Mu2 Scorpii

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μ² Scorpii
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]
Spectral type B2 IV[3]
U−B color index −0.878[2]
B−V color index −0.219[2]
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[1] mas
Distance474 ± 8 ly
(145 ± 3 pc)
Absolute magnitude (MV)−2.25[5]
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

Mu² Scorpii (μ² Scorpii, abbreviated Mu² Sco, μ² Sco), also named Pipirima,[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]


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

It bore the traditional name Pipirima in Polynesian mythology. Especially in Tahitian myths, Pipirima is one of the 'Piri-ere-ua' (meaning 'The Inseparable Ones'), two children, a boy (named Pipirima) and a girl (named Réhua), who were fleeing their wicked parents and then became stars in the sky. According to other sources the boy's name is Pipiri and Pipiri-ma refers to 'Pipiri and his sister'.[13][14][15][16] In 2016, the IAU organized a Working Group on Star Names (WGSN)[17] to catalog and standardize proper names for stars. The WGSN approved the name Pipirima for this star on 5 September 2017 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.[18]


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]


  1. ^ a b c d e f 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.
  2. ^ a b c d 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. ^ a b 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, 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.
  6. ^ a b c d 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: 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x.
  7. ^ a b c 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: 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601.
  8. ^ a b 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.
  9. ^ a b Uesugi, Akira; Fukuda, Ichiro (1970), "Catalogue of rotational velocities of the stars", Contributions from the Institute of Astrophysics and Kwasan Observatory, University of Kyoto,
  10. ^ "mu.02 Sco". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-09-20.
  11. ^ a b "Naming Stars". 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.
  13. ^ Robert Burnham (1978). Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System. Courier Corporation. p. 1680. ISBN 978-0-486-23673-5.
  14. ^ [1], on: fnac (french)
  15. ^ Légende de Pipiri-ma, on: Tahiti Heritage
  16. ^ "IAU Approves 86 New Star Names From Around the World" (Press release). 11 December 2017.
  17. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  18. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 10 日

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