Out there: How to create a black hole out of thin air
Natarajan and her colleagues propose that UHZ-1, and so perhaps many supermassive black holes, began as primordial clouds
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How many ways are there to leave this universe? Perhaps the best known exit entails the death of a star. In 1939, physicist J. Robert Oppenheimer and his student Harlan Snyder, of the University of California, Berkeley, predicted that when a sufficiently massive star runs out of thermonuclear fuel, it collapses inward and keeps collapsing forever, shrink-wrapping space, time and light around itself in what today is called a black hole. But it turns out that a dead star might not be needed to make a black hole. Instead, at least in the early universe, giant clouds of primordial gas may have collapsed directly into black holes, bypassing millions of years spent in stardom.
That is the tentative conclusion recently reached by a group of astronomers studying UHZ-1, a speck of light dating from not long after the Big Bang. In fact, UHZ-1 is (or was) a powerful quasar that spat fire and X-rays from a monstrous black hole 13.2 billion years ago, when the universe was not quite 500 million years young.
That is unusually soon, cosmically speaking, for so massive a black hole to have come into being through stellar collapses and mergers. Priyamvada Natarajan, an astronomer at Yale University and lead author of a paper published in the Astrophysical Journal Letters, and her colleagues contend that in UHZ-1 they have discovered a new celestial species, which they call an over-massive black hole galaxy, or OBG In essence, an OBG is a young galaxy anchored by a black hole that became too big too fast. The discovery of this precocious quasar could help astronomers solve a related puzzle that has tantalized them for decades. Nearly every galaxy visible in the modern universe seems to harbor at its center a supermassive black hole millions of billions of times as massive as the sun. Where did those monsters come from? Could ordinary black holes have grown so large so fast?
Natarajan and her colleagues propose that UHZ-1, and so perhaps many supermassive black holes, began as primordial clouds. These clouds could have collapsed into kernels that were precociously heavy — and were sufficient to jump-start the growth of over-massive black hole galaxies. They are another reminder that the universe we see is governed by the invisible geometry of darkness.
“As the first OBG candidate, UHZ-1 provides compelling evidence for the formation of heavy initial seeds from direct collapse in the early universe,” Natarajan and her colleagues wrote. In an email, she added: “Nature does seem to make BH seeds many ways, beyond just stellar death!”
Daniel Holz, a theorist at the University of Chicago who studies black holes, said: “Priya has found an extremely exciting black hole, if true.” He added, “It is simply too big too early. It’s like looking in at a kindergarten classroom and there among all the 5-year-olds is one that is 150 pounds and/or 6 feet tall.”
According to the story that astronomers have been telling themselves about the evolution of the universe, the first stars condensed out of clouds of hydrogen and helium left over from the Big Bang. They burned hot and fast, quickly exploding and collapsing into black holes 10 to 100 times as massive as the sun. Over eons, successive generations of stars were formed from the ashes of previous stars, enriching the chemistry of the cosmos. And the black holes left over from their deaths kept merging and growing somehow, into the supermassive black holes at the centers of galaxies.
