International cooperation of Japan and Sweden helped to clarify how gravity affects the shape of matter near a black hole in a binary system Cygnus X-1. Their findings, published in Nature Astronomy this month, will help scientists further understand the physics of strong gravity and evolution of black holes and galaxies.
Near the center of the constellation Cygnus is the star rotating around the first black hole discovered in the Universe. Together they form a binary system known as Cygnus X-1. This black hole is also one of the brightest x-ray sources in the sky. However, the geometry of matter, which generates the light was uncertain. The research team uncovered this information thanks to a new technique of x-ray polarimetry.
To make the black hole is not easy. First, a black hole cannot be seen because the light is to leave it can not. Instead of watching the black hole, scientists can observe the light emitted from the substance with her. In the case of Cygnus X-1 this light will emit a star near a black hole.
Most of the light that we see is vibrating in many directions. Polarization filters the light so that it will vibrate in the same direction. This is similar to how snow goggles with polarized lenses to help skiers to see where they come down from the mountain, because the filter disperses the snow, reflected from the snow.
“The same with the hard x-rays near a black hole,” says co-author Takahashi hiromitsu is the Executive. “But this filter penetrating hard x-rays and gamma-rays coming from black holes. From these rays no points will be saved, so we need another special device to measure this scattering of light”.
The team had to figure out where the light comes from and where it is dissipated. For both measurements we used the x-ray polarimeter for a balloon PoGO+. Two competing models describe how the substance along with the black hole in a binary system like Cygnus X-1: lamp pole and extended model. In the model lamp post crown is compact and is closely linked with the black hole. Photons are bent toward the accretion disk, which leads to more reflection of light. In rasshirennoi model crown more and is distributed around the black hole. The disk reflected light is weaker. The light is not strongly bent in the strong gravity of the black hole, a group of scientists has concluded that a black hole follows the model of the extended corona.