A research team from across the world has announced the discovery of the most distant black hole yet. It formed when the Universe was still in its infancy.
Eduardo Bañados, from the Carnegie Institution for Science, and his team combed a tenth of the night sky for quasars, which contain ancient and bright supermassive black holes from the furthest reaches of the Universe. Although they found only one quasar, dubbed ULAS J1342+0298, the results (published today in Nature) are striking: researchers see this quasar as it would have been 13 billion years ago, when the universe was 690 million years old.
For comparison, the oldest previously known quasar, ULAS J1120+0461, is eighty million years younger – the light we see from it dates back to 770 million years after the Big Bang.
J1342+0298 may be young, but it harbours a supermassive black hole 800 million times the mass of our Sun. “The new quasar is itself one of the first galaxies, and yet it already harbours a behemoth black hole as massive as others in the present-day Universe!” said co-author Xiaohui Fan from the University of Arizona.
Bañados and his team haven’t just broken a record – they’ve raised questions about the evolution of the Universe. The formation of supermassive black holes, which can weigh in at billions of solar masses, is still not completely understood; searching for the oldest among them can give researchers clues as to how they might have formed.
In the case of J1342+0298, explaining how a supermassive black hole which wouldn’t look out of place today could form raises issues with our models of how black holes evolve. “Gathering all this mass in fewer than 690 million years is an enormous challenge for theories of supermassive black hole growth,” said Bañados.
Equally, J1342+0298 might just have been lucky, says Fan. According to him, it may be “probably just an early bloomer. If it is located in a denser than average part of the universe, it could get an earlier start in life and grow more quickly.”
Quasars can also shed light on the early Universe. Around 380,000 years after the Big Bang, the Universe had cooled down enough for protons and electrons to become bound and form the first hydrogen atoms in an epoch (time period) known as recombination. Astronomers call this neutral hydrogen – the kind of hydrogen you might think of.
Several hundreds of millions of years after recombination, the ultraviolet radiation from the first stars, galaxies and accretion disks around black holes stripped the electrons from the hydrogen nuclei and reionised nearly all of the hydrogen in the Universe.
Researchers don’t know exactly when reionisation took place, but the discovery of J1342+0298 is helping to pin down times: the area surrounding the quasar primarily contained neutral hydrogen rather than hydrogen ions. This lends support to models where reionisation occurs comparatively late in the Universe’s history.
Finally, quasars play a role in our understanding of galaxy formation. When the team observed the quasar’s host galaxy, they found that it contained dust and heavier elements such as carbon and oxygen, indicating that many stars had already formed. 690 million years is a comparatively short time for so many stars to form, raising issues with our models.
J1342+0298 is a remarkable quasar and raises more questions than it answers. Fortunately, somewhere between 20 and 100 more quasars are predicted to exist; the team plans to continue searching for them over the whole sky.
These quasars will doubtless help astronomers to understand how the Universe evolved and, in Bañados’ words, “keep theorists very busy”. One might even harbour an even more distant black hole!
Related: Black hole is a record-breaker
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