Delta Draconis

Delta Draconis
Diagram showing star positions and boundaries of the Draco constellation and its surroundings


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
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] HR 7310, BD+67 1129, HD 180711, SAO 18222, FK5 723, HIP 94376.[11]

Delta Draconis (δ Dra, δ Draconis) is a yellow star in the constellation Draco. It has the traditional names Aldib, Altais[9] (the goat) and Nodus Secundus.[10] This star 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 Earth.[1]

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] 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.[12] 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.[13] With a mass 2.32[5] times that of the Sun, this star will end its life as a white dwarf.[10]

Etymology

The title Altais was derived from Arabic Al Tāis, "the Goat", the association of this star, along with π Dra, ρ Dra and ε Dra (Tyl).[14] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Tāis or Tais were the title for three stars :δ Dra as Altais, π Dra as Tais I and ρ Dra as Tais II (exclude ε Dra).[15]

In Chinese, 天廚 (Tiān Chú, Tien Choo), meaning Celestial Kitchen or Heaven's Kitchen, refers to an asterism consisting of δ Draconis, σ Draconis, ε Draconis, ρ Draconis, 64 Draconis and π Draconis.[16] Consequently, δ Draconis itself is known as 天廚一 (Tiān Chú yī, English: the First Star of Celestial Kitchen.)[17]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 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
  2. ↑ 2.0 2.1 2.2 2.3 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:1953QB901.W495.....
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 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
  6. ↑ 6.0 6.1 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. ↑ 7.0 7.1 7.2 7.3 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. ↑ 9.0 9.1 Bakich, Michael E. (1995). The Cambridge guide to the constellations. Cambridge University Press. p. 184. ISBN 0-521-44921-9.
  10. ↑ 10.0 10.1 10.2 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. ↑ 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.
  13. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16
  14. ↑ 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.
  15. ↑ 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.
  16. ↑ (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. ↑ (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.