Delta 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[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] |
| 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 | |
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]
[edit] 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]
[edit] 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]
[edit] References
- ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, Bibcode 2007A&A...474..653V, doi:10.1051/0004-6361:20078357
- ^ a b c d Johnson, H. L.; Mitchell; Iriarte; Wisniewski; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory 4 (99): 99. Bibcode 1966CoLPL...4...99J.
- ^ 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.
- ^ Wilson, Ralph Elmer (1953). General Catalogue of Stellar Radial Velocities. Washington: Carnegie Institution of Washington. Bibcode 1953QB901.W495......
- ^ 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, Bibcode 2008PASJ...60..781T
- ^ a b The Sun has a radius of 0.004652 AU. Thus: See: Lochner, Jim; Gibb, Meredith; Newman, Phil (January 30, 2006). "Using Optical Observations to find the Diameter of HT Cas". NASA. http://imagine.gsfc.nasa.gov/YBA/HTCas-size/optical.html. Retrieved 2010-04-06.
- ^ 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.
- ^ Bernacca, P. L.; Perinotto, M.; Perinotto (1970). "A catalogue of stellar rotational velocities". Contributi Osservatorio Astronomico di Padova in Asiago 239 (1): 1. Bibcode 1970CoAsi.239....1B.
- ^ a b Bakich, Michael E. (1995). The Cambridge guide to the constellations. Cambridge University Press. p. 184. ISBN 0521449219.
- ^ a b c Kaler, James B.. "Nodus Secundus". STARS. University of Illinois. http://stars.astro.illinois.edu/sow/nodus2.html. Retrieved 2010-04-06.
- ^ "del Dra -- Star in double system". SIMBAD. Centre de Données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=del+Dra. Retrieved 2010-04-06.
- ^ 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.
- ^ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html, retrieved 2012-01-16
- ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 209. ISBN 0486210790. http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Draco*.html. Retrieved 2010-12-12.
- ^ Rhoads, Jack W. (November 15, 1971). "Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars". Jet Propulsion Laboratory, California Institute of Technology. http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720005197_1972005197.pdf.
- ^ (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 9789867332257.
- ^ (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.
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