An international team of astronomers has unveiled new insights into the enigmatic Cygnus X-3 binary system, located approximately 24,000 light-years away in the Milky Way galaxy. Utilizing NASA’s Imaging X-ray Polarimetry Explorer (IXPE), researchers have made a remarkable discovery: this system, believed to harbor a black hole and a massive Wolf-Rayet star, exhibits an X-ray emission pattern strikingly similar to some of the universe’s most luminous quasars.
First detected in the early 1970s through powerful radio jets that periodically switch on and off, Cygnus X-3 has remained a captivating celestial object. Despite being shrouded in thick dust obscuring its visible light, further observations in radio, infrared, and X-ray wavelengths revealed it to be an X-ray binary system. This intriguing system involves the transfer of matter between a massive star and a compact object, either a neutron star or a black hole, orbiting a common center of gravity.
One of the study’s key findings, led by Alexandra Veledina of the University of Turku in Finland, is the amplification of X-ray emission by a funnel-shaped cavity surrounding the probable black hole. Veledina explained, “We have discovered that the compact object is surrounded by an envelope of dense, opaque matter. The light that we observe is a reflection off the inner funnel walls formed by the surrounding gas, resembling a cup with a mirror interior.”
The system’s luminosity is particularly intriguing as it appears to defy the Eddington Limit, a theoretical threshold defining the maximum matter accretion rate by a black hole before radiation pressure halts further infall. Cygnus X-3’s behavior mirrors that of ultra-luminous X-ray sources (ULXs) found in distant galaxies, whose emissions are similarly amplified by a surrounding funnel.
The study discovered that the X-ray light’s polarization degree varies with the system’s activity, reaching 24.9 percent during its ULX phase and decreasing to 10.4 percent when less active. This fluctuation suggests the funnel structure is influenced by the amount of accretion. A significant decrease in infalling material could lead to the funnel’s collapse, only to reform when accretion resumes.
The team’s findings, published in the journal Nature Astronomy, offer a more refined model for comprehending distant ULXs and provide a framework for future observations aiming to capture the predicted funnel collapse in real-time. This research underscores the importance of studying celestial objects like Cygnus X-3 to unravel the complex interplay between black holes, stellar environments, and the emission of high-energy radiation.
