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Pi Aurigae
	The location of π Aurigae (circled)
Observation data; Epoch J2000 Equinox J2000
Constellation	Auriga
Right ascension	05h 59m 56.09792s
Declination	+45° 56′ 12.2457″
Apparent magnitude (V)	4.25
Characteristics
Evolutionary stage	asymptotic giant branch
Spectral type	M3 II
U−B color index	+1.83
B−V color index	+1.72
Variable type	LC
Astrometry
Radial velocity (Rv)	0.71±0.76 km/s
Proper motion (μ)	RA: −3.755 mas/yr ; Dec.: −7.785 mas/yr
Parallax (π)	4.515 ± 0.241 mas
Distance	720 ± 40 ly ; (220 ± 10 pc)
Absolute magnitude (MV)	−2.46
Details
Radius	218.6 R☉
Luminosity	6,630±1,054 L☉
Surface gravity (log g)	0.55±0.10 cgs
Temperature	3,525±125 K
Metallicity [Fe/H]	0.03±0.04 dex
Other designations
	π Aur, 35 Aurigae, BD+45 1217, HD 40239, HIP 28404, HR 2091, SAO 40756
Database references
SIMBAD	data

Pi Aurigae, Latinized from π Aurigae, is the Bayer designation for a single,^[11] red-hued star in the northern constellation of Auriga. Located about one degree north of the 2nd magnitude star Beta Aurigae,^[12] Pi Aurigae is visible to the naked eye with an apparent visual magnitude of 4.25^[2] Based upon parallax measurements, it is approximately 720 light-years (220 parsecs) away from Earth.^[1] At that distance, the brightness of the star is diminished by 0.54 in magnitude from extinction caused by interstellar gas and dust.^[6]

Pi Aurigae is an evolved bright giant star with a stellar classification of M3 II.^[4] After exhausting the supply of hydrogen at its core the star has expanded to approximately 219 times the size of the Sun.^[8] It is classified as a slow irregular variable of type LC and its brightness varies from magnitude +4.24 to +4.34.^[5] On average, the star is radiating 6,630 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,525 K.^[8]

References

^ ^a ^b ^c ^d ^e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
^ ^a ^b ^c ^d Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
^ Eggen, Olin J. (July 1992), "Asymptotic giant branch stars near the sun", Astronomical Journal, 104 (1): 275–313, Bibcode:1992AJ....104..275E, doi:10.1086/116239.
^ ^a ^b Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics, 11 (1): 29, Bibcode:1973ARA&A..11...29M, doi:10.1146/annurev.aa.11.090173.000333.
^ ^a ^b Ruban, E. V.; et al. (September 2006), "Spectrophotometric observations of variable stars", Astronomy Letters, 32 (9): 604–607, Bibcode:2006AstL...32..604R, doi:10.1134/S1063773706090052, S2CID 121747360.
^ ^a ^b Famaey, B.; et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430 (1): 165–186, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272, S2CID 17804304.
^ 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.
^ ^a ^b ^c ^d ^e McDonald, I.; Zijlstra, A. A.; Watson, R. A. (2017-10-01), "Fundamental parameters and infrared excesses of Tycho-Gaia stars", Monthly Notices of the Royal Astronomical Society, 471 (1): 770–791, arXiv:1706.02208, Bibcode:2017MNRAS.471..770M, doi:10.1093/mnras/stx1433, ISSN 0035-8711 Pi Aurigae's database entry at VizieR.
^ ^a ^b Wu, Yue; et al. (January 2011), "Coudé-feed stellar spectral library - atmospheric parameters", Astronomy and Astrophysics, 525: A71, arXiv:1009.1491, Bibcode:2011A&A...525A..71W, doi:10.1051/0004-6361/201015014, S2CID 53480665.
^ "pi. Aur -- Pulsating variable Star", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2012-08-20.
^ 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.
^ O'Meara, Stephen James (2007), Steve O'Meara's Herschel 400 Observing Guide, Cambridge University Press, p. 23, ISBN 978-0521858939.