Psi4 Aurigae

Psi⁴ Aurigae is a single,^[10] orange-hued star in the northern constellation of Auriga. Its name is a Bayer designation that is Latinized from ψ⁴ Aurigae, and abbreviated Psi⁴ Aur or ψ⁴ Aur. This star is visible to the naked eye with an apparent visual magnitude of +5.02.^[3] With an annual parallax shift of 10.11 mas,^[2] it is approximately 323 light-years (99 parsecs) distant from Earth. The star is drifting closer to the Sun with a radial velocity of −77 km/s,^[5] and may approach to within 102 ly (31.3 pc) in around 1.1 million years.^[1]

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

Psi⁴ Aurigae

Location of ψ4 Aurigae (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Auriga[1]
Right ascension	06h 43m 04.972s[2]
Declination	+44° 31′ 28.02″[2]
Apparent magnitude (V)	+5.02[3]
Characteristics
Spectral type	K5 III[4]
U−B color index	+1.83[3]
B−V color index	+1.48[3]
Astrometry
Radial velocity (Rv)	−77.35±0.23[5] km/s
Proper motion (μ)	RA: −4.112 mas/yr[2] Dec.: −30.066 mas/yr[2]
Parallax (π)	10.1086±0.123 mas[2]
Distance	323 ± 4 ly (99 ± 1 pc)
Absolute magnitude (MV)	+0.06[1]
Details
Mass	1.03+0.79 −0.23[6] M☉
Radius	24.9[7] R☉
Luminosity	182+13 −12[6] L☉
Surface gravity (log g)	2.04±0.24[8] cgs
Temperature	4,020±80[6] K
Metallicity [Fe/H]	0.10±0.08[8] dex
Rotational velocity (v sin i)	4.8[5] km/s
Other designations
ψ4 Aur, 55 Aurigae, BD+44°1518, FK5 2517, GC 8751, HD 47914, HIP 32173, HR 2459, SAO 41288, PPM 49271[9]
Database references
SIMBAD	data

This is a evolved K-type giant star with a stellar classification of K5 III,^[4] having exhausted the hydrogen at its core. With nearly the same mass as the Sun,^[6] it has expanded to 25 times the Sun's radius. The star is radiating 182 times the Sun's luminosity from its enlarged photosphere at an effective temperature of about 4,158 K.^[6] It is spinning with a projected rotational velocity of 4.8 km/s.^[5] This is an α–enhanced star, displaying a significant enhancement of silicon in its atmosphere.^[11]

Psi⁴ Aurigae was part of a much bigger constellation named Telescopium Herschelii before that asterism was no longer recognized by the International Astronomical Union (IAU).^{[citation needed]}