Superbright Blazars Reveal Monster Black Holes Roamed the Early Universe
The discovery of so many supermassive black holes existing when the universe was only 1.4 billion years old adds to the mystery of how the biggest black holes evolved.
The early universe may be filled with black holes a billion times bigger than the sun, though how they managed to grow so large so quickly remains a mystery.
Astronomers using NASA's Fermi gamma ray observatory found five bright objects known as blazars whose light has been traveling through space for some 13 billion years, making them the most distant blazars found yet.
Blazars occur when the jet of a supermassive black hole is pointing toward Earth. They are among the most energetic objects in the universe and prized by black hole hunters, who have to resort to surreptitious means to find their prey.
Black holes are objects so dense with matter than not even light can escape their gravitational fists. But as a black hole feeds, material swirling toward the event horizon (the point of no escape) spews telltale radiation, revealing its approximate size and location.
Some black holes also create jets of gas that shoot off from opposite sides of their cores. When a jet faces Earth, that's a blazar.
Finding five blazars when the universe was just 1.4 billion years old - one-tenth its current age - adds to an ongoing debate about the relationship between galaxies and black holes and how they evolved over time.
Previously, the most distant blazars date back to when the universe was about 2.1 billion years old.
The discovery of five blazars from the universe's youth means there must be hundreds more similar objects, said astronomer Roopesh Ojha, with NASA's Goddard Space Flight Center in Greenbelt, Md.
"For the one object you see, there's something closer to 600 that you don't see," Ojha told reporters during a webcast press conference at the American Physical Society meeting in Washington DC this week.
Two of the five blazars are so big that their respective black holes may be more than a billion times the mass of the sun, Ojha added.
(The black hole at the center of our Milky Way galaxy, by comparison, is about 4 millions times the mass of the sun.)
"There's a challenge in how do you explain the presence of supermassive black holes... so early in the universe? We've probably just made this problem a little bit more difficult," Ojha said.
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