![]() ![]() ![]() "So, we're developing new algorithms that can specifically address that, to add a time variability to the modeling. "One of the challenges for Sagittarius A* is that it does evolve so quickly during the course of an evening," Doeleman said. Sgr A* is a relatively lightweight supermassive black hole, harboring the mass of "only" 4.3 million suns, and therefore operates on shorter timescales than the 6.5-billion-solar-mass M87 monster. And Sgr A* is a tougher target still, even though it's much closer to us (26,000 light-years versus 55 million light-years for M87). Such work is painstaking and time-consuming for example, the M87 data that enabled last year's image were gathered in 2017. (Photographing a black hole's interior is impossible, unless you're in there yourself, which is not advised.) The team devises algorithms to make sense of all this information, integrating it to generate an image depicting the black hole's event horizon - the "point of no return" beyond which nothing, not even light, can escape. The EHT combines data from eight radio telescopes around the world, which are linked to form a virtual megascope the size of Earth. Photographing a black hole is much more involved than just pointing and shooting. The EHT team has been observing Sgr A* but has not yet been able to generate an image from the data. "Even though I'm interested in what happens on the big scale, it all comes down to what's happening at the very small scale," Smethurst says.The next big moment could involve our own Milky Way galaxy's supermassive black hole, which is known as Sagittarius A*, or Sgr A* for short. That includes the types of atoms responsible for life as we know it on Earth, meaning black holes may even have a role in our own existence. In other words, what happens at the event horizon can influence what atoms get distributed throughout an entire galaxy. ![]() Sometimes the pressures get so great around the black hole that it can throw out material in a wind before it gets to the event horizon – and the energy that it expels affects the galaxy as a whole. "A black hole collects matter and grows by eating that matter up," says Becky Smethurst, an astronomer at Oxford University. ![]() The implications of this image go beyond testing general relativity, though. Today, he's one of the leaders of the theoretical side of the EHT - and says that the image is an amazing proof that Einstein was right. In 2000, astronomer Dimitrios Psaltis of the University of Arizona and his team calculated how to see the event horizon of a black hole. The theory of black holes, including the nature of real astronomical black holes, was developed by a large number of researchers over the past century. The M87 event horizon shape is precisely in agreement with the predictions of general relativity, including an estimate of how rapidly the black hole is rotating. The asymmetrical shape of the matter shows both the way plasma swirls around the event horizon, and also how the gravitational distortion of spacetime affects the path of the light emitted by the material. In a very real sense, the gravitational influence of a black hole is the way we can see it, and that's precisely what the EHT image reveals. ![]()
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