First-of-its-kind observation shows how jets from ravenous black holes can shape galaxy growth
By Lee Billings edited by Claire Cameron
Artist’s impression of the Cygnus X-1 system, which contains a supergiant star (LEFT) orbiting a black hole (RIGHT). The star’s strong stellar wind deflects the jets launched by the black hole, allowing astronomers to measure the power and speed of the jets.
International Center for Radio Astronomy Research
In a first for science, astronomers have observed the speed and power of matter flowing out of a black hole, shedding light on how this process shapes the structure of the universe.
Hungry black holes are the hidden architects of the cosmos. Nothing can escape from their depths, but as matter seeps in, a small fraction can rebel on the verge of oblivion and form two jets of terrifying power near the poles of the black hole which radiate into space. Bigger black holes produce bigger jets, and the biggest—supermassive black holes-can generate jets so huge that they influence entire groups of galaxies.
No direct hit is required; Shock waves from a jet can propagate hundreds of thousands of light years to turn galactic gas into stars or extinguish star formation altogether by expelling these reservoirs of gas into intergalactic space. Even a glance can tell the difference between a galaxy full of stars and no galaxy at all.
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Until now, no one had ever managed to directly measure the power of these planes. Using data from two international networks of radio telescopes, researchers were able to determine the energy of jets coming out of a black hole in a system called Swan X-1some 7,200 light years from Earth. Their results, published today in Natural astronomy, show that the black hole’s jets travel at about half the speed of light and carry about 10% of the total energy released by falling matter, equivalent to the power of 10,000 suns.
“Cygnus The system holds the first confirmed black holean object of about 20 solar masses that shoots out jets during its orbit and siphons gas from a supergiant star.
Combining observations collected over nearly two decades by the US Very Long Baseline Array (VLBA) and the European VLBI Network (EVN), Prabu and his colleagues were able to reconstruct high-resolution images of the jets over time, observing them buffeted back and forth by the intense stellar winds from the nearby star. “By combining all of these observations, we were able to reconstruct the ‘dancing’ motion of the jet and measure its properties in a way that had not been possible before,” says Prabu. The team’s discovery of the “curvature of black hole jets,” he says, “gave us a unique way to directly measure the power of the jets.”
James Miller-Jones, co-author of the study and an astrophysicist at the Curtin Institute for Radio Astronomy in Australia, notes that the result likely applies to black holes of all sizes. “Because our theories suggest that the physics around [all] “Black holes are very similar, we can now use this measurement to anchor our understanding of jets, whether they come from black holes 10 or 10 million times the mass of the sun,” he said. in a statement.
Previously, researchers inferred the strength of a black hole’s jets by observing how they affected their surroundings over thousands or even millions of years. These more fragmentary estimates informed large-scale cosmic simulations which model the growth and evolution of galaxies.
“It’s a really cool result,” says Rob Fender, an astrophysicist at the University of Oxford, who was not involved in the study. “Calibrating the power of black hole jets is really the key measurement for understanding how these objects have helped shape the cosmos, near and far. It’s notoriously difficult to do, and the results depend on assumptions about the matter content of the jets, the speed at which they move (harder to measure than one might think), and the density of the environment they enter.”
All of these hypotheses, Fender adds, are downplayed in the case of Cygnus X-1 because of everything we already know about the black hole’s companion star and its winds. In fact, the measurements the team made “are not really possible for any other system that we know of in the entire universe,” he says.
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