An international team of astronomers are studying 21 ancient quasi-stellar objects (or “quasars”) at the very limits of our observable universe. Each quasar has a supermassive black hole throbbing inside, sucking in the surrounding gas and growing to titanic masses exceeding 100 million suns.
“Quasars are a very early stage of galaxies, a sort of baby galaxies,” said Marianne Vestergaard, astrophysicist at the Dark Cosmology Center at the Niels Bohr Institute at the University of Copenhagen and co-author of a paper announcing these findings in the March 18 issue of Nature.
“Most galaxies have a massive black hole with a mass of over a million solar masses, but quasars are different. Their black holes are active and growing.”
The pair of distant quasars — named J0005-0006 and J0303-0019 — are approximately 13 billion light-years away (the light we receive from them is therefore 13 billion years old), meaning they formed less than 800 million years after the Big Bang. This fact makes these specimens pure; they are the “cleanest” quasars ever detected.
“We have found what are likely first-generation quasars, born in a dust-free medium and at the earliest stages of evolution,” said Linhua Jiang of the University of Arizona, Tucson and lead author of the study.
During the first few hundred million years after the Big Bang, there was no dust in the universe, just the most basic of gases. Before galaxies formed, it is thought primordial supermassive black holes were ignited as quasars, blasting the universe with intense X-ray radiation, so these earliest quasars wouldn’t have contained any dust.
However, this is the first time that observational evidence of dust-free quasars has been confirmed, providing a tantalizing glimpse at how these gargantuan black holes formed.
“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, leader of the original Sloan discovery team. “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.”
But where did these primordial black holes come from? It is theorized that these supermassive black holes are the leftovers from the dense energy conditions just after the Big Bang. But these recent findings suggest they gained mass very quickly during interstellar dust formation, causing them to grow and produce intense radiation as quasars.
They might even exist today as the supermassive black holes hiding in the centers of the galaxies. (Although there’s the highly speculative idea that “dark stars” may have spawned that particular breed of black hole.)
Image: An active primordial black hole surrounded by a glowing disk of gas (NASA/JPL-Caltech/R. Hurt).