WR 104

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WR 104
Observation data
Epoch 2000      Equinox 2000
Constellation Sagittarius
Right ascension 18h 02m 04.07s[1]
Declination −23° 37′ 41.2″[1]
Apparent magnitude (V) 13.28[2]
Spectral type WC9d/B0.5V[3]
Distance 1,670[4] - 2,300[3] pc
Absolute magnitude (MV) −4.8 - −6.6 + −5.94 - −6.11[4]
Mass 14.9 + 35.9[4] M
Radius ~8[5] R
Luminosity ~150,000[5] L
Temperature 40,000[5] K
Other designations
V5097 Sgr, IRAS 17590-2337, UCAC2 22296214, CSI-23-17590, IRC −20417, RAFGL 2048, MSX6C G006.4432-00.4858
Database references

Coordinates: Sky map 18h 02m 04.07s, −23° 37′ 41.2″

WR 104 is a binary star system located 5,000-7,500 light years from Earth. The primary star is a Wolf-Rayet star and the secondary is an OB star.

WR 104 is surrounded by a distinctive dusty pinwheel nebula over 200 astronomical units long formed by interaction between the stellar winds of the two stars as they rotate and orbit. The spiral is composed of dust that would normally be prevented from forming by WR 104's intense radiation were it not for the star's companion. The region where the stellar wind from the two massive stars interacts compresses the material enough for the dust to form, and the rotation of the system causes the spiral-shaped pattern.[6]

By convention, the Wolf-Rayet star is considered to be the primary although it is less massive and less visually bright than the secondary. Its very high temperature means that it dominates the total luminosity of the system and its prominent emission lines dominate the spectrum. The round appearance of the spiral led to the assumption that the system was seen almost pole on, and an almost circular orbital period of 220 days had been assumed from the pinwheel outflow pattern.[7] However, direct observations of the orbit show an eccentric orbit (e = 0.8964) with a period of 2,896 days and an inclination of 119.6°.[4]

WR 104 shows frequent eclipse events as well as other irregular variations in brightness. The undisturbed apparent magnitude is around 12.7, but the star is rarely at that level. The eclipses are believed to be by dust formed from expelled material, not by the companion star.[2]


  1. ^ a b . Bibcode:2003yCat.2246....0C.  Missing or empty |title= (help)
  2. ^ a b . doi:10.1093/mnras/stu1779.  Missing or empty |title= (help)
  3. ^ a b Van Der Hucht, K. A. (2001). "The VIIth catalogue of galactic Wolf–Rayet stars". New Astronomy Reviews 45 (3): 135. doi:10.1016/S1387-6473(00)00112-3.  edit
  4. ^ a b c d . doi:10.1088/2041-8205/742/1/L1.  Missing or empty |title= (help)
  5. ^ a b c Sander, A.; Hamann, W. -R.; Todt, H. (2012). "The Galactic WC stars". Astronomy & Astrophysics 540: A144. arXiv:1201.6354. Bibcode:2012A&A...540A.144S. doi:10.1051/0004-6361/201117830.  edit
  6. ^ Tuthill, P. G.; Monnier, J. D.; Danchi, W. C. (1999). "A dusty pinwheel nebula around the massive star WR104". Nature 398 (6727): 487. Bibcode:1999Natur.398..487T. doi:10.1038/19033.  edit
  7. ^ Tuthill, P. G.; Monnier, J. D.; Lawrance, N.; Danchi, W. C.; Owocki, S. P.; Gayley, K. G. (2008). "The Prototype Colliding‐Wind Pinwheel WR 104". The Astrophysical Journal 675: 698. doi:10.1086/527286.  edit

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