In this simulation of a supermassive black hole fusion, the closest black hole to the viewer, shifted to blue, amplifies the red hole shifted to red at the rear by gravity lenses. The researchers found a clear decrease in brightness as the nearest black hole passed in the shadow of its counterpart, an observation that can be used to measure the size of both black holes and to test alternative theories of gravity. Credit: Jordi Davelaar
In a pair of merging supermassive black holes, a new method of measuring emptiness
Scientists have found a way to scale the “shadows” of two supermassive black holes in a collision process, giving astronomers a potentially new tool for measuring black holes in distant galaxies and testing alternative theories of gravity.
Three years ago, the world was stunned by the first image of a black hole. A black pit of nothingness, surrounded by a ring of fire of light. This iconic image of the black hole in the center of the Messier 87 galaxy came into focus thanks to the Event Horizon Telescope (EHT), a global network of synchronized radios acting as one giant telescope.
Now a couple of researchers from Colombia have come up with a potentially easier way to look into the abyss. Outlined in additional research in Physical Review Letters and Physical Review D, their imaging technique could allow astronomers to study black holes smaller than M87, a monster with a mass of 6.5 billion suns, housed in galaxies farther away. of the M87, which is 55 million light-years away, is still relatively close to our Milky Way.
Simulation of gravitational lenses in a pair of merging supermassive black holes. Credit: Jordi Devalair
The technique has only two requirements. First, you need a pair of supermassive black holes in the pain of merging. Second, you need to look at the couple from almost a side angle. From this lateral point of view, when one black hole passes in front of another, you should be able to see a bright flash as the glowing ring of the black hole magnifies farther from the nearest black hole, a phenomenon known as gravitational lenses.
The effect of lenses is well known, but what the researchers found here was a hidden signal: a distinctive drop in brightness corresponding to the “shadow” of the black hole at the back. This subtle eclipse can last from several hours to several days, depending on how massive the black holes are and how closely their orbits are intertwined. If you measure how long the decline lasts, researchers say, you can estimate the size and shape of the shadow cast from the event horizon of the black hole, the dead end point where nothing comes out, not even light.
In this simulation of a pair of merging supermassive black holes, the black hole closest to the viewer approaches and thus appears blue (frame 1), amplifying the reddish black hole at the rear by gravity lenses. As the nearest black hole amplifies the light of the black hole farther (frame 2), the viewer sees a bright flash. But when the nearest black hole passes in front of the abyss or shadow of the farthest black hole, the viewer sees a slight decrease in brightness (frame 3). This decrease in brightness (3) is clearly seen in the light curve data below the images. Credit: Jordi Devalair
“It took years and a lot of effort by dozens of scientists to make this high-resolution image of M87 black holes,” said the study’s first author, Jordi Davelaar, a postdoc at Colombia and the Flatiron Institute’s Center for Computational Astrophysics. “This approach only works for the biggest and closest black holes – the pair at the heart of the M87 and potentially our own Milky Way.”
He added: “With our technique you measure the brightness of black holes over time, you do not need to resolve each object spatially. It should be possible to find this signal in many galaxies. “
The shadow of a black hole is both its most mysterious and informative feature. “This dark spot tells us about the size of the black hole, the shape of space-time around it, and how matter falls into the black hole near its horizon,” said co-author Zoltan Hyman, a professor of physics in Colombia.
Observing a supermassive fusion of a black hole from the side, the black hole closest to the viewer magnifies the black hole farther through the gravitational lens effect. Researchers have found a brief drop in brightness, corresponding to the “shadow” of the black hole farther away, allowing the viewer to measure its size. Credit: Nicoletta Baroloini
The shadows of black holes can also hide the secret of the true nature of gravity, one of the main forces of our universe. Einstein’s theory of gravity, known as the general theory of relativity, predicts the size of black holes. Therefore, physicists have sought them out to test alternative theories of gravity in an attempt to reconcile two competing ideas about how nature works: Einstein’s general theory of relativity, which explains large-scale phenomena such as orbital planets and the expanding universe, and quantum physics. which explains how small particles such as electrons and photons can occupy multiple states at once.
Researchers are interested in the eruption of supermassive black holes after spotting a putative pair of supermassive black holes at the center of a distant galaxy in the early universe. NASA’s Kepler Space Telescope scanned for small drops in brightness corresponding to a planet passing in front of a host star. Instead, Kepler eventually discovers the eruptions of what Hyman and his colleagues claim are a pair of merging black holes.
They named the distant galaxy “Spikey” for the peaks in brightness caused by its supposed black holes, which magnify each other with each full rotation through the lens effect. To learn more about lightning, Hyman built a model with his postdock Davelaar.
However, they were confused when their simulated pair of black holes caused an unexpected but periodic drop in brightness each time one orbited in front of another. At first they thought it was a coding error. But further checks made them trust the signal.
As they searched for a physical mechanism to explain it, they realized that any drop in brightness coincided with the time it took for the black hole closest to the viewer to pass in front of the shadow of the black hole behind.
Researchers are currently looking at other telescopic data to try to confirm the drop they saw in Kepler’s data to confirm that Spike is actually hiding a pair of merging black holes. If all goes well, the technique could be applied to a handful of other alleged pairs of merging supermassive black holes among the 150 or so that have been spotted so far awaiting confirmation.
As more powerful telescopes appear online in the coming years, other possibilities may arise. The Vera Rubin Observatory, due to open this year, has views of more than 100 million supermassive black holes. Further exploration of black holes will be possible when NASA’s gravitational wave detector, LISA, is launched into space in 2030.
“Even if only a small fraction of these binary black holes have the right conditions to measure our proposed effect, we could find many of these black hole declines,” Davelaar said.
References:
Self-Reflecting Reflections of Black Hole Binary Elements: Observing Black Hole Shadows by Light Curve Tomography by Jordi Davelaar and Zoltan Hyman, May 9, 2022, Physical Review Letters.DOI: 10.1103 / PhysRevLett.128.191101
“Self-objective reflections of binary black hole systems: General relativistic tracking of binary binary black hole rays” by Jordi Davelaar and Zoltan Hyman, May 9, 2022, Physical Review D.DOI: 10.1103 / PhysRevD.105.103010
Add Comment