Priyamvad Natarajan, a theoretical astrophysicist at Yale University, said that one or two of these ancient giants can be considered monsters. But so far, astronomers have discovered more than 100 supermassive black holes, which existed for 950 million years before the birth of the universe. "There are too many of them to be freaks now." "You have to have a natural explanation for how these things happen," she said.
The usual assumption is that these black holes are either unexpectedly large at birth or grow very fast. But recent discoveries even challenge these theories and may force astronomers to rethink how these black holes grow.
In the modern universe, black holes are usually formed by massive stars, which collapse at the end of their lives under the action of their own gravity. They usually start with a solar mass less than 100 and grow by merging with another black hole or absorbing gas from the environment.
These gases are usually organized into a disk and spiral into the black hole. Friction heats the disk to a white-hot temperature and produces bright light for billions of years. These gas-eating black holes are called quasars. The faster a quasar swallows, the brighter its disk becomes.
However, the luminescence of gas also limits the growth of black holes: bright disc photons drive away fresh matter. This sets a physical limit for the growth rate of a given mass black hole. Astronomers use a term called sexual dington limit to describe the rate of black hole swallowing and measure the actual brightness of a black hole. If it swallows faster, it will have a how bright.
However, the luminescence of gas also limits the growth of black holes: bright disc photons drive away fresh matter. This sets a physical limit for the growth rate of a given mass black hole. Astronomers use a term called sexual dington limit to describe the rate of black hole swallowing and measure the actual brightness of a black hole. If it swallows faster, it will have a how bright.
Beyond scientists' understanding, why did the black hole become so big?
A picky eater.
Astronomers only measured the Eddington limit of about 20 supermassive black holes in the early universe. Most seem to be devouring their limits at one-tenth the speed of quasars in the universe today. These violent swallowing speeds still seem to contradict the supermassive black hole: a black hole with the mass of 100 times that of the sun should take 800 million years to accumulate the mass of1000 billion of the sun at this limit, even considering its faster swallowing speed during its growth. This 800 million years does not include the time when black holes first formed.
But Myungshin Im, a physicist at Seoul National University in South Korea, and his colleagues worry that previous observations have missed some picky eaters because fast eaters are smarter and easier to find. If some early massive black holes were lazy predators, their oversize would become even more confusing-some theories about how they grew might be ruled out.
Therefore, in a survey conducted by the Las campana Observatory in Chile in September 20 15, the team deliberately searched for dark and distant quasars.
The researchers found that IMSJ 204+0 1 12 is a black hole with a mass of10 billion sun, which restricts eating at a speed of one tenth, since the birth of the universe about 940 million years ago. But the team said on February 9 that black holes will not fully mature until the universe reaches 8 billion years old.
Beyond scientists' understanding, why did the black hole become so big?
"We first proved the existence of quasars with low Eddington limit in the early universe," Imm said.
IMSJ 204+0 1 12 is the slowest quasar discovered so far, but it is not the only one. In June last year,165438+1October, Chiara Mazzucchelli, a physicist at the Max Planck Institute for Astronomy in Germany, and his colleagues published a report in the Journal of Astrophysics, saying that when 1 1 huge supermassive black holes existed, the universe was less than 8 years old.
The team said that the average mass of these quasars is about 65.438+0.62 billion solar mass, but their swallowing speed is limited to about 40%. Strangely, HSC J 1205-0000, the largest black hole in the stellar nebula, has the lowest feeding rate: its mass is 4.7 billion solar mass, but it only consumes 6% of its limit.
It would be strange to find supermassive black holes in the early universe, but these picky black holes are more difficult to explain.
Astronomers hope that observing black holes at an earlier time will help to find "seed" black holes that may grow into huge black holes. If some black holes are very big from the beginning, with the mass between 1 1,000 and 1 1,000 suns, they may become bigger, either merging with each other or reaching the Eddington limit.