Jump to content

Cygnus X-1

Coordinates:Sky map19h58m21.6756s,+35° 12′ 05.775″
From Wikipedia, the free encyclopedia
For other uses, seeCygnus X-1 (disambiguation).

Cygnus X-1
Location of Cygnus X-1 (circled)
Observation data
EpochJ2000EquinoxJ2000
Constellation Cygnus
Right ascension 19h58m21.67574s[1]
Declination +35° 12′ 05.7845″[1]
Apparent magnitude(V) 8.95[2]
Characteristics
Spectral type O9.7Iab[2]
U−Bcolor index −0.30[3]
B−Vcolor 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±0.015mas/yr[1]
Dec.:−6.310±0.017mas/yr[1]
Parallax(π)0.4439 ± 0.0149mas[1]
Distance7,300 ± 200ly
(2,250 ± 80pc)
Absolute magnitude(MV)−6.5±0.2[4]
Details
Cygnus X-1
Mass21.2[5][6]M☉
Details
HDE 226868
Mass20–40M☉
Radius20–22[7]R☉
Luminosity3–4×105[7]L☉
Surface gravity(logg)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,HIP98298,SAO69181, V1357 Cyg.[2]
Database references
SIMBADdata

Cygnus X-1(abbreviatedCyg X-1)[11]is a galacticX-ray sourcein theconstellationCygnusand was the first such source widely accepted to be ablack hole.[12][13]It was discovered in 1965 during arocket flightand is one of thestrongestX-ray sources detectable from Earth, producing a peak X-rayflux densityof2.3×10−23W/(m2⋅Hz)(2.3×103jansky).[14][15]It remains among the most studiedastronomical objectsin its class. The compact object is now estimated to have a mass about 21.2 times themass 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 itsevent horizonhas300km"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-massX-ray binarysystem, located about 2.22 kiloparsecsfrom theSun,[18]that includes a bluesupergiantvariable stardesignatedHDE 226868,[19]which it orbits at about 0.2 AU, or 20% of the distance from Earth to the Sun. Astellar windfrom the star provides material for anaccretion diskaround 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 ofrelativistic jets,arrangedperpendicularlyto the disk, are carrying part of the energy of the infalling material away into interstellar space.[23]

This system may belong to astellar associationcalled Cygnus OB3, which would mean that Cygnus X-1 is about 5 million years old and formed from aprogenitorstar that had more than40solar masses.The majority of the star's mass was shed, most likely as a stellar wind. If this star had then exploded as asupernova,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 physicistsStephen HawkingandKip Thornein 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 ablack holein the system. As of 2004,this hypothesis lacked direct empirical evidence but was generally accepted based on indirect evidence.[25]

Discovery and observation[edit]

Observation of X-ray emissions allowsastronomersto study celestial phenomena involving gas with temperatures in the millions of degrees. However, because X-ray emissions are blocked byEarth's atmosphere,observation ofcelestial X-ray sourcesis not possible without lifting instruments to altitudes where the X-rays can penetrate.[26][27]Cygnus X-1 was discovered usingX-ray instrumentsthat were carried aloft by asounding rocket launchedfromWhite Sands Missile RangeinNew Mexico.As part of an ongoing effort to map these sources, a survey was conducted in 1964 using twoAerobeesuborbital rockets. The rockets carriedGeiger countersto measure X-ray emission inwavelengthrange 1–15Åacross an 8.4° section of the sky. These instruments swept across the sky as the rockets rotated, producing a map of closely spaced scans.[11]

As a result of these surveys, eight new sources of cosmic X-rays were discovered, including Cyg XR-1 (later Cyg X-1) in the constellation Cygnus. Thecelestial coordinatesof this source were estimated asright ascension19h53manddeclination34.6°. It was not associated with any especially prominentradiooropticalsource at that position.[11]

Seeing a need for longer-duration studies, in 1963Riccardo GiacconiandHerb Gurskyproposed the first orbital satellite to study X-ray sources.NASAlaunched theirUhurusatellite in 1970,[28]which led to the discovery of 300 new X-ray sources.[29]Extended Uhuru observations of Cygnus X-1 showed fluctuations in the X-ray intensity that occurs several times a second.[30]This rapid variation meant that the X-ray generation must occur over a compact region no larger than ~105km(roughly the size ofJupiter),[31]as thespeed of lightrestricts communication between more distant regions.

In April–May 1971, Luc Braes and George K. Miley fromLeiden Observatory,and independently Robert M. Hjellming and Campbell Wade at theNational Radio Astronomy Observatory,[32]detected radio emission from Cygnus X-1, and their accurate radio position pinpointed the X-ray source to the star AGK2 +35 1910 = HDE 226868.[33][34]On thecelestial sphere,this star lies about half adegreefrom the4th-magnitudestarEta Cygni.[35]It is a supergiant star that is by itself incapable of emitting the observed quantities of X-rays. Hence, the star must have a companion that could heat gas to the millions of degrees needed to produce the radiation source for Cygnus X-1.

Louise WebsterandPaul Murdin,at theRoyal Greenwich Observatory,[36]andCharles Thomas Bolton,working independently at theUniversity of Toronto'sDavid Dunlap Observatory,[37]announced the discovery of a massive hidden companion to HDE 226868 in 1972. Measurements of theDoppler shiftof the star's spectrum demonstrated the companion's presence and allowed its mass to be estimated from the orbital parameters.[38]Based on the high predicted mass of the object, they surmised that it may be ablack hole,as the largest possibleneutron starcannot exceed three times themass of the Sun.[39]

With further observations strengthening the evidence, by the end of 1973 the astronomical community generally conceded that Cygnus X-1 was most likely a black hole.[40][41]More precise measurements of Cygnus X-1 demonstrated variability down to a singlemillisecond.This interval is consistent withturbulencein a disk of accreted matter surrounding a black hole—theaccretion disk.X-ray bursts that last for about a third of a second match the expected time frame of matter falling toward a black hole.[42]

X-ray image of Cygnus X-1 taken by a balloon-borne telescope, theHigh-Energy Replicated Optics(HERO) project

Cygnus X-1 has since been studied extensively using observations by orbiting and ground-based instruments.[2]The similarities between the emissions of X-ray binaries such as HDE 226868/Cygnus X-1 andactive galactic nucleisuggests a common mechanism of energy generation involving a black hole, an orbiting accretion disk and associatedjets.[43]For this reason, Cygnus X-1 is identified among a class of objects calledmicroquasars;an analog of thequasars,or quasi-stellar radio sources, now known to be distant active galactic nuclei. Scientific studies of binary systems such as HDE 226868/Cygnus X-1 may lead to further insights into the mechanics ofactive galaxies.[44]

Binary system[edit]

Thecompact objectandblue supergiantstar form abinary systemin which they orbit around theircenter of massevery 5.599829 days.[45]From the perspective of Earth, the compact object never goes behind the other star; in other words, the system does noteclipse.However, theinclination of the orbital planeto theline of sightfrom Earth remains uncertain, with predictions ranging from 27° to 65°. A 2007 study estimated the inclination as48.0±6.8°,which would mean that thesemi-major axisis about0.2AU,or 20% of the distance from Earth to the Sun. Theorbital eccentricityis thought to be only0.018±0.002,meaning a nearly circular orbit.[46][47]Earth's distance to this system is calculated by trigonometric parallax as 1,860 ± 120parsecs(6,070 ± 390light-years),[48]and by radio astrometry as 2,220 ± 170 parsecs (7,240 ± 550 ly).[5]

Ablue-bandlight curvefor Cygnus X-1, adapted from Kempet al.(1987)[49]

The HDE 226868/Cygnus X-1 system shares a common motion through space with an association of massive stars named Cygnus OB3, which is located at roughly 2000parsecsfrom the Sun. This implies that HDE 226868, Cygnus X-1 and thisOB associationmay have formed at the same time and location. If so, then the age of the system is about5±1.5 million years.The motion of HDE 226868 with respect to Cygnus OB3 is9±3km/s,a typical value for random motion within a stellar association. HDE 226868 is about60 parsecsfrom the center of the association and could have reached that separation in about7±2 million years—which roughly agrees with estimated age of the association.[10]

With agalactic latitudeof 4° andgalactic longitude71°,[2]this system lies inward along the sameOrion Spur,in which the Sun is located within theMilky Way,[50]near where the spur approaches theSagittarius Arm.Cygnus X-1 has been described as belonging to the Sagittarius Arm,[51]though the structure of the Milky Way is not well established.

Compact object[edit]

From various techniques, the mass of the compact object appears to be greater than the maximum mass for aneutron star.Stellar evolutionary models suggest a mass of20±5 solar masses,[7]while other techniques resulted in 10 solar masses. Measuring periodicities in the X-ray emission near the object yielded a more precise value of14.8±1 solar masses.In all cases, the object is most likely a black hole[46][52]—a region of space with agravitational fieldthat is strong enough to prevent the escape ofelectromagnetic radiationfrom the interior. The boundary of this region is called theevent horizonand has an effective radius called theSchwarzschild radius,which is about44 kmfor Cygnus X-1. Anything (includingmatterandphotons) that passes through this boundary is unable to escape.[53]New measurements published in 2021 yielded an estimated mass of21.2±2.2 solar masses.[5][6]

Evidence of just such an event horizon may have been detected in 1992 usingultraviolet(UV) observations with theHigh Speed Photometeron theHubble Space Telescope.As self-luminous clumps of matter spiral into a black hole, their radiation is emitted in a series of pulses that are subject togravitational redshiftas the material approaches the horizon. That is, thewavelengthsof the radiation steadily increase, as predicted bygeneral relativity.Matter hitting a solid, compact object would emit a final burst of energy, whereas material passing through an event horizon would not. Two such "dying pulse trains" were observed, which is consistent with the existence of a black hole.[54]

Chandra X-ray Observatoryimage of Cygnus X-1

The spin of the compact object is not yet well determined. Past analysis of data from the space-basedChandra X-ray Observatorysuggested that Cygnus X-1 was not rotating to any significant degree.[55][56]However, evidence announced in 2011 suggests that it is rotating extremely rapidly, approximately 790 times per second.[57]

Formation[edit]

The largest star in the Cygnus OB3 association has a mass 40 times that of the Sun. As more massive stars evolve more rapidly, this implies that the progenitor star for Cygnus X-1 had more than 40 solar masses. Given the current estimated mass of the black hole, the progenitor star must have lost over 30 solar masses of material. Part of this mass may have been lost to HDE 226868, while the remainder was most likely expelled by a strong stellar wind. Theheliumenrichment of HDE 226868's outer atmosphere may be evidence for this mass transfer.[58]Possibly the progenitor may have evolved into aWolf–Rayet star,which ejects a substantial proportion of its atmosphere using just such a powerful stellar wind.[10]

If the progenitor star had exploded as asupernova,then observations of similar objects show that the remnant would most likely have been ejected from the system at a relatively high velocity. As the object remained in orbit, this indicates that the progenitor may have collapsed directly into a black hole without exploding (or at most produced only a relatively modest explosion).[10]

Accretion disk[edit]

AChandraX-ray spectrum of Cygnus X-1 showing a characteristic peak near6.4keVdue toionizedironin the accretion disk, but the peak is gravitationally red-shifted, broadened by theDoppler effect,and skewed toward lower energies[59]

The compact object is thought to be orbited by a thin, flat disk of accreting matter known as anaccretion disk.This disk is intensely heated by friction between ionized gas in faster-moving inner orbits and that in slower outer ones. It is divided into a hot inner region with a relatively high level of ionization—forming aplasma—and a cooler, less ionized outer region that extends to an estimated 500 times the Schwarzschild radius,[22]or about 15,000 km.

Though highly and erratically variable, Cygnus X-1 is typically the brightest persistent source ofhard X-rays—those with energies from about 30 up to several hundred kiloelectronvolts—in the sky.[27]The X-rays are produced as lower-energy photons in the thin inner accretion disk, then given more energy throughCompton scatteringwith very high-temperatureelectronsin a geometrically thicker, but nearly transparentcoronaenveloping it, as well as by some further reflection from the surface of the thin disk.[60]An alternative possibility is that the X-rays may be Compton-scattered by the base of a jet instead of a disk corona.[61]

The X-ray emission from Cygnus X-1 can vary in a somewhat repetitive pattern calledquasi-periodic oscillations(QPO). The mass of the compact object appears to determine the distance at which the surrounding plasma begins to emit these QPOs, with the emission radius decreasing as the mass decreases. This technique has been used to estimate the mass of Cygnus X-1, providing a cross-check with other mass derivations.[62]

Pulsations with a stable period, similar to those resulting from the spin of a neutron star, have never been seen from Cygnus X-1.[63][64]Thepulsations from neutron starsare caused by the neutron star's rotating magnetic field, but theno-hair theoremguarantees that the magnetic field of a black hole is exactly aligned with its rotation axis and thus is static. For example, the X-ray binaryV 0332+53was thought to be a possible black hole until pulsations were found.[65]Cygnus X-1 has also never displayed X-ray bursts similar to those seen from neutron stars.[66]Cygnus X-1 unpredictably changes between two X-ray states, although the X-rays may vary continuously between those states as well. In the most common state, the X-rays are "hard", which means that more of the X-rays have high energy. In the less common state, the X-rays are "soft", with more of the X-rays having lower energy. The soft state also shows greater variability. The hard state is believed to originate in a corona surrounding the inner part of the more opaque accretion disk. The soft state occurs when the disk draws closer to the compact object (possibly as close as150 km), accompanied by cooling or ejection of the corona. When a new corona is generated, Cygnus X-1 transitions back to the hard state.[67]

The spectral transition of Cygnus X-1 can be explained using a two-componentadvectiveflow solution, as proposed by Chakrabarti and Titarchuk.[68]A hard state is generated by the inverse Comptonisation of seed photons from the Keplarian disk and likewise synchrotron photons produced by the hot electrons in the centrifugal-pressure–supported boundary layer (CENBOL).[69]

The X-ray flux from Cygnus X-1 varies periodically every 5.6 days, especially duringsuperior conjunctionwhen the orbiting objects are most closely aligned with Earth and the compact source is the more distant. This indicates that the emissions are being partially blocked by circumstellar matter, which may be the stellar wind from the star HDE 226868. There is a roughly 300-day periodicity in the emission, which could be caused by theprecessionof the accretion disk.[70]

Jets[edit]

As accreted matter falls toward the compact object, it losesgravitational potential energy.Part of this released energy is dissipated byjetsof particles, alignedperpendicularto the accretion disk, that flow outward withrelativisticvelocities (that is, the particles are moving at a significant fraction of thespeed of light). This pair of jets provide a means for an accretion disk to shed excess energy andangular momentum.They may be created bymagnetic fieldswithin the gas that surrounds the compact object.[71]

The Cygnus X-1 jets are inefficient radiators and so release only a small proportion of their energy in theelectromagnetic spectrum.That is, they appear "dark". The estimated angle of the jets to the line of sight is 30°, and they may beprecessing.[67]One of the jets is colliding with a relatively dense part of theinterstellar medium(ISM), forming an energized ring that can be detected by its radio emission. This collision appears to be forming anebulathat has been observed in theoptical wavelengths.To produce this nebula, the jet must have an estimated average power of 4–14×1036erg/s,or(9±5)×1029W.[72]This is more than 1,000 times the power emitted by the Sun.[73]There is no corresponding ring in the opposite direction because that jet is facing a lower-density region of theISM.[74]

In 2006, Cygnus X-1 became the first stellar-mass black hole found to display evidence ofgamma-rayemission in the very high-energy band, above100GeV.The signal was observed at the same time as a flare of hard X-rays, suggesting a link between the events. The X-ray flare may have been produced at the base of the jet, while the gamma rays could have been generated where the jet interacts with the stellar wind of HDE 226868.[75]

HDE 226868[edit]

An artist's impression of the HDE 226868–Cygnus X-1 binary system

HDE 226868 is a supergiant star with aspectral classof O9.7 Iab,[2]which is on the borderline between class-O and class-B stars. It has an estimated surface temperature of 31,000K[9]and mass approximately 20–40 times themass of the Sun.Based on a stellar evolutionary model, at the estimated distance of 2,000 parsecs, this star may have a radius equal to about 15–17[46]times thesolar radiusand has approximately 300,000–400,000 times theluminosity of the Sun.[7][76]For comparison, the compact object is estimated to be orbiting HDE 226868 at a distance of about 40 solar radii, or twice the radius of this star.[77]

The surface of HDE 226868 is beingtidallydistorted by thegravityof the massive companion, forming a tear-drop shape that is further distorted by rotation. This causes the optical brightness of the star to vary by 0.06 magnitudes during each 5.6-day binary orbit, with the minimum magnitude occurring when the system is aligned with the line of sight.[78]The "ellipsoidal" pattern of light variation results from thelimb darkeningandgravity darkeningof the star's surface.[79]

When the spectrum of HDE 226868 is compared to the similar starAlnilam,the former shows an overabundance ofheliumand an underabundance ofcarbonin its atmosphere.[80]Theultravioletandhydrogen- Alphaspectral lines of HDE 226868 show profiles similar to the starP Cygni,which indicates that the star is surrounded by a gaseous envelope that is being accelerated away from the star at speeds of about 1,500 km/s.[81][82]

Like other stars of its spectral type, HDE 226868 is thought to be shedding mass in astellar windat an estimated rate of2.5×10−6solar masses per year; or one solar mass every 400,000 years.[83]The gravitational influence of the compact object appears to be reshaping this stellar wind, producing a focused wind geometry rather than a spherically symmetrical wind.[77]X-rays from the region surrounding the compact object heat and ionize this stellar wind. As the object moves through different regions of the stellar wind during its 5.6-day orbit, the UV lines,[84]the radio emission,[85]and the X-rays themselves all vary.[86]

TheRoche lobeof HDE 226868 defines the region of space around the star where orbiting material remains gravitationally bound. Material that passes beyond this lobe may fall toward the orbiting companion. This Roche lobe is believed to be close to the surface of HDE 226868 but not overflowing, so the material at the stellar surface is not being stripped away by its companion. However, a significant proportion of the stellar wind emitted by the star is being drawn onto the compact object's accretion disk after passing beyond this lobe.[20]

The gas and dust between the Sun and HDE 226868 results in a reduction in the apparent magnitude of the star, as well as a reddening of the hue—red light can more effectively penetrate the dust in the interstellar medium. The estimated value of the interstellarextinction(AV) is 3.3magnitudes.[87]Without the intervening matter, HDE 226868 would be a fifth-magnitude star,[88]and thus visible to the unaided eye.[89]

Stephen Hawking and Kip Thorne[edit]

NASA's "Galaxy of Horrors" poster for Cygnus X-1[90]

Cygnus X-1 was the subject of a bet between physicistsStephen HawkingandKip Thorne,in which Hawking bet against the existence of black holes in the region. Hawking later described this as an "insurance policy" of sorts. In his bookA Brief History of Timehe wrote:[91]

This was a form of insurance policy for me. I have done a lot of work on black holes, and it would all be wasted if it turned out that black holes do not exist. But in that case, I would have the consolation of winning my bet, which would win me four years of the magazinePrivate Eye.If black holes do exist, Kip will get one year ofPenthouse.When we made the bet in 1975, we were 80% certain that Cygnus X-1 was a black hole. By now [1988], I would say that we are about 95% certain, but the bet has yet to be settled.

According to the updated tenth-anniversary edition ofA Brief History of Time,Hawking has conceded the bet[92]due to subsequent observational data in favor of black holes. In his own bookBlack Holes and Time Warps,Thorne reports that Hawking conceded the bet by breaking into Thorne's office while he was inRussia,finding the framed bet, and signing it.[93]While Hawking referred to the bet as taking place in 1975, the written bet itself (in Thorne's handwriting, with his and Hawking's signatures) bears additional witness signatures under a legend stating "Witnessed this tenth day of December 1974".[94]This date was confirmed by Kip Thorne on the January 10, 2018 episode ofNovaonPBS.[95]

In popular culture[edit]

Cygnus X-1 is the subject of atwo-part song seriesbyCanadianprogressive rockbandRush.The first part, "Book I: The Voyage", is the last song on the 1977 albumA Farewell to Kings.The second part, "Book II: Hemispheres", is the first song on the following 1978 album,Hemispheres.The lyrics describe an explorer aboard the spaceshipRocinante,who travels to the black hole, believing that there may be something beyond it. As he moves closer, it becomes increasingly difficult to control the ship, and he is eventually drawn in by the pull of gravity.[96]

In the 1979 Disney live-action science fiction filmThe Black Hole,the scientific survey ship captained by Dr. Hans Reinhardt to study the black hole of the film's title is theCygnus,presumably (although never stated as such) named for the first-identified black hole, Cygnus X-1.[97]

See also[edit]

References[edit]

  1. ^abcdVallenari, A.; et al. (Gaia collaboration) (2023)."GaiaData Release 3. Summary of the content and survey properties ".Astronomy and Astrophysics.674:A1.arXiv:2208.00211.Bibcode:2023A&A...674A...1G.doi:10.1051/0004-6361/202243940.S2CID244398875. Gaia DR3 record for this sourceatVizieR.
  2. ^abcdefgV* V1357 Cyg – High Mass X-ray Binary,Centre de Données astronomiques de Strasbourg, March 3, 2003,retrieved2008-03-03
  3. ^abBregman, J.; Butler, D.; Kemper, E.; Koski, A.; Kraft, R. P.; Stone, R. P. S. (1973), "Colors, magnitudes, spectral types and distances for stars in the field of the X-ray source Cyg X-1",Lick Observatory Bulletin,647:1,Bibcode:1973LicOB..24....1B
  4. ^Ninkov, Z.; Walker, G. A. H.; Yang, S. (1987),"The primary orbit and the absorption lines of HDE 226868 (Cygnus X-1)",Astrophysical Journal,321:425–437,Bibcode:1987ApJ...321..425N,doi:10.1086/165641,archived fromthe originalon 2017-09-22,retrieved2018-11-04
  5. ^abcdMiller-Jones, James C. A.; et al. (18 February 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.PMID33602863.S2CID231951746.Retrieved21 February2021.
  6. ^abcOverbye, Dennis(18 February 2021)."A Famous Black Hole Gets a Massive Update – Cygnus X-1, one of the first identified black holes, is much weightier than expected, raising new questions about how such objects form".The New York Times.Retrieved21 February2021.
  7. ^abcdZiółkowski, J. (2005), "Evolutionary constraints on the masses of the components of HDE 226868/Cyg X-1 binary system",Monthly Notices of the Royal Astronomical Society,358(3): 851–859,arXiv:astro-ph/0501102,Bibcode:2005MNRAS.358..851Z,doi:10.1111/j.1365-2966.2005.08796.x,S2CID119334761Note: for radius and luminosity, see Table 1 withd=2 kpc.
  8. ^Hadrava, Petr (September 15–21, 2007), "Optical spectroscopy of Cyg X-1",Proceedings of RAGtime 8/9: Workshops on Black Holes and Neutron Stars,Opava, Czech Republic: 71,arXiv:0710.0758,Bibcode:2007ragt.meet...71H
  9. ^abIntegral's view of Cygnus X-1,ESA, June 10, 2003,retrieved2008-03-20
  10. ^abcdeMirabel, I. Félix; Rodrigues, Irapuan (2003), "Formation of a Black Hole in the Dark",Science,300(5622): 1119–1120,arXiv:astro-ph/0305205,Bibcode:2003Sci...300.1119M,doi:10.1126/science.1083451,PMID12714674,S2CID45544180
  11. ^abcBowyer, S.; Byram, E. T.; Chubb, T. A.; Friedman, H. (1965), "Cosmic X-ray Sources",Science,147(3656): 394–398,Bibcode:1965Sci...147..394B,doi:10.1126/science.147.3656.394,PMID17832788,S2CID206565068
  12. ^Observations: Seeing in X-ray wavelengths,ESA, 2004-11-05,retrieved2008-08-12
  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. ^Lewin, Walter; Van Der Klis, Michiel (2006),Compact Stellar X-ray Sources,Cambridge University Press, p. 159,ISBN0-521-82659-4
  15. ^"2010 X-Ray Sources",The Astronomical Almanac,U.S. Naval Observatory, archived fromthe originalon 2010-03-28,retrieved2009-08-04gives a range of 235–1320 μJyat energies of 2–10 kEv,where aJansky(Jy) is10−26Wm−2Hz−1.
  16. ^The Illustrated Encyclopedia of the Universe.New York, NY: Watson-Guptill. 2001. p. 175.ISBN0-8230-2512-8.
  17. ^Harko, T. (June 28, 2006),Black Holes,University of Hong Kong, archived fromthe originalon February 10, 2009,retrieved2008-03-28
  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.PMID33602863.S2CID231951746.
  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.S2CID54841624.
  20. ^abGies, D. R.; Bolton, C. T. (1986), "The optical spectrum of HDE 226868 = Cygnus X-1. II — Spectrophotometry and mass estimates",The Astrophysical Journal,304:371–393,Bibcode:1986ApJ...304..371G,doi:10.1086/164171
  21. ^Nayakshin, Sergei; Dove, James B. (November 3, 1998), "X-rays From Magnetic Flares In Cygnus X-1: The Role Of A Transition Layer",arXiv:astro-ph/9811059
  22. ^abYoung, A. J.; Fabian, A. C.; Ross, R. R.; Tanaka, Y. (2001), "A Complete Relativistic Ionized Accretion Disc in Cygnus X-1",Monthly Notices of the Royal Astronomical Society,325(3): 1045–1052,arXiv:astro-ph/0103214,Bibcode:2001MNRAS.325.1045Y,doi:10.1046/j.1365-8711.2001.04498.x,S2CID14226526
  23. ^Gallo, Elena; Fender, Rob (2005), "Accretion modes and jet production in black hole X-ray binaries",Memorie della Società Astronomica Italiana,76:600–607,arXiv:astro-ph/0509172,Bibcode:2005MmSAI..76..600G
  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. ^Galaxy Entree or Main Course?,Swinburne University, February 27, 2004,retrieved2008-03-31
  26. ^Herbert, Friedman (2002), "From the ionosphere to high energy astronomy – a personal experience",The Century of Space Science,Springer,ISBN0-7923-7196-8
  27. ^abLiu, C. Z.; Li, T. P. (2004), "X-Ray Spectral Variability in Cygnus X-1",The Astrophysical Journal,611(2): 1084–1090,arXiv:astro-ph/0405246,Bibcode:2004ApJ...611.1084L,doi:10.1086/422209,S2CID208868049
  28. ^The Uhuru Satellite,NASA, June 26, 2003,retrieved2008-05-09
  29. ^Giacconi, Riccardo (December 8, 2002),The Dawn of X-Ray Astronomy,The Nobel Foundation,retrieved2008-03-24
  30. ^Oda, M.; Gorenstein, P.; Gursky, H.; Kellogg, E.; Schreier, E.; Tananbaum, H.; Giacconi, R. (1999), "X-Ray Pulsations from Cygnus X-1 Observed from UHURU",The Astrophysical Journal,166:L1–L7,Bibcode:1971ApJ...166L...1O,doi:10.1086/180726
  31. ^This is the distance light can travel in a third of a second.
  32. ^Kristian, J.; Brucato, R.; Visvanathan, N.; Lanning, H.; Sandage, A. (1971), "On the Optical Identification of Cygnus X-1",The Astrophysical Journal,168:L91–L93,Bibcode:1971ApJ...168L..91K,doi:10.1086/180790
  33. ^Braes, L. L. E.; Miley, G. K. (July 23, 1971), "Physical Sciences: Detection of Radio Emission from Cygnus X-1",Nature,232(5308): 246,Bibcode:1971Natur.232Q.246B,doi:10.1038/232246a0,PMID16062947,S2CID33340308
  34. ^Braes, L. L. E.; Miley, G. K. (1971), "Variable Radio Emission from X-Ray Sources",Veröffentlichungen Remeis-Sternwarte Bamberg,9(100): 173,Bibcode:1972VeBam.100......
  35. ^Abrams, Bernard; Stecker, Michael (1999),Structures in Space: Hidden Secrets of the Deep Sky,Springer, p. 91,ISBN1-85233-165-8,Eta Cygni is 25 arc minutes to the west-south-west of this star.
  36. ^Webster, B. Louise; Murdin, Paul (1972), "Cygnus X-1—a Spectroscopic Binary with a Heavy Companion?",Nature,235(5332): 37–38,Bibcode:1972Natur.235...37W,doi:10.1038/235037a0,S2CID4195462
  37. ^Bolton, C. T. (1972), "Identification of Cygnus X-1 with HDE 226868",Nature,235(5336): 271–273,Bibcode:1972Natur.235..271B,doi:10.1038/235271b0,S2CID4222070
  38. ^Luminet, Jean-Pierre (1992),Black Holes,Cambridge University Press,ISBN0-521-40906-3
  39. ^Bombaci, I. (1996), "The maximum mass of a neutron star",Astronomy and Astrophysics,305:871–877,arXiv:astro-ph/9608059,Bibcode:1996A&A...305..871B,doi:10.1086/310296,S2CID119085893
  40. ^Rolston, Bruce (November 10, 1997),The First Black Hole,University of Toronto, archived fromthe originalon March 7, 2008,retrieved2008-03-11
  41. ^Shipman, H. L.; Yu, Z.; Du, Y. W. (1975), "The implausible history of triple star models for Cygnus X-1 Evidence for a black hole",Astrophysical Letters,16(1): 9–12,Bibcode:1975ApL....16....9S,doi:10.1016/S0304-8853(99)00384-4
  42. ^Rothschild, R. E.; Boldt, E. A.; Holt, S. S.; Serlemitsos, P. J. (1974), "Millisecond Temporal Structure in Cygnus X-1",The Astrophysical Journal,189:77–115,Bibcode:1974ApJ...189L..13R,doi:10.1086/181452
  43. ^Koerding, Elmar; Jester, Sebastian; Fender, Rob (2006), "Accretion states and radio loudness in Active Galactic Nuclei: analogies with X-ray binaries",Monthly Notices of the Royal Astronomical Society,372(3): 1366–1378,arXiv:astro-ph/0608628,Bibcode:2006MNRAS.372.1366K,doi:10.1111/j.1365-2966.2006.10954.x,S2CID14833297
  44. ^Brainerd, Jim (July 20, 2005),X-rays from AGNs,The Astrophysics Spectator,retrieved2008-03-24
  45. ^Brocksopp, C.; Tarasov, A. E.; Lyuty, V. M.; Roche, P. (1999), "An Improved Orbital Ephemeris for Cygnus X-1",Astronomy & Astrophysics,343:861–864,arXiv:astro-ph/9812077,Bibcode:1999A&A...343..861B
  46. ^abcOrosz, Jerome (December 1, 2011), "The Mass of the Black Hole In Cygnus X-1",The Astrophysical Journal,742(2): 84,arXiv:1106.3689,Bibcode:2011ApJ...742...84O,doi:10.1088/0004-637X/742/2/84,S2CID18732012
  47. ^Bolton, C. T. (1975), "Optical observations and model for Cygnus X-1",The Astrophysical Journal,200:269–277,Bibcode:1975ApJ...200..269B,doi:10.1086/153785
  48. ^Reid, Mark J.; McClintock, Jeffrey E.; Narayan, Ramesh; Gou, Lijun; Remillard, Ronald A.; Orosz, Jerome A. (December 2011), "The Trigonometric Parallax of Cygnus X-1",The Astrophysical Journal,742(2): 83,arXiv:1106.3688,Bibcode:2011ApJ...742...83R,doi:10.1088/0004-637X/742/2/83,S2CID96429771
  49. ^Kemp, J. C.; Karitskaya, E. A.; Kumsiashvili, M. I.; Lyutyi, V. M.; Cherepashchuk, A. M. (April 1987)."Longperiod Optical Variability of the CYGNUS-X-1 System".Soviet Astronomy.31(2): 170.Bibcode:1987SvA....31..170K.Retrieved27 December2021.
  50. ^Gursky, H.; Gorenstein, P.; Kerr, F. J.; Grayzeck, E. J. (1971), "The Estimated Distance to Cygnus X-1 Based on its Low-Energy X-Ray Spectrum",Astrophysical Journal,167:L15,Bibcode:1971ApJ...167L..15G,doi:10.1086/180751
  51. ^Goebel, Greg,7.0 The Milky Way Galaxy,In The Public Domain, archived fromthe originalon 2008-06-12,retrieved2008-06-29
  52. ^Strohmayer, Tod; Shaposhnikov, Nikolai; Schartel, Norbert (May 16, 2007),New technique for 'weighing' black holes,ESA,retrieved2008-03-10
  53. ^Scientists find black hole's 'point of no return',Massachusetts Institute of Technology, January 9, 2006, archived fromthe originalon 13 January 2006,retrieved2008-03-28
  54. ^Dolan, Joseph F. (2001), "Dying Pulse Trains in Cygnus XR-1: Evidence for an Event Horizon?",The Publications of the Astronomical Society of the Pacific,113(786): 974–982,Bibcode:2001PASP..113..974D,doi:10.1086/322917
  55. ^Miller, J. M.; Fabian, A. C.; Nowak, M. A.; Lewin, W. H. G. (July 20–26, 2003), "Relativistic Iron Lines in Galactic Black Holes: Recent Results and Lines in the ASCA Archive",Proceedings of the 10th Annual Marcel Grossmann Meeting on General Relativity,Rio de Janeiro, Brazil, p. 1296,arXiv:astro-ph/0402101,Bibcode:2006tmgm.meet.1296M,doi:10.1142/9789812704030_0093,ISBN9789812566676,S2CID119336501{{citation}}:CS1 maint: location missing publisher (link)
  56. ^Roy, Steve; Watzke, Megan (September 17, 2003),""Iron-Clad" Evidence For Spinning Black Hole ",Chandra Press Release,Chandra press Room: 21,Bibcode:2003cxo..pres...21.,retrieved2008-03-11
  57. ^Gou, Lijun; McClintock, Jeffrey E.; Reid, Mark J.; Orosz, Jerome A.; Steiner, James F.; Narayan, Ramesh; Xiang, Jingen; Remillard, Ronald A.; Arnaud, Keith A.; Davis, Shane W. (November 9, 2011), "The Extreme Spin of the Black Hole in Cygnus X-1",The Astrophysical Journal,742(85),American Astronomical Society:85,arXiv:1106.3690,Bibcode:2011ApJ...742...85G,doi:10.1088/0004-637X/742/2/85,S2CID16525257
  58. ^Podsiadlowski, Philipp; Saul, Rappaport; Han, Zhanwen (2003), "On the formation and evolution of black-hole binaries",Monthly Notices of the Royal Astronomical Society,341(2): 385–404,arXiv:astro-ph/0207153,Bibcode:2003MNRAS.341..385P,doi:10.1046/j.1365-8711.2003.06464.x,S2CID119476943
  59. ^More Images of Cygnus X-1, XTE J1650-500 & GX 339-4,Harvard-Smithsonian Center for Astrophysics/Chandra X-ray Center, August 30, 2006,retrieved2008-03-30
  60. ^Ling, J. C.; Wheaton, Wm. A.; Wallyn, P.; Mahoney, W. A.; Paciesas, W. S.; Harmon, B. A.; Fishman, G. J.; Zhang, S. N.; Hua, X. M. (1997), "Gamma-Ray Spectra and Variability of Cygnus X-1 Observed by BATSE",The Astrophysical Journal,484(1): 375–382,Bibcode:1997ApJ...484..375L,doi:10.1086/304323
  61. ^Kylafis, N.; Giannios, D.; Psaltis, D. (2006), "Spectra and time variability of black-hole binaries in the low/hard state",Advances in Space Research,38(12): 2810–2812,Bibcode:2006AdSpR..38.2810K,doi:10.1016/j.asr.2005.09.045
  62. ^Titarchuk, Lev; Shaposhnikov, Nikolai (February 9, 2008), "On the nature of the variability power decay towards soft spectral states in X-ray binaries. Case study in Cyg X-1",The Astrophysical Journal,678(2): 1230–1236,arXiv:0802.1278,Bibcode:2008ApJ...678.1230T,doi:10.1086/587124,S2CID5195999
  63. ^Fabian, A. C.; Miller, J. M. (August 9, 2002), "Black Holes Reveal Their Innermost Secrets",Science,297(5583): 947–948,doi:10.1126/science.1074957,PMID12169716,S2CID118027201
  64. ^Wen, Han Chin (March 1998),Ten Microsecond Time Resolution Studies of Cygnus X-1,Stanford University, p. 6,Bibcode:1997PhDT.........6W
  65. ^Stella, L.; White, N. E.; Davelaar, J.; Parmar, A. N.; Blissett, R. J.; van der Klis, M. (1985),"The discovery of 4.4 second X-ray pulsations from the rapidly variable X-ray transient V0332 + 53"(PDF),Astrophysical Journal Letters,288:L45–L49,Bibcode:1985ApJ...288L..45S,doi:10.1086/184419
  66. ^Narayan, Ramesh (2003), "Evidence for the black hole event horizon",Astronomy & Geophysics,44(6): 77–115,arXiv:gr-qc/0204080,Bibcode:2003A&G....44f..22N,doi:10.1046/j.1468-4004.2003.44622.x
  67. ^abTorres, Diego F.; Romero, Gustavo E.; Barcons, Xavier; Lu, Youjun (2005), "Probing the Precession of the Inner Accretion Disk in Cygnus X-1",The Astrophysical Journal,626(2): 1015–1019,arXiv:astro-ph/0503186,Bibcode:2005ApJ...626.1015T,doi:10.1086/430125,S2CID16569507
  68. ^S. K. Chakrabarti; L. G. Titarchuk (1995). "Spectral Properties of Accretion Disks around Galactic and Extragalactic Black Holes".Astrophysical Journal.455:623–668.arXiv:astro-ph/9510005v2.Bibcode:1995ApJ...455..623C.doi:10.1086/176610.S2CID18151304.
  69. ^S. K. Chakrabarti; S. Mandal (2006)."The Spectral Properties of Shocked Two-Component Accretion Flows in the Presence of Synchrotron Emission".The Astrophysical Journal.642(1): L49–L52.Bibcode:2006ApJ...642L..49C.doi:10.1086/504319.S2CID122610073.
  70. ^Kitamoto, S.; E. Wataru, E.; Miyamoto, S.; Tsunemi, H.; Ling, J. C.; Wheaton, W. A.; Paul, B. (2000), "GINGAAll-Sky Monitor Observations of Cygnus X-1 ",The Astrophysical Journal,531(1): 546–552,Bibcode:2000ApJ...531..546K,doi:10.1086/308423
  71. ^Begelman, Mitchell C. (2003), "Evidence for Black Holes",Science,300(5627): 1898–1903,Bibcode:2003Sci...300.1898B,doi:10.1126/science.1085334,PMID12817138,S2CID46107747
  72. ^Russell, D. M.; Fender, R. P.; Gallo, E.; Kaiser, C. R. (2007), "The jet-powered optical nebula of Cygnus X-1",Monthly Notices of the Royal Astronomical Society,376(3): 1341–1349,arXiv:astro-ph/0701645,Bibcode:2007MNRAS.376.1341R,doi:10.1111/j.1365-2966.2007.11539.x,S2CID18689655
  73. ^Sackmann, I.-Juliana; Boothroyd, Arnold I.; Kraemer, Kathleen E. (1993), "Our Sun. III. Present and Future",The Astrophysical Journal,418:457–468,Bibcode:1993ApJ...418..457S,doi:10.1086/173407
  74. ^Gallo, E.; Fender, Rob; Kaiser, Christian; Russell, David;Morganti, Raffaella;Oosterloo, Tom; Heinz, Sebastian (2005), "A dark jet dominates the power output of the stellar black hole Cygnus X-1",Nature,436(7052): 819–821,arXiv:astro-ph/0508228,Bibcode:2005Natur.436..819G,doi:10.1038/nature03879,PMID16094361,S2CID4404783
  75. ^Albert, J.; et al. (2007), "Very High Energy Gamma-ray Radiation from the Stellar-mass Black Hole Cygnus X-1",Astrophysical Journal Letters,665(1): L51–L54,arXiv:0706.1505,Bibcode:2007ApJ...665L..51A,doi:10.1086/521145,S2CID15302221
  76. ^Iorio, Lorenzo (2008), "On the orbital and physical parameters of the HDE 226868/Cygnus X-1 binary system",Astrophysics and Space Science,315(1–4): 335–340,arXiv:0707.3525,Bibcode:2008Ap&SS.315..335I,doi:10.1007/s10509-008-9839-y,S2CID7759638
  77. ^abMiller, J. M.; Wojdowski, P.; Schulz, N. S.; Marshall, H. L.; Fabian, A. C.; Remillard, R. A.; Wijnands, R.; Lewin, W. H. G. (2005), "Revealing the Focused Companion Wind in Cygnus X-1 withChandra",The Astrophysical Journal,620(1): 398–404,arXiv:astro-ph/0208463,Bibcode:2005ApJ...620..398M,doi:10.1086/426701,S2CID51806148
  78. ^Caballero, M. D. (16–20 February 2004), "OMC-INTEGRAL: Optical Observations of X-Ray Sources",Proceedings of the 5th INTEGRAL Workshop on the INTEGRAL Universe (ESA SP-552). 16–20 February 2004,552,Munich, Germany: ESA: 875–878,Bibcode:2004ESASP.552..875C
  79. ^Cox, Arthur C. (2001),Allen's Astrophysical Quantities,Springer, p. 407,ISBN0-387-95189-X
  80. ^Canalizo, G.; Koenigsberger, G.; Peña, D.; Ruiz, E. (1995), "Spectral variations and a classical curve-of-growth analysis of HDE 226868 (Cyg X-1)",Revista Mexicana de Astronomía y Astrofísica,31(1): 63–86,Bibcode:1995RMxAA..31...63C
  81. ^Conti, P. S. (1978), "Stellar parameters of five early type companions of X-ray sources",Astronomy and Astrophysics,63:225,Bibcode:1978A&A....63..225C
  82. ^Sowers, J. W.; Gies, D. R.; Bagnuolo, W. G.; Shafter, A. W.; Wiemker, R.; Wiggs, M. S. (1998), "Tomographic Analysis of Hα Profiles in HDE 226868/Cygnus X-1",The Astrophysical Journal,506(1): 424–430,Bibcode:1998ApJ...506..424S,doi:10.1086/306246
  83. ^Hutchings, J. B. (1976), "Stellar winds from hot supergiants",The Astrophysical Journal,203:438–447,Bibcode:1976ApJ...203..438H,doi:10.1086/154095
  84. ^Vrtilek, Saeqa D.; Hunacek, A.; Boroson, B. S. (2006), "X-Ray Ionization Effects on the Stellar Wind of Cygnus X-1",Bulletin of the American Astronomical Society,38:334,Bibcode:2006HEAD....9.0131V
  85. ^Pooley, G. G.; Fender, R. P.; Brocksopp, C. (1999), "Orbital modulation and longer-term variability in the radio emission from Cygnus X-1",Monthly Notices of the Royal Astronomical Society,302(1): L1–L5,arXiv:astro-ph/9809305,Bibcode:1999MNRAS.302L...1P,doi:10.1046/j.1365-8711.1999.02225.x,S2CID2123824
  86. ^Gies, D. R.; Bolton, C. T.; Thomson, J. R.; Huang, W.; McSwain, M. V.; Riddle, R. L.; Wang, Z.; Wiita, P. J.; Wingert, D. W.; Csák, B.; Kiss, L. L. (2003), "Wind Accretion and State Transitions in Cygnus X-1",The Astrophysical Journal,583(1): 424–436,arXiv:astro-ph/0206253,Bibcode:2003ApJ...583..424G,doi:10.1086/345345,S2CID6241544
  87. ^Margon, Bruce; Bowyer, Stuart; Stone, Remington P. S. (1973), "On the Distance to Cygnus X-1",The Astrophysical Journal,185(2): L113–L116,Bibcode:1973ApJ...185L.113M,doi:10.1086/181333
  88. ^Interstellar Reddening,Swinburne University of Technology,retrieved2006-08-10
  89. ^Kaler, Jim,Cygnus X-1,University of Illinois,retrieved2008-03-19
  90. ^"Devoured by Gravity".NASA.Retrieved15 April2021.
  91. ^Hawking, Stephen (1988),A Brief History of Time,Bantam Books,ISBN0-553-05340-X
  92. ^Hawking, Stephen (1998),A Brief History of Time(Updated and Expanded Tenth Anniversary ed.), Bantam Doubleday Dell Publishing Group,ISBN0-553-38016-8
  93. ^Thorne, Kip (1994),Black Holes and Time Warps: Einstein's Outrageous Legacy,W. W. Norton & Company,ISBN0-393-31276-3
  94. ^Vaughan, Simon."Hawking Thorne wager".University of Leicester.Archived fromthe originalon 13 May 2020.Retrieved4 February2018.
  95. ^"Black Hole Apocalypse".PBS.org.10 January 2018.Retrieved4 February2018.
  96. ^Rush and Philosophy: Heart and Mind United.Open Court. 2011. p. 196.
  97. ^Hogan, David J.Science Fiction America: Essays on SF Cinema.McFarland. p. 231.

External links[edit]

Wikimedia Commons has media related toCygnus X-1.
Records
Preceded by
None
Cyg X-1 is the first black hole discovered
 Least distant black hole
1972—1986 		Succeeded by
Retrieved from "https://en.wikipedia.org/w/index.php?title=Cygnus_X-1&oldid=1234906469"