The mass of the most distant black hole yet known has been determined.
By Helen Briggs
BBC News Online science reporter
It weighs in at one quadrillion (1,000,000,000,000,000) times that of the Earth.
Heart of a quasar: a black hole is hidden in gas and dust
Put another way, it is the mass of three billion Suns.
This huge number is not unusual for a black hole but what is surprising is that such a massive structure formed so early in the history of the Universe.
It is 13 billion light-years away from Earth, so what we are seeing now gives a picture of the Universe when it was very youthful.
The huge black hole is at the centre of what is known as a quasar.
These extremely luminous objects are most probably galaxies that contain gigantic black holes.
The mass of the black hole at the heart of quasar (SDSS J1148+5251) was calculated by measuring a characteristic feature in its infrared light spectrum and comparing it with closer quasars.
The result confirms that huge black holes did exist in the Universe when it was only 6% of its current age.
What are quasars?
Bright and distant objects that were more common in the early Universe
A quasar emits a huge amount of energy - up to 10,000 times that of the whole Milky Way galaxy
They are just one type of the many active galaxies now visible to us
Matt Jarvis of Oxford University, UK, is one of the scientists behind the discovery.
He said the work helped astronomers trace "the evolution of the relationship between the black hole mass and the galaxy mass over the entire history of the Universe".
Ross McLure, from the Institute for Astronomy in Edinburgh, UK, added: "This quasar pinpoints the first massive structures to have formed in the Universe.
"It confirms predictions that such huge black holes do exist so early in the Universe, but they are rare."
Chris Done, a physicist at Durham University, UK, said black holes were typically a few billion times the mass of our Sun but it was a surprise to find one so massive so far away.
She told BBC News Online: "With it being so young, it hasn't had a lot of time, yet it has already collapsed into a black hole that is perfectly normal compared with what we see around us now."
Richard McMahon, of the Institute of Astronomy at the University of Cambridge, UK, described the finding as "very significant".
"This massive black hole existed 8,000 million years before the Earth formed but it was as massive as most black holes known in the Universe," he said.
The observations were made by the United Kingdom Infrared Telescope (UKIRT) in Hawaii by a team of astronomers from the UK and Canada.
The research, led by Chris Willott, is published in the electronic edition of Astrophysical Journal Letters.