The Largest Black Holes in the Universe Formed in a Snap — Then Stopped

An artist's illustration depicts a quasar, or supermassive, ultra-luminous black hole.

About 13 billion years ago, when our universe was still just a scrappy startup, the cosmos hit a creative streak and churned out supermassive black holes left, right and center.

Astronomers can still sneak a peek at these relics of the early universe when they look at quasars, incredibly large, outstandingly bright objects thought to be powered by old black holes billions of times more massive than Earth's sun. However, the very existence of these ancient objects poses a problem. Many quasars appear to originate from the first 800 million years of the universe, long before any stars could grow big or old enough to collapse under their own mass, explode in a supernova and form a black hole.

So, where are these old holes in the fabric of space-time coming from? According to one popular theory, maybe all it takes is a whole lot of gas.

In a new study, published June 28 in The Astrophysical Journal Letters, researchers ran a computer model to show that certain supermassive black holes in the very early universe could have formed by simply accumulating a gargantuan amount of gas into one gravitationally bound cloud. The researchers found that, in a few hundred million years, a sufficiently large such cloud could collapse under its own mass and create a small black hole — no supernova required.

These theoretical objects are known as direct collapse black holes (DCBHs). According to black hole expert Shantanu Basu, lead author of the new study and an astrophysicist at Western University in London, Ontario, one of the defining features of DCBHs is that they must have formed very, very quickly within a very brief time period in the early universe.

"The black holes are formed over a duration of only about 150 million years and grow rapidly during this time," Basu told Live Science in an email. "The ones that form in the early part of the 150-million-year time window can increase their mass by a factor of 10 thousand."

How does a cloud of gas become a black hole? According to a 2017 study, such a transformation requires two galaxies with very different personalities: one of them a cosmic overachiever that's forming lots of baby stars and the other a low-key heap of starless gas.

As new stars form in the busy galaxy, they blast out a constant stream of hot radiation that washes over the neighboring galaxy, preventing the gas there from coalescing into stars of its own. Within a few hundred million years, that starless gas cloud could accrete so much matter that it simply collapses under its own weight, forming a black hole without ever producing a star, Basu found.

Soon, this "seed" black hole could go on to reach supermassive status by rapidly gobbling up matter from nearby nebulae — possibly giving birth to the gargantuan quasars we can see today.