Black holes are scary for three reasons. If you fall into the black hole left behind when a star dies, it will be torn apart. And the huge black hole visible at the center of all galaxies has an insatiable appetite. Black holes are places where the laws of physics are obscured.
Hungry monsters in every galaxy
Nature knows how to create black holes in an astonishing range of masses, from stellar corpses several times the mass of the Sun to monsters tens of billions of times larger. It’s like the difference between an apple and the Great Pyramid of Giza.
It is more than a thousand times larger than the black hole in our galaxy, and its discoverer received the Nobel Prize this year. These black holes are mostly dark, but when their gravity pulls on nearby stars and gas, they erupt in intense activity and pump out massive amounts of radiation. Supermassive black holes are dangerous in two ways. If you get too close, sheer gravity will suck you in. And if it is in an active quasar phase, it will be exposed to high-energy radiation.
How bright are the quasars? Imagine you are hovering over a big city like Los Angeles at night. Nearly 100 million lights from cars, houses and city streets correspond to the stars in the galaxy. In this analogy, a black hole in its active state is like a one-inch light source in downtown Los Angeles that outperforms the city by a factor of hundreds or thousands. Quasars are the brightest objects in the universe.
Supermassive black holes are weird
The good news about big black holes is that you can survive falling into one. Even though its gravity is stronger, its expansion force is weaker than a small black hole and it won’t kill you. The bad news is that the event horizon marks the edge of the cliff. Nothing escapes from within the event horizon, so you can’t escape or report your experience.
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Chris Embi He is Distinguished University Professor of Astronomy at the University of Arizona.
