Phi Sagittarii

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Phi Sagittarii
Diagram showing star positions and boundaries of the Sagittarius constellation and its surroundings
Cercle rouge 100%.svg

Location of φ Sagittarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 18h 45m 39.38610s[1]
Declination –26° 59′ 26.7944″[1]
Apparent magnitude (V) 3.17[2]
Characteristics
Spectral type B8.5 III[3] to B7 IV[4]
U−B color index –0.36[5]
B−V color index –0.11[5]
Astrometry
Radial velocity (Rv) +21.5[2] km/s
Proper motion (μ) RA: +50.61[1] mas/yr
Dec.: +1.22[1] mas/yr
Parallax (π) 13.63 ± 0.19[1] mas
Distance 239 ± 3 ly
(73 ± 1 pc)
Details
Mass 4–4.2[6] M
Radius 4.8[6] R
Luminosity 475[6] L
Temperature 14,990[4] K
Rotational velocity (v sin i) 35[7] km/s
Age 1.65 × 108[6] years
Other designations
φ Sagittarii, φ Sgr, Phi Sgr, 27 Sagittarii, 27 Sagittarii, CPD-27  5241, FK5 1487, GC 25661, HD 173300, HIP 92041, HR 7039, PPM 297231, SAO 268859.[8]

Phi Sagittarii (Phi Sgr, φ Sagittarii, φ Sgr) is a star in the southern constellation of Sagittarius. With an apparent visual magnitude of 3.17,[2] it is the ninth brightest star in the constellation and is readily visible to the naked eye. Parallax measurements place it at a distance of roughly 239 light-years (73 pc) from the Earth.[1]

The stellar classification of this star has been rated at B8.5 III[3] and B7 IV,[4] with a luminosity class of III indicating it is a giant star, while a class of IV suggests it is still a subgiant star. Both represent stages in the evolution of a star after it has exhausted the hydrogen at its core. This energy is being radiated from the star's outer envelope at an effective temperature of 14,990 K,[4] which produces the blue-white hue typical of B-type stars.[9]

In the past, this star catalogued as a spectroscopic binary and a companion was apparently detected through lunar occultation.[10] However, it is most likely a solitary star[6][11] and any nearby stars are merely optical companions.

Name and etymology[edit]

References[edit]

  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 Wielen, R. et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W 
  3. ^ a b Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars 3, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1982MSS...C03....0H 
  4. ^ a b c d Zorec, J. et al. (July 2009), "Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff", Astronomy and Astrophysics 501 (1): 297–320, Bibcode:2009A&A...501..297Z, doi:10.1051/0004-6361/200811147 
  5. ^ a b Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99), Bibcode:1966CoLPL...4...99J 
  6. ^ a b c d e Kaler, James B., "PHI SGR (Phi Sagittarii)", Stars (University of Illinois), retrieved 2012-01-15 
  7. ^ Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590 
  8. ^ "phi Sgr -- Star", SIMBAD (Centre de Données astronomiques de Strasbourg), retrieved 2012-01-15 
  9. ^ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16 
  10. ^ Finsen, W. S. (April 1951), "The duplicity of phi Sgr", Astronomical Journal 56: 56, Bibcode:1951AJ.....56Q..56F, doi:10.1086/106589 
  11. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x 
  12. ^ "Sagittarius". deepsky.astroinfo.org. Retrieved 30 August 2008. 
  13. ^ skywatchers[dead link]
  14. ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 355. ISBN 0-486-21079-0. Retrieved 2012-09-04. 
  15. ^ Jack W. Rhoads - Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology; November 15, 1971
  16. ^ Knobel, E. B. (June 1895). "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket". Monthly Notices of the Royal Astronomical Society 55: 430. Bibcode:1895MNRAS..55..429K. 
  17. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 11 日