Every since scientists found supermassive black holes in the early universe, they have been trying to figure out what they ate.

Models of the early universe predicted that most of the gas and dust present would be used up by star formation. But new research suggests an excess of gas surrounding young galaxies would have helped sate growing black holes in the early universe.

"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," lead researcher Emanuele Paolo Farina, of the Max Planck Institute for Astronomy in Heidelberg, Germany, said in a news release.

Until now, scientists weren't sure how supermassive black holes grew to such great sizes so shortly after the Big Bang.

"The presence of these early monsters, with masses several billion times the mass of our sun, is a big mystery," said Farina.

Farina and his colleagues were able to spot the gas and dust that fueled the rapid growth of early supermassive black holes using the European Southern Observatory's Atacama Large Millimeter/submillimeter Array, or ALMA.

Using ALMA's MUSE instrument, researchers imaged several quasars, supermassive black holes at the centers of galaxies, in the distant universe. The quasars appeared as they were when the universe was just 870 million years old. The images, described this week in the Astrophysical Journal, revealed massive reservoirs of cool, dense hydrogen gas surrounding 12 of the 31 surveyed quasars.

The gas halos imaged by MUSE, the Multi Unit Spectroscopic Explorer, extended out some 100,000 light-years from the centers of each quasar. Scientists suggest the gas would have offered plenty of sustenance to the rapidly growing black holes.

In the future, scientists hope to image quasars and galaxies in the early universe in even more detail using the Extremely Large Telescope — currently under construction and expected to capture first light in 2025.

"With the power of the ELT, we will be able to delve even deeper into the early Universe to find many more such gas nebulae," Farina said.