史上首張黑洞照片是怎樣拍到的？
發佈於: 5年前
What you are seeing is the first-ever image of a black hole. Maybe it doesn’t look spectacular at first. But consider this: Black holes by their very nature are invisible. Because their gravitational pull is so strong that not even light can escape them. So, for many years, astronomers thought that an image like this was impossible. How do you take a picture of something that does not emit light? Well, it starts with a small team of innovators, and ends with a telescope that’s unlike anything the world has ever seen.
Now, despite major advances in telescope technology, there is no single telescope on Earth that can take a picture of a black hole. They’re all too small. So, astronomers innovated. If one telescope couldn’t do the job, then perhaps 8 would – and they were right. They used 8 radio telescopes stationed at different points across the world, and kept them all in synch with powerful atomic clocks. They call the effort the Event Horizon Telescope.
This series of telescopes, combined, has about the same capabilities as a telescope as large as our entire planet. And for the first time in history, it has shown us what a black hole around 55 million light years away looks like.
This black hole is actually a supermassive black hole. It’s about 6.5 billion times as massive as our Sun – that’s enormous even compared to other supermassive black holes and lives in the center of the Messier 87 galaxy. And as far as experts can tell, it looks exactly like what Einstein’s general theory of relativity predicted. Here’s a simulation of what the Event Horizon Team thought the black hole would look like.
And here’s the real image. The light you see here is what’s called the accretion disk. It’s a disk of light that forms around the black hole when a star travels too close and is broken apart in the process. But the most important part of this photo is where there is no light – that dark circle in the center, which measures 25 billion miles across.
That right there is proof that black holes look and behave how astronomers thought. More specifically, that they actually have an edge. It’s a place of no return, which astronomers call the event horizon. Once you cross the event horizon, the black hole’s gravity is so strong that you cannot escape. Not you, nor the fastest spacecraft, and not even the fastest thing in the universe: light. That’s why the edge and everything beyond it are black. Trapped inside the black hole’s gravitational grip. And this image may be just the beginning.
The Event Horizons Telescope team has also turned its sights on another black hole – one that is closer to home, called Sagittarius A*. It’s the supermassive black hole at the center of our own galaxy, the Milky Way, about 25,000 light years away. But it’s significantly smaller than the one in Messier 87. So, it will probably be more difficult to image. And since it took astronomers two years to combine and analyze data for this first image, it may be a while before we see what other black holes look like.