27 Piscium

27 Piscium
Location of 27 Piscium (circled). It forms the apex of a narrow triangle sharing other stars of similar brightness, 30 (YY) and 33 Piscium.
Observation data
Epoch J2000      Equinox J2000
Constellation Pisces
Right ascension 23h 58m 40.37708s[1]
Declination −03° 33′ 21.5379″[1]
Apparent magnitude (V) 4.88[2] (4.90 + 8.90)[3]
Characteristics
Spectral type G8 III[4]
B−V color index 0.930[2]
Astrometry
Radial velocity (Rv)−0.20±0.07[5] km/s
Proper motion (μ) RA: −57.13[1] mas/yr
Dec.: −72.08[1] mas/yr
Parallax (π)13.91 ± 0.28 mas[1]
Distance234 ± 5 ly
(72 ± 1 pc)
Absolute magnitude (MV)0.60[2]
Orbit[6]
Period (P)695 yr
Semi-major axis (a)3.67″
Eccentricity (e)0.766
Inclination (i)81.0°
Longitude of the node (Ω)81.1°
Periastron epoch (T)2550.00
Argument of periastron (ω)
(secondary)		109.6°
Details[5]
55 Per A
Mass2.39±0.12 M☉
Radius9.73±0.51 R☉
Luminosity56+11
−9 L☉
Surface gravity (log g)2.82±0.07 cgs
Temperature5,014±23 K
Metallicity [Fe/H]0.03±0.05 dex
Rotational velocity (v sin i)1.29±0.56 km/s
Age710±120 Myr
Other designations
27 Psc, BD−04° 5996, FK5 900, HD 224533, HIP 118209, HR 9067, SAO 147008, WDS J23587-0333AB[7]
Database references
SIMBADdata

27 Piscium is a binary star system in the zodiac constellation of Pisces. It is visible to the naked eye with an apparent visual magnitude of 4.88.[2] Based upon an annual parallax shift of 13.91±0.28 mas,[1] it is located about 234 light years away. The system is positioned near the ecliptic and so is subject to occultation by the Moon.[8]

This star was found to be a double by American astronomer S. W. Burnham.[9][3] By 2002, sufficient position data had been gathered that orbital motion could be demonstrated, and preliminary elements were determined. The system has an orbital period of 695 years and an eccentricity of 0.766.[6] However, the orbital elements do not fully explain the radial velocity variations, which may indicate there is a brown dwarf companion.[10] This candidate object would have a mass of at least 73 MJ and is orbiting with a semimajor axis of around 4 AU.[11]

At the age of around 710 million years,[5] the primary, component A, is a first ascent giant star[12] on the red giant branch with a stellar classification of G8 III,[4] which means it is generating energy through hydrogen fusion along a shell surrounding an inert helium core. It has 2.4 times the mass of the Sun and has expanded to 10 times the Sun's radius. The star is radiating about 56 times the Sun's luminosity from its photosphere at an effective temperature of 5,014 K.[5]

In 2012, the magnitude 8.9 companion, component B, was at an angular separation of 0.80 arcseconds along a position angle of 325°.[3]

  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 Anderson2012 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference WDSC2014 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Houk1999 was invoked but never defined (see the help page).
  5. ^ a b c d Cite error: The named reference Jofre2015 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Seymour2002 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Brown1932 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Hartkopf2006 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Setiawan2004a was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Setiawan2004b was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Tautvaisiene2013 was invoked but never defined (see the help page).