Pi Aurigae

Pi Aurigae is a single,^[11] red-hued star in the northern constellation of Auriga. Its name is a Bayer designation that is Latinized from π Aurigae, and abbreviated Pi Aur or π Aur. 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^[3] Based upon parallax measurements, it is approximately 720 light-years (220 parsecs) away from Earth.^[2] At that distance, the brightness of the star is diminished by 0.54 in magnitude from extinction caused by interstellar gas and dust.^[7]

Pi Aurigae

The location of π Aurigae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Auriga[1]
Right ascension	05h 59m 56.09792s[2]
Declination	+45° 56′ 12.2457″[2]
Apparent magnitude (V)	4.25[3]
Characteristics
Evolutionary stage	asymptotic giant branch[4]
Spectral type	M3 IIb[5]
U−B color index	+1.83[3]
B−V color index	+1.72[3]
Variable type	LC[6]
Astrometry
Radial velocity (Rv)	0.71±0.76[7] km/s
Proper motion (μ)	RA: −3.755 mas/yr[2] Dec.: −7.785 mas/yr[2]
Parallax (π)	4.515±0.241 mas[2]
Distance	720 ± 40 ly (220 ± 10 pc)
Absolute magnitude (MV)	−2.46[1]
Details
Radius	218.6[8] R☉
Luminosity	6,630±1,054[8] L☉
Surface gravity (log g)	0.55±0.10[9] cgs
Temperature	3,525±125[8] K
Metallicity [Fe/H]	0.03±0.04[9] dex
Other designations
π Aur, 35 Aurigae, BD+45 1217, HD 40239, HIP 28404, HR 2091, SAO 40756[10]
Database references
SIMBAD	data

π Aurigae (center) in optical light

Pi Aurigae is an evolved bright giant star with a stellar classification of M3 IIb.^[5] 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.^[6] 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]