| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cassiopeia |
| Right ascension | 02h 49m 44.4867s[1] |
| Declination | +71° 45′ 11.6322″[1] |
| Apparent magnitude (V) | 8.17[2] |
| Characteristics | |
| Spectral type | G0IV[3] |
| Apparent magnitude (B) | 8.76[2] |
| Apparent magnitude (V) | 8.17[2] |
| Astrometry | |
| Radial velocity (Rv) | −3.15 ± 0.20[4] km/s |
| Proper motion (μ) | RA: 90.982±0.064[1]mas/yr Dec.: −33.197±0.062[1]mas/yr |
| Parallax (π) | 12.7776±0.0389 mas[1] |
| Distance | 255.3 ± 0.8 ly (78.3 ± 0.2 pc) |
| Absolute magnitude (MV) | 3.70 |
| Details | |
| Mass | 1.275 ± 0.018[5] M☉ |
| Radius | 1.5007 ± 0.0076[5] R☉ |
| Temperature | 6079 ± 80[6] K |
| Metallicity [Fe/H] | 0.24 ± 0.05[6] dex |
| Age | 3.37+0.20 −0.47[5] Gyr |
| Other designations | |
| Nushagak,BD+71°171,HIP 13192,SAO 4737,GSC 04321-01320,PPM 5099,TYC 4321-1320-1,AG+71 95[2] | |
| Database references | |
| SIMBAD | data |
HD 17156, namedNushagak by theIAU,[7] is ayellow subgiantstar approximately 255light-years away in theconstellation ofCassiopeia. Theapparent magnitude is 8.17, which means it is not visible to thenaked eye but can be seen with goodbinoculars.[2] A search for a binary companion star usingadaptive optics at theMMT Observatory was negative.[8]
The star is more massive and larger than theSun while Itsabsolute magnitude of 3.70 andspectral type of G0, show that it is both hotter and moreluminous. Based onasteroseismic 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 ismetal-rich.[3][5]
Anextrasolar planet,HD 17156 b, was discovered with the radial velocity method in 2007, and subsequently was observed totransit the star. At the time it was the transiting planet with the longest period.[3][9]
The star was given the nameNushagak by theIAU, chosen by United States representatives for theNameExoWorlds 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."[7] HD 17156 b was given the designationMulchatna, asMulchatna is a tributary of the Nushagak river.
It is the first star in Cassiopeia around which an orbitingplanet was discovered (in 2007) using theradial velocity method. Later observations showed that this planet alsotransited the star.[9] In February 2008, a second planet was proposed, with a 5:1 mean motion resonance to the inner planet HD 17156 b, though in 2017 this planet candidate was retracted.[10]
| 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 | — | — |
OUTDATED, REJECTED AND CANNOT BE PUBLISHED. DOES NOT INCLUDE VARIOUS ADVANCEMENTS IN THE FIELD (REPORTED IN OTHER PUBLICATIONS). NEED MORE DATA OBTAINED, AT WHICH POINT A COMPLETELY NEW PAPER WILL BE WRITTEN. PLEASE SCRAP
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