Delta Draconis

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Delta Draconis
Diagram showing star positions and boundaries of the Draco constellation and its surroundings
Cercle rouge 100%.svg

Location of δ Draconis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension 19h 12m 33.30197s[1]
Declination +67° 39′ 41.5456″[1]
Apparent magnitude (V) 3.07[2]
Characteristics
Spectral type G9 III[3]
U−B color index +0.78[2]
B−V color index +1.00[2]
Astrometry
Radial velocity (Rv) +24.8[4] km/s
Proper motion (μ) RA: +95.74[1] mas/yr
Dec.: +91.92[1] mas/yr
Parallax (π) 33.48 ± 0.10[1] mas
Distance 97.4 ± 0.3 ly
(29.87 ± 0.09 pc)
Absolute magnitude (MV) +0.62[5]
Details
Mass 2.32[5] M
Radius 11[6] R
Luminosity 59[5] L
Surface gravity (log g) 2.98[7] cgs
Temperature 4,820[7] K
Metallicity [Fe/H] –0.27[7] dex
Rotational velocity (v sin i) 8[8] km/s
Age 0.8[5] Gyr
Other designations
Aldib, Altais,[9] Nodus Secundus,[10] 57 Draconis, HR 7310, BD+67 1129, HD 180711, SAO 18222, FK5 723, HIP 94376.[11]

Delta Draconis (δ Draconis, abbreviated Delta Dra, δ Dra), also named Altais,[12] is a yellow star in the constellation of Draco. It has an apparent visual magnitude of 3.0,[2] making it easily visible to the naked eye. Parallax measurements with the Hipparcos satellite yield a distance estimate of 97.4 light-years (29.9 parsecs) from the Sun.[1]

Properties[edit]

Delta Draconis is a giant star with a stellar classification of G9 III. This indicates that, at an estimated age of 800 million years,[5] this star has exhausted the supply of hydrogen at its core and entered a later stage in its evolution. The angular diameter of the star is estimated as 3.37 ± 0.06 mas.[13] At a parallax of 32.54 mas, this corresponds to a physical radius equal to 11 times the solar radius.[6] It is radiating 59[5] times the luminosity of the Sun from its outer atmosphere at an effective temperature of 4,820 K.[7] At this temperature, it is giving off the yellow-hued glow of a G-type star.[14] With a mass 2.32[5] times that of the Sun, this star will end its life as a white dwarf.[10]

Etymology[edit]

δ Draconis (Latinised to Delta Draconis) is the star's Bayer designation.

It bore the traditional names Aldib, Altais[9] (the goat) and Nodus Secundus.[10] The title Altais was derived from Arabic Al Tāis "the Goat", the association of this star, along with Pi Draconis, Rho Draconis and Epsilon Draconis (Tyl).[15] According to a 1971 NASA catalog of stars, Al Tāis or Tais were the title for three stars : Delta Draconis as Altais, Pi Draconis as Tais I and Rho Draconis]] as Tais II (exclude Epsilon Draconis).[16] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[17] to catalogue and standardize proper names for stars. The WGSN approved the name Altais for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.[12]

In Chinese, 天廚 (Tiān Chú, Tien Choo), meaning Celestial Kitchen or Heaven's Kitchen, refers to an asterism consisting of Delta Draconis, Sigma Draconis, Epsilon Draconis, Rho Draconis, 64 Draconis and Pi Draconis.[18] Consequently, Delta Draconis itself is known as 天廚一 (Tiān Chú yī, English: the First Star of Celestial Kitchen.)[19]

Pole star[edit]

Delta Draconis is the northern pole star of Ceres, lying 1.5 degrees from the true pole.[20]

References[edit]

  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c d Johnson, H. L.; Mitchell; Iriarte; Wisniewski (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J. 
  3. ^ Roman, Nancy G. (July 1952). "The Spectra of the Bright Stars of Types F5-K5". Astrophysical Journal. 116: 122. Bibcode:1952ApJ...116..122R. doi:10.1086/145598. 
  4. ^ Wilson, Ralph Elmer (1953). General Catalogue of Stellar Radial Velocities. Washington: Carnegie Institution of Washington. Bibcode:1953GCRV..C......0W. 
  5. ^ a b c d e f g Takeda, Yoichi; et al. (August 2008), "Stellar Parameters and Elemental Abundances of Late-G Giants", Publications of the Astronomical Society of Japan, 60 (4): 781–802, arXiv:0805.2434Freely accessible, Bibcode:2008PASJ...60..781T, doi:10.1093/pasj/60.4.781 
  6. ^ a b The Sun has a radius of 0.004652 AU. Thus:
    Stellar diameter = 1 AU × angular diameter/parallax = 3.37/32.54 AU = 0.10 AU = 22 R.
    See: Lochner, Jim; Gibb, Meredith; Newman, Phil (January 30, 2006). "Using Optical Observations to find the Diameter of HT Cas". NASA. Retrieved 2010-04-06. 
  7. ^ a b c d McWilliam, Andrew (December 1990). "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances". Astrophysical Journal Supplement Series. 74: 1075–1128. Bibcode:1990ApJS...74.1075M. doi:10.1086/191527. 
  8. ^ Bernacca, P. L.; Perinotto, M. (1970). "A catalogue of stellar rotational velocities". Contributi Osservatorio Astronomico di Padova in Asiago. 239 (1): 1. Bibcode:1970CoAsi.239....1B. 
  9. ^ a b Bakich, Michael E. (1995). The Cambridge guide to the constellations. Cambridge University Press. p. 184. ISBN 0-521-44921-9. 
  10. ^ a b c Kaler, James B. "Nodus Secundus". STARS. University of Illinois. Retrieved 2010-04-06. 
  11. ^ "del Dra -- Star in double system". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2010-04-06. 
  12. ^ a b "IAU Catalog of Star Names". Retrieved 28 July 2016. 
  13. ^ Di Benedetto, G. P. (February 2005). "Predicting accurate stellar angular diameters by the near-infrared surface brightness technique". Monthly Notices of the Royal Astronomical Society. 357 (1): 174–190. Bibcode:2005MNRAS.357..174D. doi:10.1111/j.1365-2966.2005.08632.x. 
  14. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16 
  15. ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 209. ISBN 0-486-21079-0. Retrieved 2010-12-12. 
  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. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016. 
  18. ^ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  19. ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
  20. ^ Dawn explores Ceres: Results from the survey orbit (cached version)