European Space Agency:
Black holes are the strangest objects in the Universe. A black hole does not have a surface, like a planet or star. Instead, it is a region of space where matter has collapsed in on itself. This catastrophic collapse results in a huge amount of mass being concentrated in an incredibly small area. The gravitational pull of this region is so great that nothing can escape – not even light.
Although black holes cannot be seen, we know they exist from the way they affect nearby dust, stars and galaxies. Many of them are surrounded by discs of material. As the discs swirl around them like a whirlpool, they become extremely hot and give off X-rays.
Black holes come in many different sizes. Many of them are only a few times more massive than the Sun. These 'stellar-mass' black holes form when a heavyweight star, about 10 times heavier than the Sun, ends its life in a supernova explosion. What is left of the star – still several solar masses - collapses into an area only a few kilometres across.
Most galaxies, including the Milky Way, have supermassive black holes at their centres. These may be millions or billions of times heavier than our Sun. Supermassive black holes also power active galaxies and ancient galaxies known as quasars. Quasars may be hundreds of times brighter than even the largest ordinary galaxies.
Objects that fall into black holes are literally stretched to breaking point. An astronaut who ventured too close and was sucked into a black hole would be pulled apart by the overpowering gravity.
Although black holes cannot be seen, we know they exist from the way they affect nearby dust, stars and galaxies. Many of them are surrounded by discs of material. As the discs swirl around them like a whirlpool, they become extremely hot and give off X-rays.
Black holes come in many different sizes. Many of them are only a few times more massive than the Sun. These 'stellar-mass' black holes form when a heavyweight star, about 10 times heavier than the Sun, ends its life in a supernova explosion. What is left of the star – still several solar masses - collapses into an area only a few kilometres across.
Most galaxies, including the Milky Way, have supermassive black holes at their centres. These may be millions or billions of times heavier than our Sun. Supermassive black holes also power active galaxies and ancient galaxies known as quasars. Quasars may be hundreds of times brighter than even the largest ordinary galaxies.
Objects that fall into black holes are literally stretched to breaking point. An astronaut who ventured too close and was sucked into a black hole would be pulled apart by the overpowering gravity.
National Geographic Kids:
At the center of most galaxies is one of the strangest and deadliest things in the universe: a black hole.
Most black holes, regardless of their size, are born when a giant star runs out of energy. The star implodes, and its center collapses under its own weight. This causes an explosion called a supernova. The giant star is eventually squashed into a supersmall dot you can’t see.
A black hole’s gravity, or attractive force, is so strong that it pulls in anything that gets too close. It can even swallow entire stars. Nothing can move fast enough to escape a black hole’s gravity. This includes light, the fastest thing in the universe. That’s why we can’t see black holes in space—they've gobbled up all the light. Though astronomers can’t see black holes, they know they’re there by the effect they have on objects that get too close.
Two types of black holes exist. Supermassive black holes are the largest type of black hole. They’re up to one million times more massive than our sun. This is the kind of black hole that’s at the center of our galaxy, the Milky Way; it’s called Sagittarius A*. (A* is scientist-code for “A-star.”) The most common type of black holes, stellar black holes, are only up to 20 times more massive than our sun.
The intense gravity near a black hole makes time behave in strange ways. If an astronaut left his spacecraft to explore a black hole up close, he’d see the hands on his watch ticking at normal speed. But if anyone back on the spacecraft could observe the astronaut’s watch from far away, they’d see its hands slow down as the spacewalker got closer to the black hole. When the spacewalker returned to the spaceship after an hour-long spacewalk, years would have passed for those aboard the spacecraft.
Someday humans might be able to use black holes to time travel forward. An astronaut could take a short trip near a black hole and return to Earth after years, decades, or even centuries had passed there. A black hole time machine could allow an astronaut to find out what the world will be like in the future. But going back in time? That’s a different challenge altogether!
DID YOU KNOW?
• Thousands of potential black holes have been discovered, but NASA thinks there could be more than a billion of them in space.
• Black holes don't live forever. They slowly evaporate over time, returning their energy to the universe.
• In 2015 two black holes crashed into each other more than a billion light-years from Earth. (A light-year is the distance light travels in one year.) They weren’t destroyed though—they just merged to create a bigger black hole.
Most black holes, regardless of their size, are born when a giant star runs out of energy. The star implodes, and its center collapses under its own weight. This causes an explosion called a supernova. The giant star is eventually squashed into a supersmall dot you can’t see.
A black hole’s gravity, or attractive force, is so strong that it pulls in anything that gets too close. It can even swallow entire stars. Nothing can move fast enough to escape a black hole’s gravity. This includes light, the fastest thing in the universe. That’s why we can’t see black holes in space—they've gobbled up all the light. Though astronomers can’t see black holes, they know they’re there by the effect they have on objects that get too close.
Two types of black holes exist. Supermassive black holes are the largest type of black hole. They’re up to one million times more massive than our sun. This is the kind of black hole that’s at the center of our galaxy, the Milky Way; it’s called Sagittarius A*. (A* is scientist-code for “A-star.”) The most common type of black holes, stellar black holes, are only up to 20 times more massive than our sun.
The intense gravity near a black hole makes time behave in strange ways. If an astronaut left his spacecraft to explore a black hole up close, he’d see the hands on his watch ticking at normal speed. But if anyone back on the spacecraft could observe the astronaut’s watch from far away, they’d see its hands slow down as the spacewalker got closer to the black hole. When the spacewalker returned to the spaceship after an hour-long spacewalk, years would have passed for those aboard the spacecraft.
Someday humans might be able to use black holes to time travel forward. An astronaut could take a short trip near a black hole and return to Earth after years, decades, or even centuries had passed there. A black hole time machine could allow an astronaut to find out what the world will be like in the future. But going back in time? That’s a different challenge altogether!
DID YOU KNOW?
• Thousands of potential black holes have been discovered, but NASA thinks there could be more than a billion of them in space.
• Black holes don't live forever. They slowly evaporate over time, returning their energy to the universe.
• In 2015 two black holes crashed into each other more than a billion light-years from Earth. (A light-year is the distance light travels in one year.) They weren’t destroyed though—they just merged to create a bigger black hole.
Ducksters.com:
What is a black hole? Black holes are one of the most mysterious and powerful forces in the universe. A black hole is where gravity has become so strong that nothing around it can escape, not even light. The mass of a black hole is so compact, or dense, that the force of gravity is too strong for even light to escape. Can we see them? Black holes are truly invisible. We can't actually see black holes because they don't reflect light. Scientists know they exist by observing light and objects around black holes. Strange things happen around black holes to do with quantum physics and space time. This makes them a popular subject of science fiction stories even though they are very real.
How are they formed? Black holes are formed when giant stars explode at the end of their lifecycle. This explosion is called a supernova. If the star has enough mass, it will collapse on itself down to a very small size. Due to its small size and enormous mass, the gravity will be so strong it will absorb light and become a black hole. Black holes can grow incredibly huge as they continue to absorb light and mass around them. They can even absorb other stars. Many scientists think that there are super-massive black holes at the center of galaxies. Event Horizon There is a special boundary around a black hole called an event horizon. It is at this point that everything, even light, must go toward the black hole. There is no escape once you've crossed the event horizon!
Who discovered the black hole? The idea of the black hole was first proposed by two different scientists in the 18th century: John Michell and Pierre-Simon Laplace. In 1967, a physicist named John Archibald Wheeler came up with the term "black hole". Fun Facts about black holes Black holes can have the mass of several million suns. They don't live forever, but slowly evaporate returning their energy to the universe. The center of a black hole, where all its mass resides, is a point called a singularity. Black holes differ from each other in mass and their spin. Other than that, they are all very similar. The black holes we know about tend to fit into two size categories: "stellar" size are around the mass of one star while "supermassive" are the mass of several millions of stars. The big ones are located at the centers of large galaxies.
How are they formed? Black holes are formed when giant stars explode at the end of their lifecycle. This explosion is called a supernova. If the star has enough mass, it will collapse on itself down to a very small size. Due to its small size and enormous mass, the gravity will be so strong it will absorb light and become a black hole. Black holes can grow incredibly huge as they continue to absorb light and mass around them. They can even absorb other stars. Many scientists think that there are super-massive black holes at the center of galaxies. Event Horizon There is a special boundary around a black hole called an event horizon. It is at this point that everything, even light, must go toward the black hole. There is no escape once you've crossed the event horizon!
Who discovered the black hole? The idea of the black hole was first proposed by two different scientists in the 18th century: John Michell and Pierre-Simon Laplace. In 1967, a physicist named John Archibald Wheeler came up with the term "black hole". Fun Facts about black holes Black holes can have the mass of several million suns. They don't live forever, but slowly evaporate returning their energy to the universe. The center of a black hole, where all its mass resides, is a point called a singularity. Black holes differ from each other in mass and their spin. Other than that, they are all very similar. The black holes we know about tend to fit into two size categories: "stellar" size are around the mass of one star while "supermassive" are the mass of several millions of stars. The big ones are located at the centers of large galaxies.
Curiouskids.com:
Black holes can form when a massive star dies. Stars have a lot of mass which means there is a lot of gravity pulling in on the star. Gravity is the same force that keeps you on Earth so you don’t float into space!
These stars are also made up of very hot gas which lets off a lot of heat. This creates a force which pushes on the star from the inside out.
Normally the pull from gravity and the push from the heat balance each other out. But, as the star gets older, it burns up all of the fuel and there isn’t anything left to push out anymore. Now gravity takes over and all of the mass of the star falls in on itself into a single point. This is what we call a black hole.
You will never be able to escape a black holeBecause black holes are made up of a lot of mass squished into a very small area of space (in science speak we say black holes are very dense) they create a lot of gravity. This pulls in anything that gets too close.
The pull they create is so strong that if you get too close to a black hole – even if you are travelling away from it at the fastest speed it is possible to go – you will never be able escape. This is what astronomers call the event horizon. Once you are inside the event horizon of the black hole you will never be able to leave.
Black holes were given that name because if you were to take a picture of one, you wouldn’t be able to see anything. No light would be able to escape the black hole and make it to the camera (and after all, all a camera does is record light). You would just see a picture of the universe with a dark circle around where the black hole sits.
Sadly, it is really hard to get a camera good enough to take pictures like that. Instead, astronomers study black holes by looking at the stuff that is getting sucked into the black holes, before it gets too close and goes past the event horizon. There is no way for us to see what happens once you get inside.
So, where do they lead to?Now to the big question: what happens once you go into a black hole and past the event horizon? The answer is that we don’t actually know yet. We are still trying to figure that out!
One idea is that black holes form things called wormholes. You can read this Curious Kids article to find out all about wormholes.
These wormholes act as tunnels between two different parts of the space. This means that you could step into a black hole and end up in a completely different part of our universe. You might even end up in a different universe!
Astronomers have spent a lot of time trying to describe how wormholes could form and work. We won’t know for sure if that is really what happens once you go through a black hole though until we figure out a way to see it happen. Maybe one day you will become a scientist and help us find these answers. Your excellent question shows you are on the right track.
These stars are also made up of very hot gas which lets off a lot of heat. This creates a force which pushes on the star from the inside out.
Normally the pull from gravity and the push from the heat balance each other out. But, as the star gets older, it burns up all of the fuel and there isn’t anything left to push out anymore. Now gravity takes over and all of the mass of the star falls in on itself into a single point. This is what we call a black hole.
You will never be able to escape a black holeBecause black holes are made up of a lot of mass squished into a very small area of space (in science speak we say black holes are very dense) they create a lot of gravity. This pulls in anything that gets too close.
The pull they create is so strong that if you get too close to a black hole – even if you are travelling away from it at the fastest speed it is possible to go – you will never be able escape. This is what astronomers call the event horizon. Once you are inside the event horizon of the black hole you will never be able to leave.
Black holes were given that name because if you were to take a picture of one, you wouldn’t be able to see anything. No light would be able to escape the black hole and make it to the camera (and after all, all a camera does is record light). You would just see a picture of the universe with a dark circle around where the black hole sits.
Sadly, it is really hard to get a camera good enough to take pictures like that. Instead, astronomers study black holes by looking at the stuff that is getting sucked into the black holes, before it gets too close and goes past the event horizon. There is no way for us to see what happens once you get inside.
So, where do they lead to?Now to the big question: what happens once you go into a black hole and past the event horizon? The answer is that we don’t actually know yet. We are still trying to figure that out!
One idea is that black holes form things called wormholes. You can read this Curious Kids article to find out all about wormholes.
These wormholes act as tunnels between two different parts of the space. This means that you could step into a black hole and end up in a completely different part of our universe. You might even end up in a different universe!
Astronomers have spent a lot of time trying to describe how wormholes could form and work. We won’t know for sure if that is really what happens once you go through a black hole though until we figure out a way to see it happen. Maybe one day you will become a scientist and help us find these answers. Your excellent question shows you are on the right track.