Kappa Geminorum
Binary star system in the constellation Gemini
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Kappa Geminorum (κ Geminorum, κ Gem) is a binary star system in the northern zodiac constellation of Gemini. It is visible to the naked eye with an apparent visual magnitude of 3.568.[2] Based upon an annual parallax shift of 23.07 mas,[1] the system is located about 141 light years distant from the Sun.
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Gemini |
| Right ascension | 07h 44m 26.85357s[1] |
| Declination | +24° 23′ 52.7872″[1] |
| Apparent magnitude (V) | 3.568[2] + 8.2[3] |
| Characteristics | |
| Spectral type | G9 III[4] |
| U−B color index | +0.700[2] |
| B−V color index | +0.941[2] |
| Astrometry | |
| Radial velocity (Rv) | 20.6[5] km/s |
| Proper motion (μ) | RA: −23.39[1] mas/yr Dec.: −54.57[1] mas/yr |
| Parallax (π) | 23.07±0.22 mas[1] |
| Distance | 141 ± 1 ly (43.3 ± 0.4 pc) |
| Absolute magnitude (MV) | +0.35[6] |
| Details | |
| Mass | 2.07[7] M☉ |
| Radius | 11.00±0.16[8] R☉ |
| Luminosity | 69.3±3.7[8] L☉ |
| Surface gravity (log g) | 2.8[9] cgs |
| Temperature | 5,020±68[8] K |
| Metallicity [Fe/H] | −0.16[9] dex |
| Rotational velocity (v sin i) | 3.3[9] km/s |
| Age | 2.07[7] Gyr |
| Other designations | |
| κ Gem, 77 Geminorum, BD+24°1759, FK5 294, HD 62345, HIP 37740, HR 2985, SAO 79653.[10] | |
| Database references | |
| SIMBAD | data |
In Chinese astronomy, Kappa Geminorum is called 積薪, Pinyin: Jīxīn, meaning Pile of Firewood, because this star is marking itself and stand alone in Pile of Firewood asterism, Well mansion (see : Chinese constellation).[11] 積薪 (Jīxīn) westernized into Tseih Tsing, but the name Tseih Tsing was designated for χ Gem and μ Cnc by R.H. Allen, with the meaning is "piled-up fuel"[12] In Japanese, 隆博星 (Takahiro-boshi), meaning "Esteemed Nobility Star," refers to the Japanese description of κ Geminorum.[citation needed]
This is a probable astrometric binary[3] system with the components having an angular separation of 7.2 arcseconds along a position angle of 241°, as of 2014.[13] The primary is an evolved G-type giant star with a stellar classification of G9 III.[4] Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[14] It has double the mass of the Sun,[7] but has expanded to 11 times the solar radius. The star radiates around 69 times the Sun's luminosity from its outer atmosphere at an effective temperature of 5,020 K.[8] It shows a leisurely spin with a projected rotational velocity of 3.3 km/s, and is around two billion years old.[7] The secondary component is a magnitude 8.2 star.[3]