Eta Piscium
Template:Location mark Location of η Piscium (circled) | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Pisces |
| Right ascension | Template:RA[1] |
| Declination | Template:DEC[1] |
| Apparent magnitude (V) | +3.611[2] (3.83 + 7.51)[3] |
| Characteristics | |
| Spectral type | G7 IIIa[4] |
| U−B Template:Engvar | +0.730[2] |
| B−V Template:Engvar | +0.976[2] |
| Variable type | γ Cas |
| Astrometry | |
| Radial velocity (Rv) | Script error: No such module "val".[5] km/s |
| Proper motion (μ) | RA: +27.14[1] mas/yr Dec.: −2.64[1] mas/yr |
| Parallax (π) | 9.33±0.72 mas[1] |
| Distance | Template:Rnd ± Template:Rnd ly (Template:Rnd ± Template:Rnd pc) |
| Absolute magnitude (MV) | −1.52[6] |
| Orbit[7] | |
| Period (P) | Script error: No such module "val". yr |
| Semi-major axis (a) | Script error: No such module "val".″ |
| Eccentricity (e) | Script error: No such module "val". |
| Inclination (i) | Script error: No such module "val".° |
| Longitude of the node (Ω) | Script error: No such module "val".° |
| Periastron epoch (T) | Script error: No such module "val". |
| Argument of periastron (ω) (secondary) | Script error: No such module "val".° |
| Details[5] | |
| η Psc A | |
| Mass | Script error: No such module "val". Template:Solar mass |
| Radius | Script error: No such module "val". Template:Solar radius |
| Luminosity | 457 Template:Solar luminosity |
| Surface gravity (log g) | Script error: No such module "val". cgs |
| Temperature | Script error: No such module "val". K |
| Metallicity [Fe/H] | Script error: No such module "val". dex |
| Rotational velocity (v sin i) | 8.4[8] km/s |
| Age | Script error: No such module "val". Myr |
| Metallicity [Fe/H] | {{{metal_fe2}}} dex |
| Other designations | |
| Alpherg, Template:Odlist[9] | |
| Database references | |
| SIMBAD | data |
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Eta Piscium (η Piscium, abbreviated Eta Psc, η Psc) is a binary star and the brightest star in the constellation of Pisces, with an apparent visual magnitude of +3.6.[2] Based upon a measured annual parallax shift of 9.33 mas as seen from Earth,[1] it is located roughly 350 light-years distant from the Sun in the thin disk population of the Milky Way.[5]
The two components are designated Eta Piscium A (formally named Alpherg Template:IPAc-en, the traditional name of the system)[10] and B.
Nomenclature
η Piscium (Latinised to Eta Piscium) is the system's Bayer designation. The designations of the two constituents as Eta Piscium A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[11]
The system bore the traditional names Al Pherg (in this context meaning the emptying) and Kullat Nunu. At the time that the Sun at the March Equinox entered into Pisces having lay in Aries, the system was in the first ecliptic constellation of the Neo-Babylonians, Kullat Nūnu − Nūnu being Babylonian for fish and Kullat referring to either the bucket or the cord that binds the fish.[12] In 2016, the IAU organized a Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[14] It approved the name Alpherg for the component Eta Piscium A on 1 June 2018 (for its official List).[10]
In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Official in Charge of the Pasturing, refers to an asterism consisting of Eta Piscium, Rho Piscium, Pi Piscium, Omicron Piscium and 104 Piscium. Consequently, the Chinese name for Eta Piscium itself is Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx.)[15]
Properties
At its present distance, the visual magnitude of the system is diminished by an extinction factor of Script error: No such module "val". due to interstellar dust.
This system's binary nature was discovered in 1878 by an amateur astronomer, S. W. Burnham.[7] It has an orbital period of roughly 850 years, a semimajor axis of 1.2 arc seconds, and an eccentricity of 0.47.
The primary, component A, is an evolved, magnitude 3.83[3] G-type giant star with a stellar classification of G7 IIIa.[4] It has a weak magnetic field with a strength of Script error: No such module "val".,[8] and is a Gamma Cassiopeiae variable.[7] The companion, component B, is a magnitude 7.51 star.[3]
References
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- ↑ Template:Cite simbad
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- ↑ Template:In lang AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 19 日 Template:Webarchive
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External links
- Script error: No such module "citation/CS1".