Epoch J2000.0 Equinox J2000.0
|Right ascension||02h 43m 18.03910s|
|Declination||+03° 14′ 08.9390″|
|Apparent magnitude (V)||3.47 (3.56/6.63/10.16)|
|Spectral type||A3 V + F3 V + K5|
|U−B color index||+0.07|
|B−V color index||+0.09|
|Radial velocity (Rv)||–5.1 km/s|
|Proper motion (μ)||RA: –146.10 mas/yr
Dec.: –146.12 mas/yr
|Parallax (π)||40.97 ± 0.63 mas|
|Distance||80 ± 1 ly
(24.4 ± 0.4 pc)
|γ Cet A|
|Surface gravity (log g)||3.96 cgs|
|Metallicity [Fe/H]||0.00 dex|
|Rotational velocity (v sin i)||186 km/s|
Gamma Ceti (γ Cet, γ Ceti), also named Kaffaljidhma,is a star system in the equatorial constellation Cetus. It has an apparent visual magnitude of 3.47. Based upon parallax measurements, this star is located at a distance of about 80 light years (24.4 parsecs) from Earth.
γ Ceti has been called Al Kaff al Jidhmah, or Kaffaljidhma, derived from Arabic الكف الجذماء meaning "The cut-short hand". According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Kaff al Jidhmah was originally the title for five stars: γ Cet as Kafaljidma, ξ1 Cet as Al Kaff al Jidhmah I, ξ2 Cet as Al Kaff al Jidhmah II, δ Cet as Al Kaff al Jidhmah III and μ Cet as Al Kaff al Jidhmah IV (excluding α Cet and λ Cet). 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 Kaffaljidhma for Gamma Ceti A on February 1st, 2017 and it is now so entered in the IAU Catalog of Star Names.
In Chinese, 天囷 (Tiān Qūn), meaning Circular Celestial Granary, refers to an asterism consisting of γ Ceti, α Ceti, κ1 Ceti, λ Ceti, μ Ceti, ξ1 Ceti, ξ2 Ceti, ν Ceti, δ Ceti, 75 Ceti, 70 Ceti, 63 Ceti and 66 Ceti. Consequently, γ Ceti itself is known as 天囷八 (Tiān Qūn bā, English: the Eighth Star of Circular Celestial Granary.)
Gamma Ceti appears to be a triple star system. The inner pair have an angular separation of 2.6 arcseconds. The primary component of this pair is a visual magnitude 3.6, A-type main sequence star with a stellar classification of A3 V. The fainter secondary component is an F-type main sequence star that has a classification of F3 V and a magnitude of 6.6. The contrasting colors of these two stars makes them a popular target of amateur astronomers. The two can be resolved with a small, 4 in (10 cm) aperture telescope under ideal seeing conditions, although at times they can be a challenge to resolve even with a much larger scope. At a wide separation of 840 arcseconds is a dim, magnitude 10.2 K-type star with a classification of K5. The luminosity class of this last component remains undetermined.
The measured angular diameter of the primary star is 0.74 ± 0.08 mas. At the estimated distance of this system, this yields a physical size of about 1.9 times the radius of the Sun. The secondary component of this system is an X-ray source with a luminosity of 2.2 × 1029 erg s−1. Gamma Ceti is about 300 million years old and it appears to be a member of the stream of stars loosely associated with the Ursa Major moving group. The primary has been examined for an excess of infrared emission that would suggest the presence of circumstellar matter, but none was found.
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