Alpha Piscium

α Piscium
Location of α Piscium (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Pisces
Right ascension 02h 02m 02.81972s
Declination +02° 45′ 49.5410″
Apparent magnitude (V) 3.82 (4.33 + 5.23)
Characteristics
Evolutionary stage main sequence: 16 
Spectral type kA0hA7 Sr + kA2hF2mF2 (IV)
Variable type α2 CVn
Astrometry
Proper motion (μ) RA: +32.45 mas/yr
Dec.: +0.04 mas/yr
Parallax (π)20.76±0.15 mas
Distance157.1 ± 1.1 ly
(48.17±0.34 pc)
Absolute magnitude (MV)+0.50
Orbit
Primaryα Psc A
Secondaryα Psc B
Period (P)2,822±215 yr
Semi-major axis (a)7.45±0.35"
(359 AU)
Eccentricity (e)0.4650±0.0145
Inclination (i)113.01±2.45°
Longitude of the node (Ω)3.09±6.28°
Periastron epoch (T)2188.6
Argument of periastron (ω)
(secondary)		150±6°
Orbit
Primaryα Psc Ba
Secondaryα Psc Bb
Period (P)24.999428±0.000033 days
Semi-major axis (a)(5.175±0.018)×10−3"
(0.2493±0.0020 AU)
Eccentricity (e)0.6004±0.0018
Inclination (i)65.2±0.4°
Longitude of the node (Ω)73.08±0.63°
Argument of periastron (ω)
(primary)		140.14±0.42°
Semi-amplitude (K1)
(primary)		61.17±0.35 km/s
Semi-amplitude (K2)
(secondary)		61.97±0.47 km/s
Details
α Psc A
Mass2.49±0.05 M☉
Radius2.33±0.26 R☉
Luminosity53.7+8.0
−6.9 L☉
Surface gravity (log g)4.01±0.14 cgs
Temperature10,000±710 K
Rotation1.491±0.022 days
Rotational velocity (v sin i)81 km/s
Age330±150 Myr
α Psc Ba
Mass1.668±0.033 M☉
Radius1.76±0.41 R☉
Surface gravity (log g)4.0 cgs
Temperature8,000 K
α Psc Bb
Mass1.646±0.029 M☉
Radius1.55±0.41 R☉
Surface gravity (log g)4.0 cgs
Temperature8,000 K
Other designations
Alrischa, Kaitain, Okda, Okdah, Syndesmos, α Psc, 113 Piscium, BD+02°317, FK5 28, HIP 9487, SAO 110291, WDS J02020+0246AB
α Psc A: HD 12447, HR 596
α Psc B: HD 12446, HR 595
Database references
SIMBADα Psc
α Psc A
α Psc B

Alpha Piscium (α Piscium) is a triple star system in the equatorial constellation of Pisces. Based upon dynamical parallax measurements, it is about 157 light-years from the Solar System.

The three components are designated Alpha Piscium A (officially named Alrescha /ælˈriːʃə/, the traditional name of the system), Ba and Bb.

Nomenclature

α Piscium (Latinised to Alpha Piscium) is the star's Bayer designation. The designations of the two components as Alpha 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).

The system bore the traditional name Alrescha (alternatively Al Rescha, Alrischa, Alrisha) derived from the Arabic الرشآء ar-Rishā’ "the cord" and less commonly Kaitain and Okda, the latter from the Arabic عقدة ʽuqdah "knot" (see Ukdah). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name Alrescha for the component Alpha Piscium A on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.

In Chinese, 外屏 (Wài Píng), meaning Outer Fence, refers to an asterism consisting of Alpha Piscium, Delta Piscium, Epsilon Piscium, Zeta Piscium, Mu Piscium, Nu Piscium and Xi Piscium. Consequently, the Chinese name for Alpha Piscium itself is 外屏七 (Wài Píng qī, English: the Seventh Star of Outer Fence).

Properties

Alpha Piscium comprises an hierarchical architecture. The outer system comprises the star Alpha Piscium A and the subsystem Alpha Piscium B, separated by 1.85". Alpha Piscium A, the primary, is of magnitude +4.33 and spectral type kA0hA7 Sr, while the components of Alpha Piscium B have combined magnitude 5.23 and combined spectral class kA2hF2mF2 (IV). The two bodies take roughly 2,800 years to orbit one another and they will make their closest approach to each other around 2188. The components of Alpha Piscium B, called Ba and Bb, have an orbital period of roughly 25 days and a semi-major axis of 0.2493±0.0020 AU.

A light curve for Alpha Piscium, plotted from TESS data

Alpha Piscium is catalogued as an α2 Canum Venaticorum variable, a type of variable star where the brightness changes are caused by the rotation of the star. The brightness varies by about 1/100 of a magnitude, identified from Hipparcos photometry. The primary component is thought to be the source of the variations, and it has a period of 0.845 days which was believed to be the rotation period of the star, but the latter has been revised to 1.49 days. Variations with a period of 6.65 days have also been identified.

Alpha Piscium composes a four-star system together with the G1/2V star HIP 9519, which is separated by 404.7".

Long-exposure observation

Stars that can set (not in a circumpolar constellation for the viewer) culminate at midnight – where viewed away from any polar region experiencing midnight sun – when at opposition, meaning they can be viewed from dusk until dawn. This applies to α Piscium on 21 October, in the current astronomical epoch.

Half of the year from this date, 22 April, the star will be at conjunction above or below, the sun – apart by the star's declination (angle set out in table, right). The nearby days and months have most of the star's risen time during daylight.[citation needed]

Notes

  1. ↑ Semi-major axis in AU = = 359 AU; as the eccentricity is 0.465, the distance fluctuates between 53.5% and 146.5% of that, roughly from 192 AU to 526 AU.

References

  1. 1 2 3 4 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
  2. 1 2 3 Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
  3. 1 2 3 4 Sikora, J.; Wade, G. A.; Power, J.; Neiner, C. (2019), "A volume-limited survey of MCP stars within 100 pc - I. Fundamental parameters and chemical abundances", Monthly Notices of the Royal Astronomical Society, 483 (2): 2300, arXiv:1811.05633, Bibcode:2019MNRAS.483.2300S, doi:10.1093/mnras/sty3105, S2CID 119089236.
  4. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Anugu, Narsireddy; Klement, Robert; Monnier, John D.; Gies, Douglas R.; Schaefer, Gail H.; Kraus, Stefan; Carrazco-Gaxiola, Sebastián; Chaturvedi, Akshat S.; Gutierrez, Mayra (2026-03-10), "Detection and Astrometry of the Ba-Bb Subsystem in α Piscium: First Dual-Field Interferometry at the CHARA Array", The Astronomical Journal, arXiv:2603.09489.
  5. 1 2 3 Gray, R. O.; Garrison, R. F. (July 1989), "The Late A-Type Stars: Refined MK Classification, Confrontation with Stroemgren Photometry, and the Effects of Rotation", Astrophysical Journal Supplement, 70: 623, Bibcode:1989ApJS...70..623G, doi:10.1086/191349.
  6. 1 2 Samus, N. N.; Durlevich, O. V.; et al. (2009), "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)", VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S, 1: B/GCVS, Bibcode:2009yCat....102025S.
  7. ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  8. 1 2 Hartkopf, W. I.; et al. (June 30, 2006), Sixth Catalog of Orbits of Visual Binary Stars, United States Naval Observatory, archived from the original on 2017-08-01, retrieved 2017-06-02.
  9. 1 2 Shultz, M E; Owocki, S P; ud-Doula, A; Biswas, A; Bohlender, D; Chandra, P; Das, B; David-Uraz, A; Khalack, V; Kochukhov, O; Landstreet, J D; Leto, P; Monin, D; Neiner, C; Rivinius, Th (2022-04-29), "MOBSTER – VI. The crucial influence of rotation on the radio magnetospheres of hot stars", Monthly Notices of the Royal Astronomical Society, 513 (1): 1429–1448, arXiv:2201.05512, doi:10.1093/mnras/stac136, ISSN 0035-8711.
  10. ↑ Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393: 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943, S2CID 14070763.
  11. ↑ "alf Psc", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2017-08-04.
  12. ↑ Peterson, Hannah Mary Bouvier (1856). Familiar Astronomy, Or, An Introduction to the Study of the Heavens. London: Princeton University. p. 434.
  13. ↑ "alf Psc A", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2017-08-04.
  14. ↑ "alf Psc B", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2017-08-04.
  15. ↑ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  16. 1 2 "Naming Stars". IAU.org. Retrieved 2 March 2018.
  17. ↑ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  18. ↑ Allen, Richard Hinckley (1899), Star-names and their meanings, G. E. Stechert, pp. 342−343.
  19. ↑ Division C WG Star Names, IAU Working Group on Star Names (WGSN), retrieved 22 May 2016.
  20. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 19 日 Archived 2016-03-03 at the Wayback Machine
  21. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
  22. 1 2 Wraight, K. T.; Fossati, L.; Netopil, M.; Paunzen, E.; Rode-Paunzen, M.; Bewsher, D.; Norton, A. J.; White, Glenn J. (2012). "A photometric study of chemically peculiar stars with the STEREO satellites - I. Magnetic chemically peculiar stars". Monthly Notices of the Royal Astronomical Society. 420 (1): 757. arXiv:1110.6283. Bibcode:2012MNRAS.420..757W. doi:10.1111/j.1365-2966.2011.20090.x. S2CID 14811051.
  23. ↑ Ephemera table, rising and setting times In-the-Sky.org. Dominic C. Ford, 2011–2020; Cambridge UK.