After the Big Bang, black holes grew supermassive by feeding on gas and dust stashes, finds study

Until now, scientists did not understand how supermassive black holes grew so large, so early in the universe. Neither did they spot 'black hole food'  in large enough quantities to explain this rapid growth, until now, says a new study. 


                            After the Big Bang, black holes grew supermassive by feeding on gas and dust stashes, finds study
Supermassive black holes are known for their voracious appetite, constantly feeding on dust and gas in their vicinity (Getty Images)

The supermassive black holes -- which are millions or billions of times as massive as the Sun -- are known for their voracious appetite, constantly feeding on dust and gas in their vicinity. Even in their formative years, these monsters were just as massive, but scientists did not understand how they grew so big, so early in the universe. Neither did they spot 'black hole food' in large enough quantities to explain this rapid growth, until now.

A new study suggests that supermassive black holes had enough 'stashes of food' -- that is, gas and dust -- around them to support their growth. "We are now able to demonstrate, for the first time, that early galaxies did have enough food in their environs to support the growth of supermassive black holes and stars. This adds a fundamental piece to the puzzle that astronomers are building to picture how cosmic structures formed more than 12 billion years ago," Emanuele Paolo Farina, of the Max Planck Institute for Astronomy in Heidelberg, Germany, who led the research published today in The Astrophysical Journal.

The first few black holes may have been created after the collapse of the first stars. "A typical black hole forms just after the Big Bang with a mass of "only'' a few hundred times the one of the sun. To become one of the massive and evolved objects [supermassive black holes], it must have constantly devoured an enormous amount of gas (the black hole food) during its entire life," Farina told MEA WorldWide (MEAWW).

To analyze the surroundings of the most massive and voracious black holes present in the young universe, Farina and his colleagues turned ESO's Very Large Telescope (VLT) powerful eyes towards quasars -- extremely bright celestial objects that surround supermassive black holes. They were hoping to look for gas reservoirs around quasars, which are difficult to observe. "Direct observations of the gas located in the close environs of massive galaxies is a necessary piece of information for our understanding of their formation and evolution", says Farina.

The team could detect the faint glow of the hydrogen gas in the halos, allowing astronomers to finally reveal the food stashes that power supermassive black holes in the early Universe. (ESO/Farina et al.; ALMA (ESO/NAOJ/NRAO), Decarli et al)

A sophisticated instrument called MUSE, which is a part of VLT, peered through 31 quasars. They saw enormous gas reservoirs: halos of cool, dense hydrogen gas -- seen as they were over 12.5 billion years ago. The gas halos extended 100,000 light years from the central black holes and with billions of times the mass of the Sun, says the study.

Of these, they found gas halos --  located within a hundred thousands of light years from the central black hole -- stored around 12 quasars. "The observations also revealed that these storages are tightly bound to the galaxies hosting the black holes. Thus they are available to satisfy the greedy forage for gas of these objects." Farina told MEAWW. 

In the future, ESO's Extremely Large Telescope will help scientists to look back in time, to the first couple of billion years after the Big Bang, to understand the early history of galaxies and supermassive black holes. "With the power of the Extremely Large Telescope (ELT), we will be able to delve even deeper into the early Universe to find many more such gas nebulae," Farina says. The ELT, which is under construction, is set to become "the world's biggest eye on the sky". 

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