What does a black hole look like? | Science News


Every image you’ve seen of a black hole, including this one, is a fantasy. A genuine picture of a black hole doesn’t exist, but soon, that’s going to change. Black holes in their own don’t look like very much. They don’t reflect light because any light that falls into them can never escape. And they don’t emit any light that we can detect Those aren’t the only reasons black holes are hard to photograph. Even though they’re really, really massive — they can be millions or billions of times the mass of the Sun — they don’t take up that much space on the sky. They’ve compressed all that mass into a really tiny, little space. The closest big black hole to Earth is at the centre of the Milky Way, which is 26,000 light-years away from us. And so in order to be able to see something of that size, we need a telescope that has a resolution that is powerful enough that it could see a doughnut on the surface of the moon. The black hole illustrations we’re all familiar with aren’t complete lies. Plenty of data suggest that black holes exist. Some even shoot jets into space that we can see and spaghettify stars that get too close. The best evidence for these behemoths is their entourage. They wrap huge amounts of gas and like charged plasma around them. And as that stuff is trying to fall into the black hole, it can’t all go in at once, so it orbits super, super, super fast. And the friction in that fast orbiting heats it white-hot. Most illustrations focus on the accretion disk, but soon, we could be looking at the real deal — thanks to the Event Horizon Telescope or the EHT. The EHT is trying to take the first picture of the black hole at the center of the Milky Way. It’s called Sagittarius A* or Sgr A* for short. And the team expects to produce results later this year. What it’s actually doing is taking a picture of the shadow of the black hole on the stuff behind it. By stuff, she means the glowing gas and plasma in the accretion disk. The black hole’s shadow should create a silhouette on the disk that outlines the point of no-return — the event horizon. Taking such a picture would require a really, really big telescope. The EHT uses a lot of smaller radio telescopes instead. They work together using a technique called very long baseline interferometry and what that does is it makes those telescopes kind of act like one giant telescope. Scientists analyzing the data can see how the light waves detected by each telescope line up with each other to figure out what’s light from the edge of the black hole and what’s noise. The EHT’s picture will most likely look like a ring, created by the black hole’s event horizon blocking out light from behind. That first image, though perhaps grainy, will give us an up-close look at the accretion disk plus two key bits of information: the size and shape of the black hole’s shadow. And then that will be enough to answer a lot of interesting astrophysical questions about how black holes work, how event horizons work and what is going on there. There the big unanswered questions include: How exactly do accretion discs form and feed black holes? Where do black hole jets originate? And the oldie but always a goodie, was Einstein right? His general theory of relativity predicted that event horizons could conceal tiny, massive objects like black holes. The shape of this image that we see is something that you can predict using general relativity. If the shape of the image of the black hole looks different than we expect, that would mean that something’s wrong that we don’t fully understand about general relativity. Taking a picture of a black hole will mark the most extreme test of general relativity yet. This test of relativity also has implications for the physics theory of it deals with very small objects, quantum mechanics. The two of them don’t play well together. We don’t understand how gravity works on sort of quantum levels. And if we see something that differs from our expectation in this picture of the black hole, that can help point us to one of many theories that try to reconcile quantum mechanics and general relativity. It’s also just cool. Whether it’s a pale blue dot or a pristine portrait of Pluto, seeing has always offered us a new perspective on the universe. Humans are very visual, and so we love having images. And I think having an actual picture of black hole is just going to blow people’s minds. Am I going to like break continuity if I roll up my sleeves? And I’m going to start this one over. This is hard. I was just watching the Great British Baking Show last night. Ummm. They wear the same clothes two days in a row. We’ll go there, yeah. I feel like it’s wrong. Sorry, yeah, you can cut that. So, don’t roll up your sleeves then. Something like that. [Laughs] [Laughing]