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astronomical object with such a strong gravitational attraction that light cannot escape it
(NASA) – A black hole is an astronomical object with such a strong gravitational attraction that nothing, not even light, can escape it.
The “surface” of a black hole, called its event horizon, defines the boundary where the speed required to escape exceeds the speed of light, which is the speed limit of the cosmos. Matter and radiation fall, but they can’t get out.
Two major classes of black holes have been widely observed. Stellar-mass black holes with a mass three to dozen times that of the Sun are scattered throughout our galaxy, the Milky Way, while supermassive monsters weighing 100,000 to billions of solar masses are found in the centers of most large ones. galaxies, including ours.
Astronomers have long suspected an intermediate class called intermediate-mass black holes, weighing between 100 and more than 10,000 solar masses.
While a handful of candidates have been identified with indirect evidence, the most compelling example to date came on May 21, 2019, when the National Science Foundation’s Laser Interferometer Gravitational-wave Observatory (LIGO), based in Livingston, Louisiana, and Hanford, Washington. , detected gravitational waves from a merger of two stellar-mass black holes. This event, dubbed GW190521, resulted in a black hole weighing 142 suns.
A stellar-mass black hole forms when a star with more than 20 solar masses runs out of nuclear fuel in its core and collapses under its own weight.
The collapse triggers a supernova explosion that wipes out the outer layers of the star. But if the shattered core contains more than about three times the mass of the Sun, no known force can stop its collapse into a black hole. The origin of supermassive black holes is poorly understood, but we do know that they exist from the earliest days of a galaxy’s life.
Once born, black holes can grow by accumulating matter falling into them, including gas ripped from nearby stars and even other black holes.
In 2019, astronomers using the Event Horizon Telescope (EHT), an international collaboration that networked eight terrestrial radio telescopes into a single Earth-sized dish, captured an image of a black hole for the first time. . It appears as a dark circle outlined by an orbiting disk of hot, incandescent matter.
The supermassive black hole is located in the heart of a galaxy called M87, located about 55 million light years away, and weighs more than 6 billion solar masses. Its event horizon extends so far that it can encompass much of our solar system far beyond the planets.
Another major discovery related to black holes occurred in 2015 when scientists first detected gravitational waves, ripples in the fabric of spacetime predicted a century earlier by Albert Einstein’s theory of general relativity. LIGO detected waves from an event called GW150914, in which two orbiting black holes spiraled into each other and merged 1.3 billion years ago. Since then, LIGO and other structures have observed numerous black hole mergers through the gravitational waves they produce.
These are new and exciting methods, but astronomers have been studying black holes through the various forms of light they have been emitting for decades. Although light cannot escape a black hole’s event horizon, the enormous tidal forces in its vicinity cause nearby matter to heat up to millions of degrees and emit radio waves and X-rays. Some of the material in orbit even closer to the event horizon it can be thrown out, forming jets of particles moving near the speed of light that emit radio, X-rays and gamma rays. Jets from supermassive black holes can extend into space for hundreds of thousands of light years.
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