Psi2 Aurigae

For other stars with this Bayer designation, see ψ Aurigae.

Psi² Aurigae is a star in the constellation Auriga. Its name is a Bayer designation that is Latinized from ψ² Aurigae, and abbreviated Psi² Aur or ψ² Aur. This star is faintly visible to the naked eye with an apparent visual magnitude of 4.79.^[3] Based upon parallax measurements, it is approximately 403 light-years (124 parsecs) away from the Earth.^[2] At that distance, the brightness of the star is diminished by 0.07 in magnitude from extinction caused by interstellar gas and dust.^[5] ψ² Aur is drifting further away from the Sun with a radial velocity of 16 km/s.^[5]

Psi² Aurigae

Location of ψ2 Aurigae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Auriga[1]
Right ascension	06h 39m 19.82724s[2]
Declination	+42° 29′ 19.9557″[2]
Apparent magnitude (V)	4.79[3]
Characteristics
Spectral type	K2- III[4]
U−B color index	+1.30[3]
B−V color index	+1.23[3]
R−I color index	0.6[citation needed]
Astrometry
Radial velocity (Rv)	16.09±0.19[5] km/s
Proper motion (μ)	RA: −0.576 mas/yr[2] Dec.: −55.657 mas/yr[2]
Parallax (π)	8.0927±0.1314 mas[2]
Distance	403 ± 7 ly (124 ± 2 pc)
Absolute magnitude (MV)	−0.72[1]
Details
Mass	4.1[2] M☉
Radius	31[2] R☉
Luminosity	304[1] L☉
Surface gravity (log g)	2.30[6] cgs
Temperature	4,410[6] K
Metallicity [Fe/H]	−0.10[6] dex
Rotational velocity (v sin i)	1.0[7] km/s
Age	372[8] Myr
Other designations
ψ2 Aur, 50 Aurigae, BD+42 1585, GC 8662, HD 47174, HIP 31832, HR 2427, SAO 41239, PPM 49219, WDS J06393+4229A[9]
Database references
SIMBAD	data

This is as a evolved K-type giant star with a stellar classification of K2 III.^[4] At an estimated age of 372 million years,^[8] it has exhausted the supply of hydrogen at its core and expanded to 31 times the radius of the Sun.^[2] It has 4.1 times the Sun's mass^[2] and is radiating 304 times the Sun's luminosity^[1] from its enlarged photosphere at an effective temperature of 4,410 K.^[6]

ψ² Aurigae was part of a much bigger constellation named Telescopium Herschelii. It was the constellation's second-brightest star before it fell out of use.^[10]