Delta Ceti

Delta Ceti, Latinized from δ Ceti, is a single,[7] blue-white hued star in the equatorial constellation of Cetus. The star's apparent visual magnitude of +4.06[2] means it is near to the cusp of the faintest third of the stars that are visible the ideally-placed naked eye. It is 0.3238° north of the celestial equator compared to the celestial north pole's 90°. It is about 0.74° WNW of the spiral galaxy M77 (but which at apparent magnitude 9.6 needs magnification to be made out and has an apparent size of 0.1° by 0.12°).

Delta Ceti

Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cetus
Right ascension 02h 39m 28.95579s[1]
Declination +00° 19′ 42.6345″[1]
Apparent magnitude (V) +4.06[2]
Characteristics
Spectral type B2 IV[3]
U−B color index −0.88[2]
B−V color index −0.21[2]
Variable type β Cep[3]
Astrometry
Radial velocity (Rv)12.7±0.9[4] km/s
Proper motion (μ) RA: 12.85±0.17[1] mas/yr
Dec.: −2.94±0.11[1] mas/yr
Parallax (π)5.02 ± 0.15[1] mas
Distance650 ± 20 ly
(199 ± 6 pc)
Absolute magnitude (MV)−2.41[5]
Details
Mass8.4±0.7[3] M☉
Radius4.6±0.8[3] R☉
Luminosity4,000[3] L☉
Surface gravity (log g)4.05±0.20[3] cgs
Temperature21,900±1,000[3] K
Metallicity [Fe/H]−0.24[5] dex
Rotational velocity (v sin i)7±4[3] km/s
Age7−18[6] Myr
Other designations
δ Cet, 82 Ceti, BD−00° 406, FK5 91, HD 16582, HIP 12387, HR 779, SAO 110665
Database references
SIMBADdata

Distance and relative motion

Based upon an annual parallax shift of 5.02 mas as seen from Earth,[1] it is around 650 light years from the Sun.

Motion relative to our system's trajectory includes a highly parting vector: with a net radial velocity of about +13 km/s.[4] It moves minutely across the celestial sphere – yet just over four times more in right ascension than in declination.

Inherent properties

This is a Beta Cephei variable[3] with a stellar classification of B2 IV.[3] It varies in brightness with a period of 0.16114 days.[6] The star is about 7−18[6] million years and has a low projected rotational velocity of around 7 km/s,[3] suggesting it is either rotating slowly or is being viewed from nearly pole on.[6] It has 8.4[3] times the mass of the Sun and 4.6[3] times the Sun's radius. The star is radiating around 4,000[3] times the Sun's luminosity from its photosphere at an effective temperature of roughly 21,900 K[3]

Name

This star, along with α Cet (Menkar), λ Cet (Menkar), γ Cet (Kaffaljidhma), μ Cet, ξ1 Cet and ξ2 Cet were Al Kaff al Jidhmah, "the Part of a Hand".[8]

According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Kaff al Jidhmah were 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 (exclude α Cet and λ Cet.)[9]

In Chinese, 天囷 (Tiān Qūn), meaning Circular Celestial Granary, refers to an asterism consisting of δ Ceti, α Ceti, κ1 Ceti, λ Ceti, μ Ceti, ξ1 Ceti, ξ2 Ceti, ν Ceti, γ Ceti, 75 Ceti, 70 Ceti, 63 Ceti and 66 Ceti. Consequently, the Chinese name for δ Ceti itself is 天囷九 (Tiān Qūn jiǔ, English: the Ninth Star of Circular Celestial Granary.)[10]

References
  1. van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.Vizier catalog entry
  2. Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99). Bibcode:1966CoLPL...4...99J.
  3. Hubrig, S.; et al. (January 2009), "New magnetic field measurements of beta Cephei stars and Slowly Pulsating B stars", Astronomische Nachrichten, 330 (4): 317, arXiv:0902.1314, Bibcode:2009AN....330..317H, doi:10.1002/asna.200811187
  4. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
  5. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  6. Neilson, Hilding R.; Ignace, Richard (December 2015), "Period change and stellar evolution of β Cephei stars", Astronomy & Astrophysics, 584: 6, arXiv:1509.05433, Bibcode:2015A&A...584A..58N, doi:10.1051/0004-6361/201526836, A58.
  7. Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x.
  8. Star Name - R.H. Allen p.160
  9. Jack W. Rhoads - Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology; November 15, 1971
  10. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日
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