Scientists have long dreamed of observing black holes in action, predicting how they behave and even witnessing them collide with one another. These cosmic crashes have the potential to unlock mysteries such as the origins of our universe and how black holes form. But do they also pose danger to Earth?
The answer is no. Despite their reputation as cosmic vacuum cleaners that devour anything within their reach, black holes can only capture objects very close to them. That’s why our planet is safe from being sucked into one. However, that doesn’t mean that black holes don’t affect our lives in some way.
Black holes generate lots of heat, which they release in the form of radio waves. This energy is emitted from a black hole’s event horizon and can be detected with radio telescopes in space. It’s this radiation that has given rise to a phenomenon known as the black hole jet, which shoots out a burst of light from the region surrounding the event horizon.
Astronomers have found that these jets can produce powerful gamma-ray bursts and even influence the growth of nearby stars. But there’s no reason to fear them if you’re located far enough away. The nearest stellar-mass black hole to Earth, a celestial body called V616 Mon (pictured above), is 1,500 light years away. That’s a good distance from our planet, and it would take hundreds of thousands of years for the star to orbit the black hole and pass close enough for us to feel its effects.
The closer you get to a black hole, the more its gravity will affect you. But the distance at which you can feel that effect is determined by the mass of the black hole.
At its smallest, a black hole has the mass of about a billion Suns. As that mass increases, the force of its gravity will increase, too. At a certain point, its gravitational force will be so strong that nothing can escape. This point is called the event horizon, and it’s the boundary from which no light or matter can cross.
As a black hole expands, it can no longer contain the same amount of mass, and its event horizon moves inward. That’s why a black hole that consumes a star or other object will grow in size.
But what happens if that star or other body is too big for the event horizon to swallow? The rest of the matter will fall into a region surrounding it that’s called the accretion disk, which is super-hot and extremely dense. It will rip that matter apart and then spin rapidly, creating a donut-shaped structure that emits high-energy radiation.