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Astronomers explain what fed hungry supermassive black holes at dawn of universe

This illustration depicts a gas halo surrounding a quasar in the early universe. The quasar, in orange, has two powerful jets and a supermassive black hole at its center surrounded by a dusty disc. The gas halo of glowing hydrogen gas is represented in blue. ESO/M. Kornmesser

When the universe was less than a billion years old, the first stars formed in a period called the Cosmic Dawn and light spread across space for the first time. But these early stars weren’t alone — they were swiftly joined by enormous supermassive black holes.

We know that the development of supermassive black holes is intertwined with the development of the galaxies which surround them, but astronomers have long wondered how supermassive black holes were able to form so close to the start of the universe, as they must have grown extremely fast. “The presence of these early monsters, with masses several billion times the mass of our sun, is a big mystery,” lead author Emanuele Paolo Farina of the Max Planck Institute for Astronomy in Heidelberg, Germany, said in a statement.

To grow so quickly, early supermassive black holes must have fed on huge amounts of dust and gas. However, before now astronomers had not observed large enough quantities of dust and gas to explain how these hungry monsters fed. Also, previous observations showed that much of the available dust and gas in the early universe were used up in the formation of stars.

Now, astronomers have been able to identify 12 examples of supermassive black hole buffets, where galaxies are surrounded by enormous halos of cool gas which could have fed early black holes.

To identify the gas halos, the team used the Very Large Telescope to survey quasars — very bright areas of gas which is falling into a supermassive black hole. Although we can’t observe the black holes directly, we can see bright regions called active galactic nuclei where gas gives off electromagnetic radiation as it is consumed by the black hole. By looking at 31 of these quasars which are very distant from Earth, the astronomers could essentially look back in time to see them as they were more than 12.5 billion years ago.

Of these quasars, 12 had hydrogen gas halos which spread as far as 100,000 light-years from the center of the galaxies and which had a mass of billions of times that of the sun.

“We are now able to demonstrate, for the first time, that primordial galaxies do have enough food in their environments to sustain both the growth of supermassive black holes and vigorous star formation,” Farina said in the same statement. “This adds a fundamental piece to the puzzle that astronomers are building to picture how cosmic structures formed more than 12 billion years ago.”

The research is published in The Astrophysical Journal.

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