Psi4 Aurigae
Star in the constellation Auriga
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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]
 | |
| 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]