Black hole existed 1.5 billion years after Big Bang
6/11/2024 6:08
At the heart of our Milky
Way galaxy lurks a supermassive black hole about four million
times the mass of the sun, called Sagittarius A*. In fact, these
objects, which increase in mass over time by eating material
that wanders too close, reside at the center of most galaxies.
But since NASA's James Webb Space Telescope came online in
2022, astronomers have been surprised to find supermassive black
holes inhabiting the early universe - earlier than they had
thought possible considering the time needed to gather such
great mass. New observations of one such primordial black hole
is offering insight into how this may have occurred - through
episodes of supercharged growth.
Black holes are extremely dense objects with gravity so
strong that not even light can escape. With their immense
gravitational pull, they grow in mass by sucking in material
such as gas, dust and stars unfortunate enough to stray nearby.
"The existence of supermassive black holes in the early
universe challenges our current models of black hole formation
and growth," said astronomer Hyewon Suh of the International
Gemini Observatory in Hawaii and the U.S. National Science
Foundation's NOIRLab, lead author of the study published in the
journal Nature Astronomy.
The new Webb observations involve a supermassive black hole
called LID-568 that existed when the cosmos was about 11% its
current age - about 1.5 billion years after the Big Bang event
13.8 billion years ago that initiated the universe. LID-568 has
a mass about 10 million times greater than the sun, so 2-1/2
times that of Sagittarius A*. The researchers have not yet
determined the mass of its home galaxy.
LID-568 was observed gaining mass at a pace faster than
previously thought possible. Webb showed that, based on its
observed energetic output, LID-568 appeared to be consuming
infalling material - known as accretion - at more than 40 times
the hypothesized maximum, called the Eddington limit, for such
activity.
"The Eddington limit is a theoretical limit for the maximum
energy output the black hole can produce through the accretion
process. This theoretical limit assumes that the outward force
from the radiation produced during the accretion process
balances the gravity of the infalling material," said astronomer
and study co-author Julia Scharwächter of the Gemini Observatory
and NOIRLab.
These primordial black holes are thought to have originated
in one of two ways, either following the explosive death of the
universe's first generation of stars or through the collapse of
large clouds of gas present in the early universe.
"The discovery of LID-568 suggests that a significant
portion of mass growth can occur during a single episode of
rapid accretion. This could help explain how supermassive black
holes formed so early in the universe, regardless of how they
originated," Suh said.
"Until now, we have lacked observational confirmation of how
these black holes could grow so quickly in the early universe,"
Suh added.
A key sign of a growing supermassive black hole is emission
of X-rays, high-energy electromagnetic radiation with very short
wavelengths. Material swirling around a supermassive black hole
before it is consumed is superheated and glows strongly in X-ray
wavelengths. The researchers first spotted LID-568 using NASA's
Chandra X-ray Observatory and then studied it more closely using
Webb's infrared observational capabilities.
The Webb observations suggest the existence of some sort of
mechanism through which a black hole can gobble up material at a
faster pace than previously believed possible.
"LID-568 is remarkable due to its extreme growth rate and
the fact that it exists so early in the universe," Suh said. "We
don't know yet how LID-568 is able to exceed the Eddington
limit. To investigate further, we need more data, so we are
planning to conduct follow-up observations with Webb."
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