Eta Piscium

Eta Piscium
Location of η Piscium (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Pisces
Right ascension 01h 31m 29.01026s[1]
Declination +15° 20′ 44.9685″[1]
Apparent magnitude (V) +3.611[2] (3.83 + 7.51)[3]
Characteristics
Spectral type G7 IIIa[4]
U−B color index +0.730[2]
B−V color index +0.976[2]
Variable type γ Cas
Astrometry
Radial velocity (Rv)13.60±0.42[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]
Distance350 ± 30 ly
(107 ± 8 pc)
Absolute magnitude (MV)−1.52[6]
Orbit[7]
Period (P)850.5±66.5 yr
Semi-major axis (a)1.228±0.144″
Eccentricity (e)0.469±0.053
Inclination (i)58.5±2.5°
Longitude of the node (Ω)32.8±2.0°
Periastron epoch (T)2040.3±66.9
Argument of periastron (ω)
(secondary)		86.9±4.0°
Details[5]
η Psc A
Mass3.78±0.16 M☉
Radius26.48±2.15 R☉
Luminosity457 L☉
Surface gravity (log g)2.20±0.14 cgs
Temperature4,937±40 K
Metallicity [Fe/H]−0.13±0.06 dex
Rotational velocity (v sin i)8.4[8] km/s
Age220±30 Myr
Other designations
Alpherg, η Psc, 99 Piscium, BD+14° 231, FK5 50, HD 9270, HIP 7097, HR 437, SAO 92484, WDS J01315+1521AB[9]
Database references
SIMBADdata

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 /ˈælfɜːrɡ/, the traditional name of the system)[10] and B.

  1. ^ a b c d e f Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Oja1985 was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Keenan1989 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Villaver2013 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Cvetkovic2010 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Auriere2015 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ "Naming Stars". IAU.org. Retrieved 18 June 2018.