The Oldest Black Hole Ever Found Is Almost as Old as the Universe Itself
The supermassive black hole formed during the earliest moments of the universe, which has researchers puzzled over how it got to be so big.
A huge black hole has just been discovered that is about 13 billion light-years old – almost as old as the universe itself. The find of this supermassive black hole is puzzling astronomers because they can't figure out how this black hole was formed so early in the universe's history.
The black hole, which is in the center of the quasar ULAS J1342+0928, is about 800 million times more massive than our sun. Scientists previously thought that black holes grow by picking up mass from the environment around them. But this black hole arose in a universe that was only 690 million years old — not nearly enough time to accumulate the mass needed to grow so big.
"It has an extremely high mass, and yet the universe is so young that this thing shouldn’t exist," Robert Simcoe, an astrophysicist at the Massachusetts Institute of Technology, said in a statement. "So there must be another way that it formed," he added. "And how exactly that happens, nobody knows."
Besides revealing a mystery about black hole formation, the new discovery sheds more light (so to speak) on when the first stars formed in the universe. Before first starlight, the universe was dominated by neutral hydrogen atoms.
As more stars and galaxies filled the void, their radiation began to energize the hydrogen, allowing the electrons bound to the nucleus to recombine and generate other chemical reactions. But when the black hole was formed, the universe was comprised of about 50 percent ionized (or energized) hydrogen and 50 percent neutral hydrogen.
"It’s a moment when the first galaxies emerged from their cocoons of neutral gas and started to shine their way out," Simcoe said. "This is the most accurate measurement of that time and a real indication of when the first stars turned on."
The black hole was found using an instrument called the Folded-port InfraRed Echellette (FIRE) that is installed on the 6.5-meter Magellan telescopes at Las Campanas Observatory in Chile. The discovery was made by Eduardo Bañados, an astrophysicist at the Carnegie Institution for Science and Princeton University.
Bañados was on a search for quasars, which are extremely bright objects that have a supermassive black hole embedded in them. What made this black hole stand out was its extremely high redshift, which refers to how the light from cosmic objects shifts to the redder end of the spectrum as the universe expands. The more distant the object, the more extreme the redshift. Also of interest was how fast gas moved inside of the quasar.
"Something is causing gas within the quasar to move around at very high speed, and the only phenomenon we know that achieves such speeds is orbit around a supermassive black hole," Simcoe said.
Observations from FIRE showed that much of the hydrogen around the quasar was neutral — not ionized. Extrapolating from FIRE's observations, the researchers determined the universe itself was about half neutral, half ionized when the quasar was formed. And that means that stars must have turned on at about the same time — just 690 million years after the Big Bang.
The research was supported by the National Science Foundation and published in the journal Nature.
"This adds to our understanding of our universe at large, because we’ve identified that moment of time when the universe is in the middle of this very rapid transition from neutral to ionized," Simcoe said. "We now have the most accurate measurements to date of when the first stars were turning on."
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