Kappa Geminorum

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.

κ Geminorum

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.

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]