The black hole in Cygnus X-1 is one of the brightest sources of x-rays in the sky. Light near the black hole comes from matter being pumped from the satellite
Collaboration between Japanese and Swedish scientists revealed how gravity affects the form of matter near a black hole in the Cygnus X-1 binary system. These results will help to understand the physics of powerful gravity and the evolution of black holes and galaxies.
Near the center of the constellation Cygnus is a star rotating around the first black hole found in the universe. Together they form a double system Cygnus X-1. This black hole also plays the role of the brightest X-ray source in the sky. But the geometry of matter generating light remained uncertain. Researchers used X-ray polarimetry to sort out this issue.
Take a picture of a black hole is not easy. First of all, it is impossible to observe the object, because black light cannot escape. Therefore, it is necessary to tune in to the light emanating from matter close to a black hole. The situation with Cygnus X-1 is about a black hole spinning around. Light vibrates in many directions.
Polarization filters light so that it vibrates in one direction. The filter transmits x-rays and gamma rays coming from a black hole. The team had to figure out where the light comes from and where it scatters. To perform both measurements, they launched an X-ray polarimeter in a PoGO + balloon. From there, scientists could determine how much of the X-rays were reflected from the accretion disk.
Two competing models describe how matter near a black hole can look like in a binary system: a lamp pole and an extended model. The first is that the crown is compact and the dough is connected to a black hole. The photons bend to the accretion disk, which leads to more reflected light. In the expanded model, the corona is larger and spreads around the black hole. Then the reflected light on the disc is weaker.
The artistic vision of two competing models: the lamp pole and the extended one. The black dot is a black hole, blue is its accretion disk, and the red is the crown
Since the light did not bend so strongly under the powerful gravity of the black hole, the researchers concluded that the expanded model worked. This information will help to get more characteristics of black holes. For example, their rotation. The rotation effect can change the space-time around the black hole and give a hint to the evolution process.