Delta Draconis

Delta Draconis (δ Draconis, abbreviated Delta Dra, δ Dra), formally named Altais /ælˈteɪ.ɪs/,[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. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 97.4 light-years (29.9 parsecs) from the Sun.[1]

δ Draconis
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 mas[1]
Distance97.4 ± 0.3 ly
(29.87 ± 0.09 pc)
Absolute magnitude (MV)+0.62[5]
Details
Mass2.32[5] M☉
Radius11[6] R☉
Luminosity59[5] L☉
Surface gravity (log g)2.98[7] cgs
Temperature4,820[7] K
Metallicity [Fe/H]–0.27[7] dex
Rotational velocity (v sin i)8[8] km/s
Age0.8[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]
Database references
SIMBADdata

Nomenclature

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).[13] 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).[14] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[15] 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 included in the List of IAU-approved 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.[16] Consequently, the Chinese name for Delta Draconis itself is 天廚一 (Tiān Chú yī, English: the First Star of Celestial Kitchen).[17]

Properties

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] it 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.[18] 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.[19] With a mass 2.32[5] times that of the Sun, this star will end its life as a white dwarf.[10]

Pole star

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

References
  1. van Leeuwen, F. (November 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. 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". Carnegie Institute Washington D.C. Publication. Washington: Carnegie Institution of Washington. Bibcode:1953GCRV..C......0W.
  5. 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:0805.2434, Bibcode:2008PASJ...60..781T, doi:10.1093/pasj/60.4.781, S2CID 16258166
  6. 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. Archived from the original on 2010-06-01. Retrieved 2010-04-06.
  7. 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. Bakich, Michael E. (1995). The Cambridge guide to the constellations. Cambridge University Press. p. 184. ISBN 0-521-44921-9.
  10. 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. "Naming Stars". IAU.org. Retrieved 4 March 2018.
  13. 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.
  14. 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.
  15. IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  16. (in 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.
  17. (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived October 25, 2008, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  18. 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.
  19. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 18, 2012, retrieved 2012-01-16
  20. "Dawn explores Ceres: Results from the survey orbit" (PDF). Archived from the original (PDF) on 2015-09-05. Retrieved 2017-03-30.
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