Gamma Ceti

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Gamma Ceti
Diagram showing star positions and boundaries of the Cetus constellation and its surroundings
Cercle rouge 100%.svg

Location of γ Ceti (circled) near the center
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
Gam Cet, 86 Ceti, BD+02 422, HD 16970, HIP 12706, HR 804, SAO 110707.[8]

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

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ 2.0 2.1 2.2 2.3 Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ 3.0 3.1 3.2 3.3 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ 5.0 5.1 Lua error in package.lua at line 80: module 'strict' not found.. The radius (R*) is given by:
    \begin{align} 2\cdot R_* & = \frac{(24.4\cdot 0.74\cdot 10^{-3})\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\ & \approx 3.88\cdot R_{\bigodot} \end{align}
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ 7.0 7.1 7.2 Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日

External links

  • Lua error in package.lua at line 80: module 'strict' not found.
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