Delta Geminorum
 Location of δ Geminorum (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Gemini |
| Right ascension | 07h 20m 07.37978s |
| Declination | +21° 58′ 56.3377″ |
| Apparent magnitude (V) | +3.53 |
| Characteristics | |
| Spectral type | F0 IV |
| U−B color index | +0.04 |
| B−V color index | +0.34 |
| Astrometry | |
| Radial velocity (Rv) | +4.1 km/s |
| Proper motion (μ) |
RA: –15.13 mas/yr Dec.: –9.79 mas/yr |
| Parallax (π) | 53.94 ± 0.66mas |
| Distance | 60.5 ± 0.7 ly (18.5 ± 0.2 pc) |
| Absolute magnitude (MV) | 1.95 |
| Details | |
| Mass | 1.57 M☉ |
| Temperature | 6,900 K |
| Metallicity [Fe/H] | –0.26 dex |
| Rotational velocity (v sin i) | 129.7 km/s |
| Age | 1.6 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Delta Geminorum (δ Geminorum, abbreviated Delta Gem, δ Gem), also named Wasat, is a triple star system in the constellation of Gemini.
δ Geminorum (Latinised to Delta Geminorum) is the system's Bayer designation.
It bore the traditional name Wasat, which derives from the Arabic word for "middle". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Wasat for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
In Chinese, 天樽 (Tiān Zūn), meaning Celestial Wine Cup, refers to an asterism consisting of Delta Geminorum, 57 Geminorum and Omega Geminorum. Consequently, Delta Geminorum itself is known as 天樽二 (Tiān Zūn èr, English: the Second Star of Celestial Wine Cup.). From this Chinese name, the name Ta Tsun has appeared.
Delta Geminorum is a subgiant star with the stellar classification F0 IV. It is about 60.5 light-years (18.5 parsecs) distant. This star has 1.57 times the mass of the Sun and is rotating rapidly with a projected rotational velocity of 129.7 km s−1. The estimated age is 1.6 billion years.
It has an apparent visual magnitude of +3.53, allowing it to be seen with the naked eye. It is only two-tenths of a degree south of the ecliptic, and therefore is occasionally occulted by the Moon and, more rarely, by a planet. The last occultation by a planet was by Saturn on June 30, 1857, and the next will be by Venus on August 12, 2420. In 1930, the dwarf planet Pluto was discovered about 0.5° to the east of this star by American astronomer Clyde Tombaugh.
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