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Cygnus X-1

For other uses, see Cygnus X-1 (disambiguation).

Cygnus X-1
Location of Cygnus X-1 (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 19h 58m 21.67574s[1]
Declination +35° 12′ 05.7845″[1]
Apparent magnitude (V) 8.95[2]
Characteristics
Spectral type O9.7Iab[2]
U−B color index −0.30[3]
B−V color index +0.81[3]
Variable type Ellipsoidal variable
Astrometry
Radial velocity (Rv)−2.70±3.2[2] km/s
Proper motion (μ) RA: −3.812±0.015 mas/yr[1]
Dec.: −6.310±0.017 mas/yr[1]
Parallax (π)0.4439 ± 0.0149 mas[1]
Distance7,300 ± 200 ly
(2,250 ± 80 pc)
Absolute magnitude (MV)−6.5±0.2[4]
Details
Cygnus X-1
Mass21.2[5][6] M☉
Details
HDE 226868
Mass20–40 M☉
Radius20–22[7] R☉
Luminosity3–4×105[7] L☉
Surface gravity (log g)3.31±0.07[8] cgs
Temperature31000[9] K
Rotationevery 5.6 days
Age5[10] Myr
Other designations
AG (or AGK2)+35 1910, BD+34 3815, HD (or HDE) 226868, HIP 98298, SAO 69181, V1357 Cyg.[2]
Database references
SIMBADdata

Cygnus X-1 (abbreviated Cyg X-1)[11] is a galactic X-ray source in the constellation Cygnus and was the first such source widely accepted to be a black hole.[12][13] It was discovered in 1965 during a rocket flight and is one of the strongest X-ray sources detectable from Earth, producing a peak X-ray flux density of 2.3×10−23 W/(m2⋅Hz) (2.3×103 jansky).[14][15] It remains among the most studied astronomical objects in its class. The compact object is now estimated to have a mass about 21.2 times the mass of the Sun[5][6] and has been shown to be too small to be any known kind of normal star or other likely object besides a black hole.[16] If so, the radius of its event horizon has 300 km "as upper bound to the linear dimension of the source region" of occasional X-ray bursts lasting only for about 1 ms.[17]

Cygnus X-1 belongs to a high-mass X-ray binary system, located about 2.22 kiloparsecs from the Sun,[18] that includes a blue supergiant variable star designated HDE 226868,[19] which it orbits at about 0.2 AU, or 20% of the distance from Earth to the Sun. A stellar wind from the star provides material for an accretion disk around the X-ray source.[20] Matter in the inner disk is heated to millions of degrees, generating the observed X-rays.[21][22] A pair of relativistic jets, arranged perpendicularly to the disk, are carrying part of the energy of the infalling material away into interstellar space.[23]

This system may belong to a stellar association called Cygnus OB3, which would mean that Cygnus X-1 is about 5 million years old and formed from a progenitor star that had more than 40 solar masses. The majority of the star's mass was shed, most likely as a stellar wind. If this star had then exploded as a supernova, the resulting force would most likely have ejected the remnant from the system. Hence the star may have instead collapsed directly into a black hole.[10]

Cygnus X-1 was the subject of a friendly scientific wager between physicists Stephen Hawking and Kip Thorne in 1975, with Hawking—betting that it was not a black hole—hoping to lose.[24] Hawking conceded the bet in 1990 after observational data had strengthened the case that there was indeed a black hole in the system. As of 2004, this hypothesis lacked direct empirical evidence but was generally accepted based on indirect evidence.[25]

  1. ^ a b c d Cite error: The named reference GaiaDR3 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference lob647 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference apj321 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference SCI-20210218 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference NYT-20210218 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference MNRAS358_3_851 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference hadrava was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference eas030610 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference science300_5622_1119 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference science3656 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference esa20041105 was invoked but never defined (see the help page).
  13. ^ Glister, Paul (2011), "Cygnus X-1: A Black Hole Confirmed." Centauri Dreams: Imagining and Planning Interstellar Exploration, 2011-11-29. Accessed 2016-09-16.
  14. ^ Cite error: The named reference lewin_vanderklis2006 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference usno2010 was invoked but never defined (see the help page).
  16. ^ The Illustrated Encyclopedia of the Universe. New York, NY: Watson-Guptill. 2001. p. 175. ISBN 0-8230-2512-8.
  17. ^ Cite error: The named reference harko20060628 was invoked but never defined (see the help page).
  18. ^ Miller-Jones, James C. A.; Bahramian, Arash; Orosz, Jerome A.; Mandel, Ilya; Gou, Lijun; Maccarone, Thomas J.; Neijssel, Coenraad J.; Zhao, Xueshan; Ziółkowski, Janusz; Reid, Mark J.; Uttley, Phil; Zheng, Xueying; Byun, Do-Young; Dodson, Richard; Grinberg, Victoria; Jung, Taehyun; Kim, Jeong-Sook; Marcote, Benito; Markoff, Sera; Rioja, María J.; Rushton, Anthony P.; Russell, David M.; Sivakoff, Gregory R.; Tetarenko, Alexandra J.; Tudose, Valeriu; Wilms, Joern (5 March 2021). "Cygnus X-1 contains a 21–solar mass black hole—Implications for massive star winds". Science. 371 (6533): 1046–1049. arXiv:2102.09091. Bibcode:2021Sci...371.1046M. doi:10.1126/science.abb3363. PMID 33602863. S2CID 231951746.
  19. ^ Ziolkowski, Janusz (2014). "Masses of the components of the HDE 226868/Cyg X-1 binary system". Monthly Notices of the Royal Astronomical Society: Letters. 440: L61. arXiv:1401.1035. Bibcode:2014MNRAS.440L..61Z. doi:10.1093/mnrasl/slu002. S2CID 54841624.
  20. ^ Cite error: The named reference apj304_371 was invoked but never defined (see the help page).
  21. ^ Cite error: The named reference nayashin_dove1998 was invoked but never defined (see the help page).
  22. ^ Cite error: The named reference mnras325_3_1045 was invoked but never defined (see the help page).
  23. ^ Cite error: The named reference mdsai76_600 was invoked but never defined (see the help page).
  24. ^ "Inside Einstein's Mind". Nova. Season 42. Episode 23. 25 Nov 2015. Event occurs at 43:54. PBS. Kip Thorne: Stephen Hawking had a terribly deep investment in it actually being a black hole, and so he made the bet against himself as an insurance policy, so at least he would get something out of it, if Cygnus X-1 turned out not to be a black hole.
  25. ^ Cite error: The named reference su20040227 was invoked but never defined (see the help page).

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