Event Horizon Telescope Prepares To Take First Black Hole Picture

A simulation of what astronomer might see by looking at the event horizon by C-K Chan/D Psaltis/F Oze

Next year, astronomers will attempt something that has never been done before. They will try to photograph a black hole, but not just any black hole: Sagittarius A* – the supermassive black hole at the center of the Milky Way.

The project is called the Event Horizon Telescope (EHT), and links nine radio telescopes from across the world (including Chile, Spain, and the U.S.) that will act as a single telescope the size of Earth. The gigantic telescope will be able to look at the event horizon of a black hole. The team hopes to see gas swirling around the event horizon boundary.

Sagittarius A* has a mass equivalent to 4 million Suns, but it is not as big as you might think: Its diameter is 44 million kilometers (27 million miles), about 63 times the radius of the Sun. Its diminutive size is what makes the observations complex. It is 26,000 light-years away from us, so it has an apparent size in the sky of looking at a CD on the surface of the Moon from Earth.

"We're almost there. The phasing in of the instruments has been done, the receivers are in place and the theoretical work has been done,” said Professor Feryal Ozel, EHT team member, speaking to BBC News. "There are quite a few challenges that need to be overcome to take a picture of a black hole – it's something that's extremely small in the sky. But what we're hoping for is a full array observation in early 2017."

The event horizon is the boundary that separates the inside of the black hole from the rest of the universe. Anything that crosses the event horizon can’t escape the pull of the black hole. Around the event horizon, there’s a lot of gas being compressed by gravity and excited by the black hole's magnetic field, making observations complicated. The team decided to observe the event horizon using radio waves because they would be scattered less by the surrounding material.

"We've run upwards of a million simulations, for many different configurations of what that gas might look like. And in all cases, we think that the 1.3mm wavelength is the right choice to see down to the event horizon," added Ozel, who discussed the project at the 227th meeting of the American Astronomical Society.

The team is confident that the gas on the event horizon shines precisely at that wavelength, which is great news as our atmosphere is transparent at that wavelength.

The observation is going to be important for more than just a photograph. By studying how the supermassive black hole affects spacetime, the team will be able to test Einstein’s theory of relativity like never before.

[H/T: BBC News


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