Scientists discover how the universe's first quasar formed

The mystery of how the universe’s first quasars formed – something that has puzzled scientists for nearly 20 years – has now been solved by a team of astrophysicists whose findings were published in Nature today.

The existence of more than 200 quasars powered by supermassive black holes less than a billion years after the Big Bang remains one of the outstanding problems in astrophysics because it is never fully understood how they formed so early.

A team of experts led by Dr Daniel Whalen from the University of Portsmouth has discovered that the first quasars formed naturally in the turbulent conditions of a rare gas reservoir in the early universe.

The first supermassive black holes were simply a natural consequence of the formation of structures in the cosmology of cold dark matter – children of the cosmic web.

Dr Whalen, from the University’s Institute of Cosmology and Gravity, said: “This discovery is very exciting because it has reversed 20 years of thinking about the origin of the universe’s first supermassive black hole.

“We found a supermassive black hole at the center of today’s most massive galaxy, which could be millions or billions of times the mass of the sun. But in 2003 we started discovering quasars – supermassive black holes that are extremely luminous and actively accreting like cosmic lighthouses in the early universe – which existed less than a billion years after the Big Bang. And no one understands how they formed in such early times.”

Several years ago, supercomputer simulations showed that early quasars could have formed at the junction of rare, cold, and powerful gas streams. Only a dozen of these exist in a volume of space a billion light years away, but a black hole must be 100,000 solar masses at birth. Today’s black holes form when massive stars run out of fuel and collapse, but are usually only 10 – 100 solar masses.

Astrophysicists have long theorized that 10,000 – 100,000 solar-mass stars formed in the early universe but only in finely tuned exotic environments such as a strong ultraviolet background or supersonic flow between gas and dark matter that bear no resemblance to turbulent clouds where the first quasars to form.

Supercomputer simulation of primordial quasar birth

Dr Whalen said: “We think these stars are a bit like dinosaurs on earth, they are very large and primitive. And they have short lives, only living for a quarter of a million years before collapsing into a black hole.

“Our supercomputing model goes back very early and finds that dense, cold gas streams capable of growing a billion sun-mass black holes in just a few hundred million years create their own supermassive stars without requiring an unusual environment. The cold stream pushed up the turbulence in the cloud that prevented normal stars from forming until the cloud became so massive that it collapsed simultaneously under its own weight, forming two gigantic primordial stars – one 30,000 times the mass of the sun and the other 40,000 in mass.

“As a result, the only primordial clouds that can form quasars right after cosmic dawn – when the universe’s first stars formed – also easily create their own massive seeds. This simple and beautiful result explains not only the origin of the first quasars but also their demographics – their early numbers.

“The first supermassive black holes were simply a natural consequence of the formation of structures in cold dark matter cosmology — children of the cosmic web.”

The paper The Turbulent Origins of the First Quasar is published in Nature.

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