Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Cassiopeia [1] |
Right ascension | 02h 49m 44.48710s [2] |
Declination | +71° 45′ 11.6292″ [2] |
Apparent magnitude (V) | 8.16 [3] |
Characteristics | |
Evolutionary stage | main sequence [2] |
Spectral type | F9V [4] |
Astrometry | |
Radial velocity (Rv) | −3.15±0.20 [5] km/s |
Proper motion (μ) | RA: +90.848 [2] mas/yr Dec.: −33.013 [2] mas/yr |
Parallax (π) | 12.9142±0.0177 mas [2] |
Distance | 252.6 ± 0.3 ly (77.4 ± 0.1 pc) |
Absolute magnitude (MV) | 3.80 [1] |
Details | |
Mass | 1.275±0.018 [6] M☉ |
Radius | 1.5007±0.0076 [6] R☉ |
Luminosity | 2.6 [2] L☉ |
Surface gravity (log g) | 4.17 [2] cgs |
Temperature | 6,079±80 [7] K |
Metallicity [Fe/H] | 0.24±0.05 [7] dex |
Age | 3.37+0.20 −0.47 [6] Gyr |
Other designations | |
Nushagak, BD+71°171, HIP 13192, SAO 4737, GSC 04321-01320, PPM 5099, TYC 4321-1320-1, AG+71 95 [8] | |
Database references | |
SIMBAD | data |
HD 17156, named Nushagak by the IAU, [9] 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. [8] A search for a binary companion star using adaptive optics at the MMT Observatory was negative. [10]
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. [11] [12]
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. [11] [6]
The star was given the name Nushagak by the IAU, chosen by United States representatives for the NameExoWorlds content, with the comment that "Nushagak is a regional river near Dilingham, Alaska, which is famous for its wild salmon that sustain local Indigenous communities." [9] HD 17156 b was given the designation Mulchatna, as Mulchatna is a tributary of the Nushagak river.
It is the first star in Cassiopeia around which an orbiting planet was discovered (in 2007) using the radial velocity method. Later observations showed that this planet also transited the star. [12]
Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
b / Mulchatna | 3.235±0.032 MJ | 0.16278±0.00076 | 21.2163979±0.0000159 | 0.6703+0.0014 −0.0013 | — | — |