A team of researchers used the balloon-borne XL-Calibur telescope to measure polarized X-rays from the black hole Cygnus X-1 in unprecedented detail, revealing new clues about how hot material twists, stretches, and glows as it is sucked into the black hole's center.
A team of physicists has collected new data that helps explain how matter falls into black holes and how these extreme environments release enormous amounts of light and energy.
They used a balloon telescope called XL-Calibur to observe Cygnus X-1, a famous black hole located about 7,000 light-years from Earth. “Scientists will use our observations to test new and increasingly realistic computer simulations of physical processes close to the black hole,” said physics professor Henryk Krawczynski.
how XL-Calibur tracks polarized X-rays
XL-Calibur is designed to measure the polarization of light, which refers to the direction in which electromagnetic vibrations occur. Tracking this direction helps scientists understand the structure and behavior of the extremely hot gas and debris that move rapidly around a black hole.
A recently published paper describes the results of observations of Cygnus X-1 and reports the most precise measurements yet of the polarization of the black hole's hard X-rays. "If we try to find Cygnus X-1 in the sky, we'll be looking for a really small point of X-ray radiation," said researcher Ephraim Gao. "Polarization is therefore useful for knowing everything that's happening around the black hole when it's impossible to take regular images from Earth."
These findings came from the XL-Calibur balloon flight in July 2024, which carried the telescope from Sweden to Canada.
Flight results in 2024 set records
In addition to the data from Cygnus X-1, the XL-Calibur team recently published new measurements of hard X-rays from the Crab Pulsar and its surrounding Wind Nebula, one of the brightest sources in the sky of continuous X-rays.
Kravchinsky noted that the 2024 mission had achieved several technical milestones, including high-quality measurements of Cygnus X-1 and the Crab pulsar. Professor Mark Pearce of the XL-Calibur team said: "Our observations of Cygnus X-1 and the Crab pulsar clearly show that the design of XL-Calibur is robust. I very much hope that we can now build on these successes with new Flower Ball flights."
The researchers plan to expand their research on the next XL-Calibur mission, scheduled to launch from Antarctica in 2027. They hope to collect data from more black holes and neutron stars, which will allow them to explore a wider range of high-energy cosmic environments.
"Together with data from NASA satellites like IXPE, we may soon have enough information to resolve long-standing questions about black hole physics in the coming years," added Kravchinsky, the project's principal investigator.
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