Pi Puppis

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Pi Puppis
Diagram showing star positions and boundaries of the Puppis constellation and its surroundings
Cercle rouge 100%.svg
Location of π Puppis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Puppis
Right ascension 07h 17m 08.55678s[1]
Declination −37° 05′ 50.8962″[1]
Apparent magnitude (V) 2.733[2]
Spectral type K3 Ib[3]
U−B color index +1.238[2]
B−V color index +1.608[2]
Variable type SRd[4]
Radial velocity (Rv)+15.8[5] km/s
Proper motion (μ) RA: −10.05[1] mas/yr
Dec.: +6.47[1] mas/yr
Parallax (π)4.04 ± 0.33[1] mas
Distance810 ± 70 ly
(250 ± 20 pc)
Absolute magnitude (MV)4.5[6]
Mass11.7 ± 0.2[7] M
Radius290[8][better source needed] R
Diameter290[8][better source needed] D
Luminosity11,825[9] L
Temperature3,990–4,055[10] K
Age20.0 ± 3.9[7] Myr
Other designations
π Pup, CPD−36° 1211, FK5 278, GC 9706, PPM=283747, HD 56855, HIP 35264, HR 2773, SAO 197795, CCDM J07171-3706A, WDS J07171-3706Aa,Ab[11]
Database references

Pi Puppis, Latinized from π Puppis, also named Ahadi,[12][13] is the second-brightest star in the southern constellation of Puppis. It has an apparent visual magnitude of 2.733,[2] so it can be viewed with the naked eye at night. Parallax measurements yield an estimated distance of roughly 810 light-years (250 parsecs) from the Earth.[1] This is a double star with a magnitude 6.86 companion at an angular separation of 0.72 arcsecond and a position angle of 148° from the brighter primary.[14]

The spectrum of Pi Puppis matches a stellar classification of K3 Ib.[3] The Ib luminosity class indicates this a lower luminosity supergiant star that has consumed the hydrogen fuel at its core, evolved away from the main sequence, and expanded to about 290 times the Sun's radius.[8] The effective temperature of the star's outer envelope is approximately 4,000 K,[10] which gives it the orange hue of a K-type star.[15] It is a semiregular variable star[4] that varies in apparent magnitude from a high of 2.70 down to 2.85.[16] Pi Puppis is the brightest star in the open cluster Collinder 135.[17]


The star has the traditional name Ahadi, which is derived from Arabic for "having much promise".[12] In Chinese, 弧矢 (Hú Shǐ), meaning Bow and Arrow,[18] refers to an asterism consisting of π Puppis, δ Canis Majoris, η Canis Majoris, HD 63032, HD 65456, ο Puppis, k Puppis, ε Canis Majoris and κ Canis Majoris. Consequently, π Puppis itself is known as 弧矢九 (Hú Shǐ jiǔ, English: the Ninth Star of Bow and Arrow.)[19]


  1. 1.0 1.1 1.2 1.3 1.4 1.5 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. 2.0 2.1 2.2 2.3 Gutierrez-Moreno, Adelina et al. (1966), "A System of photometric standards", Publ. Dept. Astron. Univ. Chile (Publicaciones Universidad de Chile, Department de Astronomy) 1: 1–17, Bibcode 1966PDAUC...1....1G
  3. 3.0 3.1 Houk, Nancy (1979), "Michigan catalogue of two-dimensional spectral types for the HD stars", Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Volume_3. Declinations -40_ƒ0 to -26_ƒ0 (Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan) 3, Bibcode 1982mcts.book.....H
  4. 4.0 4.1 Kazarovets, E. V. et al. (January 1999), "The 74th Special Name-list of Variable Stars", Information Bulletin on Variable Stars 4659: 1, Bibcode 1999IBVS.4659....1K
  5. Lua error in Module:Citation/CS1 at line 637: attempt to concatenate local 'chapter' (a table value).
  6. Parsons, Sidney B. (2001). "A Large Spectral Class Dependence of the Wilson-Bappu Effect among Luminous Stars". The Publications of the Astronomical Society of the Pacific 113 (780): 188. Bibcode 2001PASP..113..188P. doi:10.1086/318616.
  7. 7.0 7.1 Tetzlaff, 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
  8. 8.0 8.1 Kaler, james B., "PI PUP (Pi Puppis)", Stars (University of Illinois), http://stars.astro.illinois.edu/sow/pipup.html, retrieved 2012-01-10
  9. 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.
  10. 10.0 10.1 Pérez Martínez, M. Isabel; Schröder, K.-P.; Cuntz, M. (June 2011), "The basal chromospheric Mg II h+k flux of evolved stars: probing the energy dissipation of giant chromospheres", Monthly Notices of the Royal Astronomical Society 414 (1): 418–427, arXiv:1102.4832, Bibcode 2011MNRAS.414..418P, doi:10.1111/j.1365-2966.2011.18421.x
  11. "CCDM J07171-3706A -- Double or multiple star", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Pi+Puppis
  12. 12.0 12.1 Poppele, Jonathan (2010), Night Sky: A Field Guide to the Constellations, Adventure Publications, p. 264, ISBN 1591932297, https://books.google.com/books?id=LbAbDQAAQBAJ&pg=PA264.
  13. http://server7.sky-map.org/starview?object_type=1&object_id=317&locale=EN
  14. Fabricius, C.; Makarov, V. V. (April 2000), "Two-colour photometry for 9473 components of close Hipparcos double and multiple stars", Astronomy and Astrophysics 356: 141–145, Bibcode 2000A&A...356..141F
  15. "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html, retrieved 2012-01-16
  16. Burnham, Robert (1978), Burnham's celestial handbook: an observer's guide to the universe beyond the solar system, Dover books explaining science, 3 (2nd ed.), Courier Dover Publications, p. 1499, ISBN 0-486-23673-0, https://books.google.com/books?id=PJzIt3SIlkUC&pg=PA1499
  17. Eggen, O. J. (February 1983), "Six clusters in Puppis-Vela", Astronomical Journal 88: 197–214, Bibcode 1983AJ.....88..197E, doi:10.1086/113306
  18. 弧矢 (Hú Shǐ) is westernized into Koo She. R.H. Allen had opinion that Koo She refers to the asterism including δ Velorum and ω Velorum. AEEA opinion is, δ Velorum is member of 天社 (Tiān Shè), meaning Celestial Earth God's Temple asterism and ω Velorum is not member of any asterisms. 天社 (Tiān Shè)is westernized into Tseen She and R.H.Allen used the term Tseen She for Chinese name of η Carinae. See Richard Hinckley Allen: Star Names — Their Lore and Meaning: Argo Navis and (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 17 日.
  19. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 16 日

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