Deep Dive
Shownotes Transcript
From the brains behind Brains On, this is the Moment of Um. Answering those questions that make you go, um. Moment of Um comes to you from APM Studios. I'm Molly Bloom, and I'm letting my dog Honeybee out for a potty break. Oh dear, where is it? Honeybee, where did you go poopies? Show mama.
Oh, hi. My pup honeybee just made a number two somewhere in my backyard and I need to scoop it up now so I don't step in it later. But it's getting dark out and poo is dark. Oh, there it is. Oh, no, that's just a rock. Trying to spot a tiny dark turd in a huge dark yard is like, well, probably trying to spot a black hole in the vastness of space.
Speaking of, I've always wondered: if black holes are places in the universe that are so dense no light can escape, how can we ever spot them? Sure, scientists believed they existed because Einstein's theories say they should exist, but for a long time, no one had proof they were real. And if they are black against a black universe, how did we ever discover the first one?
Ali wondered this too, and asked us how scientists found the first black hole. Let's get a space scientist to weigh in. The first black hole was discovered almost by accident. My name is Varujan Ghorjian, and I'm at NASA's Jet Propulsion Laboratory. A black hole is an object that has such strong gravity that even light can't escape.
Anything that has gravity that keeps things close to it is that it has mass. And the closer you are to something that has a lot of mass, then the harder it is to get away from it. For a black hole, there's a lot of mass, but it's also really compact, which means you can get really close to all that mass, which means you can really feel all the intense gravity of that mass. And it gets to the point where light can't escape. The theory of black holes is based on Einstein's theory of gravity, which describes how gravity works.
And people figured out that it made it possible for something to be so compact and have so much mass in it and so much gravity so that light couldn't even escape. But people started looking up in the sky and using different wavelengths of light. In this case, they were looking at X-rays, which aren't the wavelengths that our eyes can see. And they saw some bright X-ray sources in the sky.
And it turned out that one of these X-ray sources in the constellation of Cygnus, the Swan, was actually coming from a binary star. Two stars that are orbiting each other. And they could see one star, like our eyes can see, but they couldn't see what the other thing was. But it also had a lot of mass and it was emitting a lot of X-rays.
That means there was something very hot near it. You have to be very hot to emit X-rays. And so what they found out was gas from the big star was falling into this black hole and it was falling and falling and falling. So the further you fall, the more energy you release. And it was just making this whirlpool and it was getting hotter and hotter and hotter and it was emitting X-rays.
based on the mass that it had to have, because when you have two stars orbiting each other, you can figure out the mass of each one. It turned out that it had to be beyond the mass that was predicted, that it would have to be a black hole. The first black hole was discovered in 1964, when we could send telescopes up into space that wouldn't have the interference of our atmosphere. Since then, we've discovered millions of other black holes.
Some, like Cygnus X-1, are a few times the mass of our sun, but many are millions to billions of times the mass of our sun. But they're very, very far away. The best way we know of finding them is to look for that gas that's falling into it that heats up right before it goes into the black hole and is never heard from again. Um, uh,
Whoa, what an ingenious way to spot a black hole. Since it doesn't emit light, you can't see black holes with your eyes, so scientists looked for something else. The first one was found when scientists noticed something really heavy in space was giving off a bunch of x-rays. The black hole itself wasn't shooting out x-rays, but as stuff fell into it, x-rays were released. So it's like spotting the outline of the black hole.
Speaking of outlines, I think I see the outline of that disappeared dookie. Gotcha! Oh, sorry, Mr. Frog. It's dark and I thought you were something else. My bad. If you like this episode, take a second to subscribe to Moment of Om wherever you listen to podcasts. And if you like space, check out the Forever Ago podcast where we have a whole episode all about a secret training program that paved the way for female astronauts.
Want to see our shows come to life? Head to YouTube where we've got some awesome animated Brains On episodes. Search Brains On Universe on YouTube and subscribe. If you have a question, we would love to help you answer it. Drop us a line by going to brainson.org slash contact. See you next time and the next day and every weekday. Until then, um...
Oh, fiddlesticks, I give up. I'll get that doggie due tomorrow. There it is.