Cygnus X-1
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Cygnus |
| Right ascension | 19h 58m 21.67595s |
| Declination | +35° 12′ 05.7783″ |
| Apparent magnitude (V) | 8.95 |
| Characteristics | |
| Spectral type | O9.7Iab |
| U−B color index | −0.30 |
| B−V color index | +0.81 |
| Variable type | Ellipsoidal variable |
| Astrometry | |
| Radial velocity (Rv) | −13 km/s |
| Proper motion (μ) |
RA: −3.37 mas/yr Dec.: −7.15 mas/yr |
| Parallax (π) | 0.539 ± 0.033mas |
| Distance | 6,100 ± 400 ly (1,900 ± 100 pc) |
| Absolute magnitude (MV) | −6.5±0.2 |
| Details | |
| Mass | 14–16 M☉ |
| Radius | 20–22 R☉ |
| Luminosity | 3–4×105 L☉ |
| Surface gravity (log g) | 3.31±0.07 cgs |
| Temperature | 31000 K |
| Rotation | every 5.6 days |
| Age | 5 million years |
| Other designations | |
| Database references | |
| SIMBAD | data |
Cygnus X-1 (abbreviated Cyg X-1) is a galactic X-ray source in the constellation Cygnus, and the first such source widely accepted to be a black hole. It was discovered in 1964 during a rocket flight and is one of the strongest X-ray sources seen from Earth, producing a peak X-ray flux density of 2.3×10−23 Wm−2Hz−1 (2.3×103 Jansky). It remains among the most studied astronomical objects in its class. The compact object is now estimated to have a mass about 14.8 times the mass of the Sun and has been shown to be too small to be any known kind of normal star, or other likely object besides a black hole. If so, the radius of its event horizon is about 44 km.
Cygnus X-1 belongs to a high-mass X-ray binary system, located about 6070 light years from the Sun, that includes a blue supergiant variable star designated HDE 226868 which it orbits at about 0.2 AU, or 20% of the distance from the Earth to the Sun. A stellar wind from the star provides material for an accretion disk around the X-ray source. Matter in the inner disk is heated to millions of degrees, generating the observed X-rays. A pair of jets, arranged perpendicular to the disk, are carrying part of the energy of the infalling material away into interstellar space.
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