What is Cygnus X-1?

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About Cygnus X-1:

It was discovered over four decades ago.
It is one of the first confirmed black hole systems in our galaxy.
The black hole in Cygnus X-1 is 20 times heavier than the Sun, and has a companion – a heavy supergiant star (40 times more massive than the Sun) in a binary system.
It is located at a distance that is about 400 times more than the distance between Earth and Sun.
Due to the gravitational pull of the black hole, material from the supergiant falls and spirals in towards the black hole.
This process leads to the formation of a thin accretion disk which is responsible for soft X-rays.

Significance of X-ray Polarisation

Normal X-ray measurements only reveal the energy or intensity of the radiations.
Polarisation characteristics of X-rays, which tells about the orientation of the oscillating electric field, holds clues on the geometry and other properties of the black hole.
This measurement of high polarization in this source in the 100-380 keV implies that radiation emitted from the source at energies above 100 keV, is likely to have originated at the black hole jet
Polarization is one of the properties that a photon carries from the celestial objects in the sky.

Q1: What are X-rays?

X-rays are a form of electromagnetic radiation, similar to visible light. Unlike light, however, x-rays have higher energy and can pass through most objects, including the body. Medical x-rays are used to generate images of tissues and structures inside the body.