Phi Aurigae

Phi Aurigae is a giant star in the northern constellation of Auriga. Its name is a Bayer designation that is Latinized from φ Aurigae, and abbreviated Phi Aur or φ Aur. This star is faintly visible to the naked eye with an apparent visual magnitude of 5.089.^[3] It lies 10′ from another faint naked-eye star HD 35520, between the three open clusters M36 and M38, and NGC 1893.

φ Aurigae

Location of φ Aurigae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Auriga[1]
Right ascension	05h 27m 38.884s[2]
Declination	+34° 28′ 33.17″[2]
Apparent magnitude (V)	5.089[3]
Characteristics
Spectral type	K3 IIIp[4]
U−B color index	+1.649[3]
B−V color index	+1.411[3]
R−I color index	0.47[citation needed]
Astrometry
Radial velocity (Rv)	+30.78±0.21[5] km/s
Proper motion (μ)	RA: −1.050 mas/yr[2] Dec.: −38.934 mas/yr[2]
Parallax (π)	6.4359±0.1095 mas[2]
Distance	507 ± 9 ly (155 ± 3 pc)
Absolute magnitude (MV)	−0.62[1]
Details
Radius	33.97±1.05[6] R☉
Luminosity	307±15[6] L☉
Surface gravity (log g)	1.75[4] cgs
Temperature	4,222[6] K
Metallicity [Fe/H]	−0.03[4] dex
Rotational velocity (v sin i)	1.6[7] km/s
Other designations
φ Aur, 24 Aurigae, BD+34 1048, HD 35620, HIP 25541, HR 1805, SAO 58051[8]
Database references
SIMBAD	data

φ Aurigae in optical light

The distance to this star, as determined from parallax measurements, is approximately 507 light-years (155 parsecs) with a 9 light-year margin of error.^[2] It is drifting further away from the Sun with a radial velocity of +31 km/s.^[5]

This is an evolved giant star with a stellar classification of K3 IIIp.^[4] Having exhausted the supply of hydrogen at its core, it has expanded to 34 times the radius of the Sun. It is radiating over 300^[6] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,222 K,^[6] giving it the cool orange-hued glow of a K-type star.