In 1961 astronomers found a strong x-ray supply coming from the constellation Cygnus. Not figuring out what it was, they named the supply Cygnus X-1. It’s one of many strongest x-ray sources within the sky, and we now know it’s powered by a stellar-mass black gap. Since it’s only about 7,000 light-years away, it additionally provides astronomers a wonderful view of how stellar-mass black holes behave. Even after six many years of examine, it continues to show us a couple of issues, as a current examine in Science exhibits.
Cygnus X-1 is definitely a binary system. The black gap itself is a 21 solar-mass stellar remnant, and it orbits a 41 solar-mass companion star. It’s a strong x-ray supply as a result of materials from the star is captured into an accretion disk of the black gap, which superheats the fabric and generates jets of plasma that move away from the black gap. This can be a frequent scenario for black holes, however astronomers nonetheless don’t perceive all the small print of how the sort of construction evolves.
For this examine, the workforce used knowledge from the Imaging X-Ray Polarimetry Explorer (IXPE), which may seize not simply x-rays but in addition their polarization. Once they mixed this knowledge with different observations of Cygnus X-1, they discovered the x-rays are emitted not from the areas alongside the jets, however from a 2,000 km area perpendicular to the jets. In different phrases, the accretion disk itself is the first x-ray supply. This helps the mannequin the place the innermost area of the accretion disk is what powers a black gap’s jets.
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This X-ray picture of Cygnus X-1 was taken by a balloon-borne telescope, the Excessive Vitality Replicated Optics (HERO) undertaking. NASA picture.
The workforce additionally discovered that the orientation of the accretion disk is tilted considerably relative to the orbital airplane of the binary system. It will be uncommon for members of a stellar binary system to have such differing rotational axes, so it’s doubtless that the shift occurred in the course of the cataclysmic explosion that fashioned the black gap.
Understanding that the x-ray supply is comparatively near the black gap, astronomers can additional examine their dynamics to higher perceive how black holes have an effect on the warping of area and time, which may result in extra stringent assessments of common relativity.
Reference: Krawczynski, Henric, et al. “Polarized x-rays constrain the disk-jet geometry within the black gap x-ray binary Cygnus X-1” Science (2022): 5399.
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