a black hole would be the only known example. While the combination of WR star and compact object would be unique, the WR component will itself almost certainly become a black hole very quickly by astronomical timescales. A supernova or possible direct collapse to a black hole is expected within a million years or so. However, modelling of the Cygnus X-3 system suggests it is most likely that the binary will be disrupted by any supernova event. The cosmic ray events from Cygnus X-3 had previously led to exotic proposals such as a star made of quarks, but are now explained as being produced in the relativistic jet. The explanation for the unusual relationship between the x-rays and the gamma-ray and radio flares is that the compact objects produces jets along its axis of rotation, within the dense wind from the WR star. These jets evacuate a cocoon within the wind when entering the hard state, and are then quenched by the wind when entering the soft state. Flares are produced during the transition to the hard state as the jets are interacting with the dense wind. Distance Cygnus X-3 lies in the direction of the Cygnus OB2 association in the Cygnus X complex, although it is much further away. Its distance can be estimated relative to Cygnus OB2 by studying the X-ray halo produced by dust between us and Cygnus X-3. The distance to Cygnus OB2 is not known precisely, but this method gives possible distances to Cygnus X-3 of or . There is a small X-ray source from Cygnus X-3 that varies with the same period by a phase lag of about . This is thought to be a Bok globule at approximately the same distance as Cygnus X-3. Using molecular line emission from this object, two possible distances are found to be and . A statistical mean is . See also List of nearest black holes References External links Cygnus X-3 and its Little Friend Chandra X-Ray Observatory A stellar circle of life near Cygnus X-3 Astronomy Now Waiting for Cygnus X-3 NASA Stellar black holes Cygnus (constellation) Microquasars X-ray astronomy Astronomical X-ray sources Cygni, V1521 Wolf–Rayet stars