Astronomers using the James Webb Space Telescope have discovered powerful winds blasting out of some of the universe’s earliest galaxies, offering new clues about how giant galaxies stopped forming stars surprisingly soon after the Big Bang.
The study, published in Nature, focused on quasars, some of the brightest and most energetic objects in the universe.
Quasars form when enormous black holes at the centers of galaxies pull in huge amounts of gas. As the gas spirals inward, it heats up and releases massive amounts of radiation.
These black holes are incredibly large, sometimes more than a billion times the mass of the sun.
What puzzles scientists is that such giant black holes already existed only a few hundred million years after the Big Bang, when the universe was still very young.
For years, scientists predicted that quasars should create extremely powerful “galactic winds” capable of pushing gas out of galaxies at tremendous speeds.
Because gas is the raw material needed to form stars, these winds could effectively shut down star formation.
Until now, however, direct evidence for such winds in the earliest quasars had remained uncertain.
The new research provides some of the clearest evidence yet that these winds were common in the young universe.
An international team led by researchers at the University of Arizona studied 27 distant quasars dating back to roughly one billion years after the Big Bang.
Among them, six quasars showed especially extreme outflows of gas moving at up to 8,400 kilometers per second, or about 5,000 miles per second. That is fast enough to travel from New York to Los Angeles in less than two seconds.
The team found that these violent outflows were much more common in the early universe than they are today. In fact, quasars with such extreme winds appeared at least four times more often in the distant universe than in later cosmic times.
Tiago Costa from Newcastle University, who previously developed theoretical models predicting these winds, said the findings strongly support long-standing ideas about how quasars influence galaxy evolution.
Scientists believe these winds may help explain another cosmic mystery. In recent years, astronomers have found many surprisingly massive galaxies that stopped forming stars much earlier than expected. Some of these galaxies already appeared “old” less than two billion years after the Big Bang.
The new results suggest quasars may be responsible.
As the black hole-powered winds sweep through a galaxy, they can remove enormous amounts of gas. Without gas, the galaxy loses the fuel needed to create new stars. Researchers estimate that some galaxies may have been losing gas equal to thousands of suns every year.
The study also suggests these powerful quasar phases do not last very long. The extreme outflows may remain active for only about 100 million years, which is brief on cosmic timescales.
After that, the galaxy becomes quiet, with little new star formation taking place.
The findings provide important new insight into how black holes may have shaped the growth of galaxies throughout cosmic history. Rather than simply sitting at the centers of galaxies, these giant black holes may have dramatically changed the fate of the galaxies around them, helping determine which galaxies continued forming stars and which became silent much earlier than expected.
Source: Newcastle University.
