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How do you take a picture of a black hole? A UMass astronomer explains.





Researchers from across the globe have officially begun the process of imaging one of the most camera shy subjects in the galaxy: a black hole.

Or, to be more specific, the edge of a black hole. The project, known as Event Horizons Telescope, started April 5 and will continue until Friday, April 14, with a team of scientists stationed in six observatories across the planet all training their telescopes on Sagittarius A*, our Milky Way’s own local (and massive) black hole.

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Gopal Narayanan, an astronomy research professor at the University of Massachusetts Amherst and a member of the Event Horizons team, is carrying out his portion of the project from Mexico. “It’s totally unprecedented,” he said. “A project of this scale has not been done before.”

The black hole being studied has a mass that’s more than 4 million times that of the sun, but given its distance from Earth — roughly 26,000 light years — and the fact that it absorbs all light, no one has ever managed to capture an image of it. The Event Horizons Telescope team hopes to change that by focusing on the event horizon, that is, the point on a black hole beyond which no light can escape.

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Black holes are surrounded by incredibly hot and bright plasma, which can create a shadow of sorts behind the black hole that scientists can observe at specific wavelengths. If the team can capture that silhouette along the edge, it will serve as definitive evidence that black holes exist and could pave the way for a wave of other discoveries.

To do so, however, the scientists need an enormously powerful telescope. Like, a planet-sized one. Or at least something close. “Of course, we can’t actually build a telescope as big as Earth,” said Narayanan. “So, we do the next best thing. We put telescopes around the world and sample from each.”

Each observatory will then send their observations to command central in Cambridge, located at the Harvard Smithsonian Center for Astrophysics, according to Narayanan. From there, a fleet of supercomputers will be in charge of compiling everything into the final image.

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Don’t expect it overnight. It could take six months or longer for the image to be processed. This is one of the largest collections of data in physics history, meaning the observatories can’t just send their information over email. They’ll have to physically ship each of their drives to Cambridge.

This won’t be a problem for most of the Event Horizons Telescope team, but one of the observatories is located in the South Pole, which is in the midst of its winter. “[The obsevatory] is inaccesible. You can’t fly in or out until August or September, when winter ends. We can continue with the analysis of the rest of the data, but the South Pole contributes an important baseline,” said Narayanan.

But that’s a problem for the future. Right now, the scientists are working long hours to make sure they take care of their part. In the first couple days, Narayanan and the rest of the team in Mexico were starting their observations at roughly 4:30 p.m. and ending at 10:30 the next morning, splitting into two shifts. Sleep is not plentiful, in other words. But Naryanan isn’t complaning.

“It’s very exciting,” the UMass astronomer said. “We’ll be opening up new vantage points into our universe.”

Alex Frandsen can be reached at alexander.frandsen@globe.com.


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