Gamma Ceti
Observation data Epoch J2000.0 Equinox J2000.0 |
|
---|---|
Constellation | Cetus |
Right ascension | 02h 43m 18.03910s[1] |
Declination | +03° 14′ 08.9390″[1] |
Apparent magnitude (V) | 3.47[2] (3.56/6.63/10.16)[3] |
Characteristics | |
Spectral type | A3 V + F3 V + K5[3] |
U−B color index | +0.07[2] |
B−V color index | +0.09[2] |
Astrometry | |
Radial velocity (Rv) | –5.1[4] km/s |
Proper motion (μ) | RA: –146.10[1] mas/yr Dec.: –146.12[1] mas/yr |
Parallax (π) | 40.97 ± 0.63[1] mas |
Distance | 80 ± 1 ly (24.4 ± 0.4 pc) |
Details | |
γ Cet A | |
Radius | 1.9[5] R☉ |
Rotational velocity (v sin i) | 186[6] km/s |
Age | 300[7] Myr |
Other designations | |
Gamma Ceti (γ Cet, γ Ceti) is a star system in the equatorial constellation Cetus. It has the traditional name Kaffaljidhma and has an apparent visual magnitude of 3.47.[2] Based upon parallax measurements, this star is located at a distance of about 80 light years (24.4 parsecs) from Earth.[1]
Properties
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.[3] 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 are can be a challenge to resolve even with a much larger scope.[9] 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.[3]
The measured angular diameter of the primary star is 0.74 ± 0.08 mas.[10] At the estimated distance of this system, this yields a physical size of about 1.9 times the radius of the Sun.[5] The secondary component of this system is an X-ray source with a luminosity of 2.2 × 1029 erg s−1.[11] Gamma Ceti is about 300[7] million years old and it appears to be a member of the stream of stars loosely associated with the Ursa Major moving group.[12] The primary has been examined for an excess of infrared emission that would suggest the presence of circumstellar matter, but none was found.[7]
Etymology
The title Kaffaljidhma was derived from Arabic الكف الجذماء Al Kaff al Jidhmah, meaning "The cut-short hand".[13] 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 Kaffaljidhma, 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).[14]
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.)[15]
References
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- ↑ 5.0 5.1 Lua error in package.lua at line 80: module 'strict' not found.. The radius (R*) is given by:
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- ↑ 7.0 7.1 7.2 Lua error in package.lua at line 80: module 'strict' not found.
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- ↑ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日
External links
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