It consists of a binary pair, designated Pi Scorpii A, with a more distant third companion, B. A's two components are themselves designated Pi Scorpii Aa (formally named Fang)[11] and Ab.
Nomenclature
π Scorpii (Latinised to Pi Scorpii) is the system's Bayer designation. The designations of the three constituents as Pi Scorpii A and B and those of A's components - Pi Scorpii Aa and Ab - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[12]
In Chinese, 房宿 (Fáng Xiù), meaning Room, refers to an asterism consisting of Pi Scorpii, Rho Scorpii, Delta Scorpii, Beta¹ Scorpii and Beta² Scorpii.[13] Consequently, the Chinese name for Pi Scorpii itself is 房宿一 (Fáng Xiù yī), "the First Star of Room".[14] In 2016, the IAU organized a Working Group on Star Names (WGSN)[15] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[16] It approved the name Fang for the component Pi Scorpii Aa on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.[11]
The primary, or A, component of this system itself forms an eclipsing binary of the Beta Lyrae type.[17] Both its members are hot, B-typemain sequence stars with a blue-white hue. They display an ellipsoidal variation of 0.03 in magnitude.[7] The two stars are rotating rapidly, with projected rotational velocities of 108 and 87 km/s respectively.[6] Their orbital period is 1.57 days and they are separated by an estimated distance of only 15 solar radii along a circular orbit.[6]
The primary is orbited by a smaller, more distant companion (B), which has an apparent magnitude of +12.2. This component is separated from the pair by 50 arcseconds, putting it at least 7000 AU away.[citation needed]
The Pi Scorpii system is a kinematic member of the Upper Scorpius subgroup of the Scorpius–Centaurus association, a group of thousands of young stars with mean age 11 million years at distance 470 light years (145 parsecs).[9] A recent analysis[9] of the HR diagram position for the primary star Pi Scorpii A estimates its effective temperature to be 25,230 kelvins with a luminosity of 21,900 Suns, consistent with an isochronal age of 12-14 million years and an estimated mass of 12–13 solar masses.
References
^ a b c d evan Leeuwen, F. (November 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
^ a b c d eGutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement, 15: 459, Bibcode:1968ApJS...15..459G, doi:10.1086/190168
^Houk, Nancy; Smith-Moore, M. (1979), "Michigan catalogue of two-dimensional spectral types for the HD stars", Ann Arbor: Dept. Of Astronomy, 1, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H
^Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick (eds.), Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, vol. 30, University of Toronto: International Astronomical Union, p. 57, Bibcode:1967IAUS...30...57E
^ a b c d e f g hStickland, D. J.; et al. (December 1996), "Spectroscopic binary orbits from ultraviolet radial velocities Paper 23: Pi Scorpii (HD 143018)", The Observatory, 116: 387–391, Bibcode:1996Obs...116..387S
^ a b cShobbrook, R. R. (December 2005), "Photometry of 20 eclipsing and ellipsoidal binary systems", The Journal of Astronomical Data, 11: 7, Bibcode:2005JAD....11....7S
^ a bTetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873
^ a b c d e fMark J. Pecaut; Eric E. Mamajek & Eric J. Bubar (February 2012). "A Revised Age for Upper Scorpius and the Star Formation History among the F-type Members of the Scorpius–Centaurus OB Association". Astrophysical Journal. 746 (2): 154. arXiv:1112.1695. Bibcode:2012ApJ...746..154P. doi:10.1088/0004-637X/746/2/154. S2CID 118461108.
^Kaler, James B., "PI SCO (Pi Scorpii)", Stars, University of Illinois, retrieved 2012-01-14
^ a b"Naming Stars". IAU.org. Retrieved 16 December 2017.
^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].
^(in Chinese)中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
^(in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
^"IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
^"WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
^"pi. Sco -- Eclipsing binary of beta Lyr type", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-14