Delta Aurigae

Delta Aurigae (δ Aur, δ Aurigae) is the Bayer designation for an astrometric binary[7] star in the constellation Auriga. It is visible to the naked eye with an apparent visual magnitude of 3.715.[2] Based upon its annual parallax shift of 25.88 mas,[1] it is some 126 light-years (39 parsecs) distant from the Earth, give or take an eight light-year margin of error. This star is the namesake for the Delta Aurigids, a meteor shower that occurs between October 6–15.[8] The radiant point for this shower passes several degrees to the south of the star.[9]

Delta Aurigae

Location of δ Aurigae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Auriga
Right ascension 05h 59m 31.63201s[1]
Declination +54° 17′ 04.7703″[1]
Apparent magnitude (V) 3.715[2]
Characteristics
Spectral type K0 III[3]
U−B color index +0.837[2]
B−V color index +1.017[2]
R−I color index 0.5
Astrometry
Radial velocity (Rv)+8.2[4] km/s
Proper motion (μ) RA: +81.81[1] mas/yr
Dec.: –132.98[1] mas/yr
Parallax (π)25.88 ± 1.61[1] mas
Distance126 ± 8 ly
(39 ± 2 pc)
Details
Radius11[5] R☉
Luminosity62[5] L☉
Surface gravity (log g)2.7[5] cgs
Temperature4,786[5] K
Metallicity [Fe/H]–0.15[5] dex
Rotational velocity (v sin i)3.9[5] km/s
Other designations
33 Aurigae, BD+54 970, FK5 225, HD 40035, HIP 28358, HR 2077, SAO 25502.[6]
Database references
SIMBADdata

Delta Aurigae is a spectroscopic binary: periodic Doppler shifts in the star's spectrum indicate orbital motion. The visible component of this system is a giant star with a stellar classification of K0 III.[3] It has 11 times the radius of the Sun and shines with 62 times the Sun's luminosity. This energy is being radiated from the star's outer envelope at an effective temperature of 4,786 K.[5] This heat gives the star the orange-hued glow of a K-type star.[10] Delta Aurigae has an orbital period of 1,283.4 days (3.514 years) and an eccentricity of 0.231.[11]

Name

In Indian astronomy, it is known by the name Prajapati /prəˈdʒɑːpəti/, from the Sanskrit प्रजापति prajāpati "the Lord of Created Beings".[12][13]

In Chinese, 八穀 (Bā Gǔ), meaning Eight Kinds of Crops, refers to an asterism consisting of δ Aurigae, ξ Aurigae, 26 Camelopardalis, 14 Camelopardalis, 7 Camelopardalis, 9 Aurigae, 11 Camelopardalis and 31 Camelopardalis.[14] Consequently, the Chinese name for δ Aurigae itself is 八穀一 (Bā Gǔ yī, English: the First Star of Eight Kinds of Crops), refers to the rice.

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. Oja, T. (August 1986), "UBV photometry of stars whose positions are accurately known. III", Astronomy and Astrophysics Supplement Series, 65 (2): 405–409, Bibcode:1986A&AS...65..405O.
  3. Eggen, O. J. (1962), "Space-velocity vectors for 3483 stars with proper motion and radial velocity", Royal Observatory Bulletin, 51: 79, Bibcode:1962RGOB...51...79E.
  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. Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
  6. "del Aur". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-08-18.
  7. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  8. Reynolds, Mike D. (2010), Falling Stars: A Guide to Meteors and Meteorites, Haunted Series (2nd ed.), Stackpole Books, p. 42, ISBN 978-0811736169
  9. Lunsford, Robert (2008), Meteors and How to Observe Them, Astronomers' Observing Guides, Springer, p. 86, ISBN 978-0387094601
  10. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-10, retrieved 2012-01-16
  11. Pourbaix, D.; et al. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics. 424 (2): 727–732. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213. S2CID 119387088.
  12. "Auriga", by Richard Hinckley Allen in Star Names: Their Lore and Meaning
  13. Monier-Williams Sanskrit dictionary: pra-cchana—pra-jalpa
  14. (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.
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