Halloween is a time haunted by ghosts, goblins and vampires, but there’s nothing in the universe that is more terrifying than a black hole.
Black holes – regions in space where gravity is so strong that nothing can escape – are a hot topic these days. Half of the 2020 Nobel Prize in Physics was awarded to Roger Penrose because his mathematical work showed that black holes are an inevitable consequence of Einstein’s theory of gravity. Andrea Ghez and Reinhard Genzel share the other half for pointing out that a giant black hole is at the center of our galaxy.
Black holes are scary for three reasons. If you fall into a leftover black hole when a star dies, you will be torn apart. In addition, the giant black holes seen in the centers of all galaxies experience insatiable cravings. And the black hole is where the laws of physics are undone.
I’ve been studying black holes for over 30 years. In particular, I have focused on supermassive black holes lurking in the centers of galaxies. Most of the time they are inactive, but when they are active and ingest the stars and gas, the area near the black hole can extend beyond the entire galaxy that contains them. Galaxies where black holes are active are called quasars. With all we have learned about black holes over the past few decades, there are still a lot of mysteries to solve.
Dead by a black hole
Black holes are thought to form when a large star dies. After the star’s nuclear fuel is exhausted, its core collapses to the densest state of matter imaginable, a hundred times denser than the atomic nucleus. It is so dense that the protons, neutrons and electrons are no longer discrete particles. Because black holes are dark in color, they are found when they orbit a normal star. The properties of an ordinary star allow astronomers to infer the properties of its dark companion, a black hole.
The first confirmed black hole is Cygnus X-1, the brightest source of X-rays in the constellation Cygnus. Since then, about 50 black holes have been discovered in systems where a normal star orbits a black hole. They are the closest examples of about 10 million people thought to be scattered in the Milky Way.
A black hole is a tomb of matter; nothing can escape them, not even light. The fate of anyone who falls into a black hole will be a painful “birth”, an idea popularized by Stephen Hawking in his book A Brief History of Time. During spaghettification, the black hole’s intense gravity will pull you away, separating your bones, muscles, tendons and even molecules. As the poet Dante described the words on the gates of hell in his poem Divine Comedy: Give up hope, all who enter here.
A hungry beast in every galaxy
Over the past 30 years, Hubble Space Telescope observations have shown that all galaxies have black holes at their centers. Larger galaxies have larger black holes.
Nature knows how to create black holes on a range of staggering masses, from corpses of stars several times the mass of the Sun to monsters tens of billions of times. It’s like the difference between an apple and the Great Pyramid of Giza.
Just last year, astronomers published the first image of a black hole and its event horizon, a monster with a mass of 7 billion suns in the center of the elliptical galaxy M87.
It is a thousand times larger than the black hole in our galaxy, for which its discoverers won this year’s Nobel Prize. These black holes are dark most of the time, but as their gravity pulls the nearby stars and gas, they explode into intense activity and pump out large amounts of radiation. Huge black holes are dangerous in two ways. If you get too close, the enormous gravity will pull you in. And if they are in active quasar mode, you will be blown away by high-energy radiation.
How bright is the standard? Imagine flying over a big city like Los Angeles at night. About 100 million of the light from cars, houses and city streets corresponds to the stars in the galaxy. Likewise, the black hole in its active state is like a light source 1 inch in diameter in downtown LA that is hundreds or thousands brighter than the city. Quasars are the brightest objects in the universe.
Supermassive black holes are very strange
The largest black hole discovered so far is 40 billion times the mass of the Sun, or 20 times the size of the solar system. While the outer planets in our solar system orbit once in 250 years, this much heavier object rotates every three months. Its outer edge moves at half the speed of light. Like all black holes, giant holes are shielded from view by the event horizon. At their center is a singularity, a point in space where density is infinite. We cannot understand the inside of a black hole because the laws of physics are broken. Time freezes at the event horizon and gravity becomes limitless at the singularity.
The good news about large black holes is that you can survive a fall. Although their gravity is stronger, the stretching force is weaker than the impact of a small black hole and it will not kill you. The bad news is that the event horizon marks the edge of the abyss. Nothing can escape from within the event horizon, so you cannot escape or report on your experience.[[[[Deep knowledge, everyday. Sign up for The Conversation newsletter.]
According to Stephen Hawking, black holes are slowly evaporating. In the distant future of the universe, long after all the stars have died and the galaxies were narrowed in view by the accelerating expansion of the universe, the black hole would be the last remaining object. .
The largest black holes will take an unimaginable number of years to evaporate, estimated to be 10 to 100, or 10 with 100 zeros after it. The most terrifying objects in the universe are almost eternal.
This article was republished from The Conversation, a non-profit news site dedicated to sharing ideas from academic experts. It was written by: Chris Impey, University of Arizona.
Chris Impey does not work for, advise, own stock or receive funding from any company or organization that may benefit from this article and does not disclose any relevant affiliates beyond the academic appointment. their.