Keenan (MK) stellar classification (O B A F G K M), luminosity classes (I–V, WD), color index (B-V), and the H-R diagram.
Exoplanet Transit & Radial Velocity Methods
How astronomers detect and characterize exoplanets using photometric transit depth ((Rp/R*)²), Doppler radial velocity (M sin i), and JWST transmission spectra.
Scientific Sources & Dataset Provenance
- Hipparcos New Reduction Catalog (2007 New Reduction): van Leeuwen, F. 2007, A&A, 474, 653 (Validation of the new Hipparcos reduction) — ESA / van Leeuwen (2007)
- NASA Exoplanet Archive (2026-10-01 snapshot): Akeson, R. L., et al. 2013, PASP, 125, 989; NASA Exoplanet Archive (IPAC/Caltech) — NASA Exoplanet Science Institute (NExScI / Caltech / IPAC)
- SIMBAD Astronomical Database (CDS) (2026-10 release): Wenger, M., et al. 2000, A&AS, 143, 9 (The SIMBAD astronomical database) — Centre de Données astronomiques de Strasbourg