Pi Aurigae
Star in the constellation Auriga
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Pi Aurigae is a single,[12] 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,[13] 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]
 | |
| 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 | |
| Mass | 2.98[8] M☉ |
| Radius | 218.6[9] R☉ |
| Luminosity | 6,630±1,054[9] L☉ |
| Surface gravity (log g) | 0.55±0.10[10] cgs |
| Temperature | 3,525±125[9] K |
| Metallicity [Fe/H] | 0.03±0.04[10] dex |
| Other designations | |
| π Aur, 35 Aurigae, BD+45 1217, HD 40239, HIP 28404, HR 2091, SAO 40756[11] | |
| Database references | |
| SIMBAD | data |
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.[9] 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.[9]