Kappa Tauri

Kappa Tauri (κ Tau, κ Tauri) is a double star in the constellation Taurus, the two components κ1 Tauri and κ2 Tauri both members of the Hyades open cluster. The pair are approximately 150 light years from Earth and are separated from each other by about six light years.

Kappa Tauri
Observation data
Epoch J2000.0      Equinox
Constellation Taurus
κ1 Tau
Right ascension 04h 25m 22.16505s[1]
Declination +22° 17′ 37.9375″[1]
Apparent magnitude (V) +4.22[2]
κ2 Tau
Right ascension 04h 25m 25.01518s[1]
Declination +22° 11′ 59.9876″[1]
Apparent magnitude (V) +5.24[2]
Characteristics
κ1 Tau
Spectral type A7IV-V[3]
U−B color index +0.12[2]
B−V color index +0.14[2]
κ2 Tau
Spectral type A7V
U−B color index +0.09[2]
B−V color index +0.17[2]
Astrometry
κ1 Tau
Radial velocity (Rv)+37.30[4] km/s
Proper motion (μ) RA: +105.10[1] mas/yr
Dec.: −45.04[1] mas/yr
Parallax (π)21.19 ± 0.21[1] mas
Distance154 ± 2 ly
(47.2 ± 0.5 pc)
Absolute magnitude (MV)+0.96[5]
κ2 Tau
Radial velocity (Rv)+32.00[6] km/s
Proper motion (μ) RA: +111.97[1] mas/yr
Dec.: −47.71[1] mas/yr
Parallax (π)22.03 ± 0.35[1] mas
Distance148 ± 2 ly
(45.4 ± 0.7 pc)
Absolute magnitude (MV)+2.18[5]
Details
κ1 Tau
Radius2.60[7] R☉
Luminosity33.6[8] L☉
Temperature9,000[7] K
Rotational velocity (v sin i)94[9] km/s
κ2 Tau
Luminosity11.8[8] L☉
Temperature7,400[8] K
Rotational velocity (v sin i)191[9] km/s
Other designations
κ Tau, ADS 3201
κ1 Tau: 65 Tauri, BD+21 642, HD 27934, HIP 20635, HR 1387, SAO 76601.[10]
κ2 Tau: 67 Tauri, BD+21 643, HD 27946, HIP 20641, HR 1388, SAO 76602.[11]
Database references
SIMBADκ1 Tau
κ2 Tau

System
Pleiades and Hyades with κ Tauri as the very close pair at lower centre (north is approximately to the left)

The system is dominated by a visual double star, κ1 Tauri and κ2 Tauri. κ1 Tauri is a white A-type subgiant with an apparent magnitude of +4.22.[2] It is emitting an excess of infrared radiation at a temperature indicating there is a circumstellar disk in orbit at a radius of 67 AU from the star.[7] κ2 Tauri is a white A-type main sequence star with an apparent magnitude of +5.24.[2]

Between the two bright stars is a binary star made up of two 9th magnitude stars, Kappa Tauri C and Kappa Tauri D, which are 5.5 arcseconds from each other (as of 2013) and 175.1 arcseconds from κ1 Tau. Two more 12th magnitude companions fill out the visual group: Kappa Tauri E, which is 145 arcseconds from κ1 Tau, and Kappa Tauri F, 108.5 arcseconds away from κ2 Tau.[12]

The bright pair are both members of the Hyades star cluster, while the fainter stars are all much more distant background stars.[13]

Test of General Relativity
One of the 1919 eclipse negatives, with κ1 and κ2 Tauri marked near the centre of the image

Kappa Tauri was photographed during the solar eclipse of May 29, 1919 by the expedition of Arthur Eddington in Príncipe and others in Sobral, Brazil that confirmed Albert Einstein's prediction of the bending of light around the Sun from his general theory of relativity which he published in 1915.[14]

Naming
  • With φ, υ and χ, it composed the Arabic were the Arabs' Al Kalbain, the Two Dogs.[15] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Kalbain were the title for five stars : φ as Alkalbain I, χ as Alkalbain II, these stars (κ2 and κ1) are Alkalbain III and Alkalbain IV, and υ as Alkalbain V.[16]
  • In Chinese, 天街 (Tiān Jiē), meaning Celestial Street, refers to an asterism consisting of κ1 Tauri and ω Tauri. Consequently, κ1 Tauri itself is known as 天街一 (Tiān Jiē yī, English: the First Star Star of Celestial Street.).[17]

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, S2CID 18759600.
  2. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data. SIMBAD, Bibcode:1986EgUBV........0M.
  3. Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819
  4. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35,495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
  5. Eggen, Olin J. (July 1998), "The Age Range of Hyades Stars", The Astronomical Journal, 116 (1): 284–292, Bibcode:1998AJ....116..284E, doi:10.1086/300413.
  6. Kharchenko, N. V.; et al. (2007), "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations", Astronomische Nachrichten, 328 (9): 889–896, arXiv:0705.0878, Bibcode:2007AN....328..889K, doi:10.1002/asna.200710776, S2CID 119323941.
  7. Rhee, Joseph H.; et al. (May 2007), "Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs", The Astrophysical Journal, 660 (2): 1556–1571, arXiv:astro-ph/0609555, Bibcode:2007ApJ...660.1556R, doi:10.1086/509912, S2CID 11879505.
  8. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
  9. Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298.
  10. "* kap01 Tau". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2015-11-05.
  11. "* kap02 Tau". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2015-11-05.
  12. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2015-11-08
  13. Horan, S. (November 1979), "A photometric survey of the Hyades for Delta Scuti variables", Astronomical Journal, 84: 1770–1774, Bibcode:1979AJ.....84.1770H, doi:10.1086/112607
  14. Dyson, F.W.; Eddington, A.S.; Davidson, C.R. (1920). "A Determination of the Deflection of Light by the Sun's Gravitational Field, from Observations Made at the Solar eclipse of May 29, 1919". Phil. Trans. Roy. Soc. A. 220 (571–581): 291–333. Bibcode:1920RSPTA.220..291D. doi:10.1098/rsta.1920.0009.
  15. Allen, Richard Hinckley (1899), Star-Names and Their Meanings, New York: G. E. Stechert, p. 413
  16. Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF), Jet Propulsion Laboratory, California Institute of Technology.
  17. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 23 日
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