An international team of astronomers has discovered 83 "quasars", extremely luminous active galactic nucleus powered by supermassive black holes in the distant universe, from a time when the universe was less than 10 per cent of its present age.
A supermassive black hole becomes visible when gas accretes onto it, causing it to shine as a quasar.
Using the massive Subaru Telescope, located at the Mauna Kea Observatory on Hawaii, the scientists from Japan, Taiwan and and the US, focussed their attention on objects located about 13 billion light years away from Earth.
They found 83 new very distant quasars. Together with 17 quasars, previously known in the survey region, the researchers found there was roughly one supermassive black hole per cubic giga light year.
The finding increases the number of black holes known at that epoch considerably and reveals, for the first time, how common they are in the universe's history.
"The quasars we discovered will be an interesting subject for follow-up observations with current and future facilities," said lead author Yoshiki Matsuoka, from the Ehime University in Japan.
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"We will also learn about formation and early evolution of supermassive black holes, by comparing the measured number density and luminosity distribution with predictions from theoretical models," Matsuoka said.
The study also provides new insight into the effect of black holes on the physical state of gas in the early universe in its first billion years.
Supermassive black holes, found at the centres of galaxies, can be millions or even billions times more massive than the sun, and were likely born in the first few hundred million years after the Big Bang that took place 13.8 billion years ago.
"It is remarkable that such massive dense objects were able to form so soon after the Big Bang," said co-author Michael Strauss, Professor at Princeton University.
"Understanding how black holes can form in the early universe, and just how common they are, is a challenge for our cosmological models," Strauss said.
The research appears in a series of five papers published in The Astrophysical Journal and the Publications of the Astronomical Observatory of Japan.
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