Primordial Black Holes Formed Just After Big Bang
Illustration of a young black hole, such as the two distant dust-free quasars spotted recently by the Spitzer Space Telescope.
A pair of primordial black holes have been spotted so far away that they likely formed relatively soon after the Big Bang, scientists announced Wednesday.
The primitive form of the black holes suggests that they were created when the universe was much different than it is today.
The Big Bang is thought to have formed our universe about 13.7 billion years ago. The newly discovered black holes appear to be about 13 billion light-years away from Earth, meaning their light traveled 13 billion years to get to our telescopes. So scientists must be seeing them as they looked less than a billion years after the birth of the universe.
The black holes are extremely bright objects called quasars, where matter falling into a black hole flings out powerful jets of light into space. But these odd-ball quasars lack the hot dust that is usually seen in such objects.
That tells the researchers that they may have been created so early in the universe's history that dust did not yet exist.
"We think these early black holes are forming around the time when the dust was first forming in the universe, less than one billion years after the Big Bang," said Xiaohui Fan, an astronomer at the University of Arizona. "The primordial universe did not contain any molecules that could coagulate to form dust. The elements necessary for this process were produced and pumped into the universe later by stars."
Fan and his team detailed their discovery in the March 18 issue of the journal Nature.
The researchers discovered the two dust-free quasars, called J0005-0006 and J0303-0019, using NASA's Spitzer Space Telescope, which observes the universe in infrared light. Until now, no quasars have been spotted without dust anywhere in the universe.
"This is a remarkable ? and puzzling ? result, because hot-dust emission was thought to be a ubiquitous feature of quasars," wrote astronomer Giulia Stratta of the ASI Science Data Center in Italy in an accompanying essay in the same issue of Nature. Stratta was not involved in the research. "These apparently hot-dust-free quasars have no analogues [nearby]."
Another odd aspect of the two black holes is that they are the smallest in the sample of other distant quasars in which they were found. These two have masses of about 200 million to 300 million suns, while the rest of their peers generally weigh even more.
This clue also points to these quasars being extremely young and at an early stage of development, the researchers say.
"It appears we have found what are likely primitive first-generation quasars, that are born in a dust-free medium shortly after Big Bang," said co-researcher Marianne Vestergaard, an astrophysicist at the University of Copenhagen in Denmark. "It is fantastic that we are witness to this building up of black holes and the amount of heavier elements in the form of dust."
It is only because quasars are so bright that these young objects near the horizon of our universe are visible.
"Quasars emit an enormous amount of light, making them detectable literally at the edge of [the] observable universe," Fan said.
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