Black holes are one of the most mysterious cosmic phenomena, despite how much we are still learning about them. Although considered a mathematical possibility for many years, the first black hole was recently discovered Cygnus X-1 in 1971.
We now know that black holes are common in the universe. One Sagittarius A* is located in the center of our galaxy, the Milky Way. According to NASA, most galaxies of similar size have monstrous black holes at their centers. Sagittarius A* has about 4 million times more mass than the Sun.
Black holes aren’t actually holes. They are so called because their matter is so dense that not even light can escape their gravity. In an image of one, you see a ring of light circling a black hole like a donut. The center of the donut is the black hole. Just like stars and planets, black holes also rotate. The ring of light and matter surrounding a black hole is called the accretion disk, and it becomes hot and bright as it spins rapidly around the black hole.
Don’t believe the hype about a scary black hole eating everything it can attract. If our sun were replaced by a black hole of the same mass, our solar system would orbit the Earth the same way it does now, but it would be a lot colder.
We don’t know what matter looks like in a black hole. We do know that any matter that exceeds the Event Horizon, the edge of a black hole, would eventually undergo what is called spaghettification. It’s exactly what it sounds like: matter would be compressed and stretched, essentially turning into a noodle.
Black holes are not ‘cosmic vacuum cleaners’ explains NASA. Although their gravity is incredibly strong, celestial bodies can orbit black holes just like other stars. While an object can be sucked in if its orbit brings it too close, from further away gravity behaves exactly as we are used to in our own solar system. We now know that some black holes are formed by the death and collapse of stars.
“Black holes are not bad. You can orbit a black hole just like you can orbit any other star or other massive object,” said Varoujan Gorjan, a NASA research astronomer in an agency statement on the subject.
That said, stars orbiting black holes can be destroyed by the black hole’s supermassive gravity. The black hole’s gravity can flatten and tear apart the star that is orbiting too close in what is called an a tidal disturbance event. Some of the star’s material can be sucked into the black hole as the star itself continues its orbit around Earth. If there is any left, the process repeats as the star continues to orbit the black hole.
Black holes can be identified using a variety of imaging techniques, including X-rays and ultraviolet wavelengths. Gravitational wave observatories have also been able to detect the ripples in space-time that are created when two black holes merge. Scientists are still trying to answer the question of how the enormous black holes at the centers of galaxies formed there in the first place.
Finding black holes requires some creativity. One way scientists have located black holes is by looking at fast orbits of stars around something we can’t see. The only way to explain fast-moving stars orbiting a central invisible object is for that object to be a black hole with enough gravity to hold the stars in place. Scientists discovered Cygnus X-1 by recognizing its accretion disk, which was created by stealing material from a nearby companion star. The overheated accretion disk was visible on X-rays.
While we don’t have to worry that the black hole at the center of our galaxy will expand and swallow everything, we can track rogue black holes as they move through the universe. When it launches in 2027, the Roman Space Telescope Nancy Grace will find black holes by looking for the telltale signs of starlight being distorted on its way to us by a black hole between the telescope and the distant star. The warped light will be an indication that a black hole is present.
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