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Delta Aurigae

Location of δ Aurigae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Auriga
Right ascension	05 59 31.61842
Declination	+54° 17′ 05.0567″
Apparent magnitude (V)	3.715
Characteristics
Spectral type	K0 IIIb
U−B color index	+0.837
B−V color index	+1.017
R−I color index	0.5
Astrometry
Radial velocity (Rv)	+9.75±0.44 km/s
Proper motion (μ)	RA: +85.814 mas/yr Dec.: −142.928 mas/yr
Parallax (π)	23.0557 ± 0.4512 mas
Distance	141 ± 3 ly (43.4 ± 0.8 pc)
Absolute magnitude (MV)	0.56
Orbit
Period (P)	1,283.4±0.7 d
Semi-major axis (a)	≥ 39.1 ± 0.8 Gm (0.2614 ± 0.0053 AU)
Eccentricity (e)	0.231±0.017
Periastron epoch (T)	52,980±16 MJD
Argument of periastron (ω) (secondary)	200±5°
Semi-amplitude (K1) (primary)	2.28±0.04 km/s
Details
Mass	1.63 M☉
Radius	11 R☉
Luminosity	62 L☉
Surface gravity (log g)	2.7 cgs
Temperature	4,786 K
Metallicity	−0.15 dex
Rotational velocity (v sin i)	3.9 km/s
Age	3.26 Gyr
Other designations
δ Aur, 33 Aurigae, BD+54 970, FK5 225, HD 40035, HIP 28358, HR 2077, SAO 25502
Database references
SIMBAD	data

Delta Aurigae, Latinized from δ Aurigae, is the Bayer designation for an astrometric binary star in the northern constellation of Auriga. It is visible to the naked eye with an apparent visual magnitude of 3.715. Based upon its annual parallax shift of 23.06 mas, it is some 141 light-years (43 parsecs) distant from the Earth, give or take a three light-year margin of error. It is drifting further away with a radial velocity of +10 km/s. This star is the namesake for the Delta Aurigids, a meteor shower that occurs between October 6–15. The radiant point for this shower passes several degrees to the south of the star.

The variable radial velocity of this system was not recognized until 1999, more than a century following the first measurement in 1897. Delta Aurigae is a single-lined spectroscopic binary: periodic Doppler shifts in the star's spectrum indicate orbital motion. The pair have an orbital period of 1,283.4 days (3.514 years) and an eccentricity of 0.231. Based on the small amplitude of the radial velocity variation, the companion is most likely a small K- or early M-type main-sequence star with around half the mass of the Sun.

The visible component of this system is an evolved giant star with a stellar classification of K0 IIIb. It is a red clump star, indicating that it is generating energy through helium fusion at its core. The star is 3.26 billion years old and is spinning with a projected rotational velocity of 4 km/s. It has 1.63 times the mass of the Sun and has expanded to 11 times the Sun's radius. The star is radiating 62 times the Sun's luminosity from the star's photosphere at an effective temperature of 4,786 K. This heat gives the star the orange-hued glow of a K-type star.

Name

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

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. 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. ^ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
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. ^ Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
4. ^ 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.
5. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
6. ^ Griffin, R. F. (April 2009), "Spectroscopic binary orbits from photoelectric radial velocities. Paper 205: HD 9519, delta Aurigae, HR 4427, and HR 7795", The Observatory, 129: 54–79, Bibcode:2009Obs...129...54G.
7. ^ Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 23, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID 118505114, 88.
8. ^ 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, S2CID 121883397.
9. "del Aur". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-08-18.
10. 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.
11. Reynolds, Mike D. (2010), Falling Stars: A Guide to Meteors and Meteorites, Haunted Series (2nd ed.), Stackpole Books, p. 42, ISBN 978-0811736169
12. Lunsford, Robert (2008), Meteors and How to Observe Them, Astronomers' Observing Guides, Springer, p. 86, ISBN 978-0387094601
13. Alves, David R. (August 2000), "K-Band Calibration of the Red Clump Luminosity", The Astrophysical Journal, 539 (2): 732–741, arXiv:astro-ph/0003329, Bibcode:2000ApJ...539..732A, doi:10.1086/309278, S2CID 16673121.
14. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-18, retrieved 2012-01-16
15. "Auriga", by Richard Hinckley Allen in Star Names: Their Lore and Meaning
16. Monier-Williams Sanskrit dictionary: pra-cchana—pra-jalpa
17. (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.

External links

• HR 2077
• CCDM J05595+5418
• Image Delta Aurigae
• The Constellations and Named Stars
• Star Register

v t e Constellation of Auriga
Auriga in Chinese astronomy List of stars in Auriga
Stars	Bayer α (Capella) β (Menkalinan) γ (Elnath) δ ε (Almaaz) ζ (Saclateni) η (Haedus) θ (Mahasim) ι (Hassaleh) κ λ (Alhurr) μ ν ξ ο π ρ σ τ υ φ χ ψ ψ ψ ψ ψ ψ ψ ψ ψ ω Flamsteed 2 5 6 9 12 14 16 18 19 22 26 28 36 38 39 40 41 42 43 45 47 49 51 53 54 59 60 62 63 64 65 66 35 Cam Variable R T RT (48) RW SU UU WW AB AE AR (17) EO IQ IU LY MZ NO NY PU QZ V352 V361 V394 V420 V433 V538 HR 1558 1615 1738 1752 1794 1795 1822 1825 1866 1884 1938 1945 2028 2096 2137 HD 33203 33463 35619 43691 45350 (Lucilinburhuc) 49674 (Nervia) Other Gliese 268 HAT-P-9 (Tevel) KELT-2 MWC 480 SGR 0501+4516 UGPS J0521+3640 WASP-12
Exoplanets HAT-P-9b (Alef) HD 40979 b HD 43691 b HD 45350 b HD 49674 b KELT-2Ab WASP-12b
Star clusters	NGC 1664 1893 1907 1931 2240 2281 Other Messier 36 Messier 37 Messier 38 Palomar 2
Nebulae	NGC 1985 2242 Other IC 405 IC 2149 Westbrook Nebula
Galaxies 3C 147 4C +41.17 DA 193 MCG +08-11-011
Galaxy clusters MACS J0717.5+3745
Category

• K-type giants
• Horizontal-branch stars
• Spectroscopic binaries
• Astrometric binaries
• Auriga
• Bayer objects
• Durchmusterung objects
• Flamsteed objects
• Henry Draper Catalogue objects
• Hipparcos objects
• Bright Star Catalogue objects
• Stars with proper names