HD 17156
HD 17156, named Nushagak by the IAU, is a yellow subgiant star approximately 255 light-years away in the constellation of Cassiopeia. The apparent magnitude is 8.17, which means it is not visible to the naked eye but can be seen with good binoculars. A search for a binary companion star using adaptive optics at the MMT Observatory was negative.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cassiopeia |
| Right ascension | 02h 49m 44.4867s |
| Declination | +71° 45′ 11.6322″ |
| Apparent magnitude (V) | 8.17 |
| Characteristics | |
| Spectral type | G0IV |
| Apparent magnitude (B) | 8.76 |
| Apparent magnitude (V) | 8.17 |
| Astrometry | |
| Radial velocity (Rv) | −3.15 ± 0.20 km/s |
| Proper motion (μ) | RA: 90.982±0.064 mas/yr Dec.: −33.197±0.062 mas/yr |
| Parallax (π) | 12.7776 ± 0.0389 mas |
| Distance | 255.3 ± 0.8 ly (78.3 ± 0.2 pc) |
| Absolute magnitude (MV) | 3.70 |
| Details | |
| Mass | 1.275 ± 0.018 M☉ |
| Radius | 1.5007 ± 0.0076 R☉ |
| Temperature | 6079 ± 80 K |
| Metallicity [Fe/H] | 0.24 ± 0.05 dex |
| Age | 3.37 +0.20 −0.47 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
The star is more massive and larger than the Sun while Its absolute magnitude of 3.70 and spectral type of G0, show that it is both hotter and more luminous. Based on asteroseismic density constraints and stellar isochrones, it was found that the age is 3.37 +0.20
−0.47 billion years making it about two thirds as old as the Sun. Spectral observations show that the star is metal-rich.
An extrasolar planet, HD 17156 b, was discovered with the radial velocity method in 2007, and subsequently was observed to transit the star. At the time it was the transiting planet with the longest period.