Pi Puppis
Pi Puppis, Latinized from π Puppis, also named Ahadi, is the second-brightest star in the southern constellation of Puppis. It has an apparent visual magnitude of 2.733, so it can be viewed with the naked eye at night. Parallax measurements yield an estimated distance of roughly 810 light-years (250 parsecs) from the Earth. This is a double star with a magnitude 6.86 companion at an angular separation of 0.72 arcsecond and a position angle of 148° from the brighter primary.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Puppis |
| Right ascension | 07h 17m 08.55678s |
| Declination | −37° 05′ 50.8962″ |
| Apparent magnitude (V) | 2.733 |
| Characteristics | |
| Spectral type | K3 Ib |
| U−B color index | +1.238 |
| B−V color index | +1.608 |
| Variable type | SRd |
| Astrometry | |
| Radial velocity (Rv) | +15.8 km/s |
| Proper motion (μ) | RA: −10.05 mas/yr Dec.: +6.47 mas/yr |
| Parallax (π) | 4.04 ± 0.33 mas |
| Distance | 810 ± 70 ly (250 ± 20 pc) |
| Absolute magnitude (MV) | −4.5 |
| Details | |
| Mass | 11.7±0.2 M☉ |
| Radius | 235 R☉ |
| Luminosity | 11,378 L☉ |
| Surface gravity (log g) | 0.13 cgs |
| Temperature | 3,990–4,055 K |
| Age | 20.0±3.9 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
The spectrum of Pi Puppis matches a stellar classification of K3 Ib. The Ib luminosity class indicates this a lower luminosity supergiant star that has consumed the hydrogen fuel at its core, evolved away from the main sequence, and expanded to about 235 times the Sun's radius. The effective temperature of the star's outer envelope is approximately 4,000 K, which gives it the orange hue of a K-type star. It is a semiregular variable star that varies in apparent magnitude from a high of 2.70 down to 2.85. Pi Puppis is the brightest star in the open cluster Collinder 135.