Mu2 Scorpii

Mu2 Scorpii (μ2 Scorpii, abbreviated Mu2 Sco, μ2 Sco), also named Pipirima /pɪˈpɪrɪmə/,[11] is a star in the zodiac constellation of Scorpius. It has an apparent visual magnitude of +3.56,[2] which is bright enough to be seen with the naked eye. Its distance from the Sun is about 474 light-years, as determined by parallax measurements.[1] It is a member of the Upper Centaurus–Lupus subgroup of the Scorpius–Centaurus association.[12]

For other star systems with a similar Bayer designation, see Mu Scorpii.
μ2 Scorpii
(Pipirima)
Location of μ2 Scorpii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius
Right ascension 16h 52m 20.14532s[1]
Declination −38° 01′ 03.1258″[1]
Apparent magnitude (V) +3.56[2]
Characteristics
Spectral type B2 IV[3]
U−B color index −0.878[2]
B−V color index −0.219[2]
Astrometry
Radial velocity (Rv)+1.4[4] km/s
Proper motion (μ) RA: −11.09[1] mas/yr
Dec.: −23.32[1] mas/yr
Parallax (π)6.88 ± 0.12 mas[1]
Distance474 ± 8 ly
(145 ± 3 pc)
Absolute magnitude (MV)−2.25[5]
Details
Mass8.7±0.2[6] M☉
Radius7.0[7] R☉
Luminosity2,385[8] L☉
Temperature23,113[7] K
Rotational velocity (v sin i)58[9] km/s
Age18.5±3.2[6] Myr
Other designations
Pipirima, μ2 Scorpii, CD−37° 11037, HD 151985, HIP 82545, HR 6252, SAO 208116.[10]
Database references
SIMBADdata

Properties

This is a blue-white, B-type subgiant star with a stellar classification of B2 IV.[3] It has an estimated 7 times the radius of the Sun, almost 9 times the Sun's mass,[6] and shines with 2,385 times the Sun's luminosity.[8] The outer atmosphere has an effective temperature of 23,113 K.[7] It is some 18.5[6] million years old and is spinning with a projected rotational velocity of 58 km/s.[9]

Nomenclature

μ2 Scorpii (Latinised to Mu2 Scorpii) is the star's Bayer designation.

In Tahiti, a traditional story is told of a brother and sister, named Pipiri and Rehua, who flee their parents into the sky and become stars. Their parents call them Pipiri ma while chasing them into the sky: ma "with, and" is used after names to mean "et al."[13][14] In one account, the children become Shaula and Lesath in the tip of the tail of Scorpio,[13] and in another they become Mu2 and Mu1 Scorpii. (In a similar version of the story told in the Cook Islands, they become Omega1 and Omega2 Scorpii).[13]

In 2016, the IAU organized a Working Group on Star Names (WGSN)[15] to catalog and standardize proper names for stars. The WGSN approved the name Pipirima for this star on 5 September 2017 (along with Xamidimura for its partner) and it is now so included in the List of IAU-approved Star Names.[11]

In Chinese astronomy, Mu2 Scorpii is called 尾宿增二.[16]

Planetary system

Two sub-stellar objects slightly above deuterium burning limit (brown dwarfs) were found in 2022 by direct imaging near Mu2 Scorpii. The outer one, designated μ2 Scorpii b, is definitely an orbiting planet or brown dwarf, and the inner one is a planetary candidate.[17]

The Mu2 Scorpii planetary system[17]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(years)		 Eccentricity Inclination Radius
c (unconfirmed) 18.5±1.5 MJ 18.9+11.7
−5.0		 — 0.61+0.19
−0.32		 62.8+9.9
−16.6°		 —
b 14.4±0.8 MJ 242.4+114.5
−52.1		 — 0.56+0.27
−0.26		 96.6+21.5
−20.5°		 —

References
  1. van 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.
  2. Gutierrez-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.
  3. Hiltner, W. A.; et al. (July 1969), "MK Spectral Types for Bright Southern OB Stars", The Astrophysical Journal, 157: 313, Bibcode:1969ApJ...157..313H, doi:10.1086/150069.
  4. Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick (eds.), "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, vol. 30, p. 57, Bibcode:1967IAUS...30...57E.
  5. 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.
  6. Tetzlaff, N.; et al. (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.
  7. Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189 (3): 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601.
  8. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
  9. Uesugi, Akira; Fukuda, Ichiro (1970), "Catalogue of rotational velocities of the stars", Contributions from the Institute of Astrophysics and Kwasan Observatory, University of Kyoto, Bibcode:1970crvs.book.....U.
  10. "mu.02 Sco". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-09-20.{{cite web}}: CS1 maint: postscript (link)
  11. "Naming Stars". IAU.org. Retrieved 16 December 2017.
  12. Bobylev, V. V.; Bajkova, A. T. (September 2007), "Kinematics of the Scorpius–Centaurus OB association", Astronomy Letters, 33 (9): 571–583, arXiv:0708.0943, Bibcode:2007AstL...33..571B, doi:10.1134/S1063773707090010, S2CID 15785349.
  13. Johannes Carl Andersen (1931) Myths and Legends of the Polynesians. 1995 Dover reprint, p.400ff.
  14. Herbert John Davies, A Tahitian and English dictionary, with introductory remarks on the Polynesian language, and a short grammar of the Tahitian dialect. London Missionary Society, 1851.
  15. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  16. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 10 日
  17. Squicciarini, V.; Gratton, R.; Janson, M.; Mamajek, E. E.; Chauvin, G.; Delorme, P.; Langlois, M.; Vigan, A.; Ringqvist, S. C.; Meeus, G.; Reffert, S.; Kenworthy, M.; Meyer, M. R.; Bonnefoy, M.; Bonavita, M.; Mesa, D.; Samland, M.; Desidera, S.; d'Orazi, V.; Engler, N.; Alecian, E.; Miglio, A.; Henning, T.; Quanz, S. P.; Mayer, L.; Flasseur, O.; Marleau, G.-D. (2022), "A scaled-up planetary system around a supernova progenitor", Astronomy & Astrophysics, 664: A9, arXiv:2205.02279, doi:10.1051/0004-6361/202243675, S2CID 248524983
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