Pi Aurigae, a red bright giant star in Auriga
Pi Aurigae is a red bright giant star in the constellation Auriga. At 722 light years away, it shines at an apparent visual magnitude of 4.25.
Pi Aurigae (HIP 28404)
Pi Aurigae is a red bright giant star in the constellation Auriga. At 722 light years away, it shines at an apparent visual magnitude of 4.25. It is moving through the Galaxy at a speed of 9.1 km/s relative to the Sun.
Sky position: RA 5h 59.9m, Dec +45° 56.2'
Common designations: Pi Aurigae, 35 Aurigae, HR 2091, HD 40239, HIP 28404, Gaia DR3 196944217825405184
Pi Aurigae has the spectral type M3IIb. M-type stars are cool red stars below about 3,900 K whose spectra are dominated by titanium oxide molecular bands. Red dwarfs, red giants and red supergiants all fall in this class. Its luminosity class II marks it as a bright giant, more luminous than ordinary giants.
How to find Pi Aurigae in the sky
Pi Aurigae lies in Auriga. With a declination of +45° 56.2', it is visible from the entire Northern Hemisphere and from the Southern Hemisphere down to about latitude 44° S. Observers poleward of latitude 44° N see it as circumpolar: it never sets. It is bright enough to see with the naked eye under dark skies. It is highest in the sky at local midnight around January, which makes the weeks around that month the best time to observe it.
Tabulated data for Pi Aurigae
Astrometry and spectroscopy
| Right Ascension (J2000) | 89.98374136° (5h 59.9m) |
| Declination (J2000) | 45.93673492° (+45° 56.2') |
| Galactic Longitude | 166.60227463° |
| Galactic Latitude | 10.93723177° |
| Proper motion RA | -3.75 mas/yr |
| Proper motion Dec | -7.79 mas/yr |
| Parallax | 4.52 ± 0.24 mas |
| Spectral Type | M3IIb |
| Radial Velocity | 0.71 km/s |
Photometry
| Band | Magnitude | Abs. Mag. |
|---|---|---|
| U | 7.80 | 1.07 |
| B | 5.97 | -0.76 |
| V | 4.25 | -2.48 |
| R | 2.56 | -4.17 |
| I | 1.08 | -5.65 |
| J | 0.26 | -6.47 |
| H | -0.61 | -7.34 |
| K | -0.87 | -7.60 |
Colour index B-V: +1.72
Derivations
- Heliocentric distance: 221.46 pc (722 light years) (5.3% margin of error)
- Absolute visual magnitude: -2.48
- Transverse velocity: 9.1 km/s
- Space velocity relative to the Sun: 9.1 km/s
- Galactic position (X, Y, Z): -211.5 pc, 50.4 pc, 42.0 pc
- Galactic velocity (U, V, W): -3.3 km/s, -4.7 km/s, -7.0 km/s
Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.