Next week, the European Southern Observatory is going to make a big announcement, and no one is sure exactly what it’s going to be. However, there are some possibilities, and the most exciting one is that the ESO is about to reveal the first-ever photograph of the event horizon of a black hole.
Taking a photo of a black hole is not an easy task. Not only are black holes famous for not letting any light escape, even the nearest known black holes are very far away. The specific black hole astronomers wanted to photograph, Sagittarius A*, lies at the center of our galaxy 25,000 light-years away.
The ESO announced their plan to photograph Sagittarius A* back in 2017, and they enlisted some of the world’s biggest telescopes to help out. The researchers used half a dozen radio telescopes, including the ALMA telescope in Chile and the James Clerk Maxwell telescope in Hawaii, to stare at Sagittarius A* over the past two years.
And while a picture of the black hole itself is impossible, the ESO astronomers were really aiming at the next best thing: the event horizon, the border of the black hole beyond which not even light can escape. At the event horizon, gravity is so strong that light will orbit the black hole like planets orbit stars, and our telescopes should be able to pick that up.
But even with multiple telescopes pointing at Sagittarius A* for the better part of two years, imaging a black hole is not easy. The event horizon of a black hole is one of the most volatile places in the universe, and any black hole worth the name is going to be surrounded by immense amounts of dust, gas, and other stars. These are all obstacles to our telescopes, and only sheer ingenuity on the part of the ESO’s astronomers will allow us to pierce that veil.
Next week, we’ll finally get to experience the first results from this mission. There’s no way to know what to expect, although of course, everyone is hoping for a really good black hole photo. Regardless of the details, however, next Wednesday we’ll almost certainly be seeing something no human has ever seen before.