英语听力：黑洞吞噬—18

Here then is the strange paradox of black holes: the defeating black hole is anything but black. Just how greedy and bright a black hole can get is revealed by an aptly very ordinary looking galaxy called Cygnus A, some 650 million light years away.

If we look at it with visible light, we see that the inner parts of that galaxy, maybe a few 10 thousand light years across, is kind of ordinary. There are stars. There’s gas. There’s dust. It’s a sort of indiscriminately messy place, but it's not that special.

Now if we look in different wavelengths, for example, in radio waves, we see something completely different. Cygnus A transforms into something else entirely. What we see is no longer the galaxy with its stars, but instead, we see an extreme structure spread across intergalactic space. And the structure is enormous. It stretches 500,000 light years across. And it consists of these enormous lobes of brightness, linked together by what looks like a thread of light leading to a tiny bright point at the very centre of the Cygnus A galaxy. The structure is enormously luminous and there's also a huge amount of energy just in the particles themselves because they've been accelerated close to the speed of light. So if you add up all the energy in this great structure, it's probably at least a trillion times the amount of energy that our sun puts out on a regular basis.