Jacinta Bowler
Researchers from Denmark and Australia who have used the James Webb Space Telescope (JWST) to delve back to just 600 million years after the Big Bang say we might have to rethink our understanding of galaxy evolution.
Their conclusions come after they discovered that ancient galaxies from that time period are chemically very different from what was expected.
The findings were published in Nature Astronomy.
“It was like the galaxies had a rulebook that they followed – but astonishingly, this cosmic rulebook, appears to have undergone a dramatic rewrite during the universe’s infancy,” says radio astronomer Associate Professor Claudia Lagos, at The University of Western Australia.
“The most surprising discovery was that ancient galaxies produced far fewer heavy elements than we would have predicted based on what we know from galaxies that formed later.”
In astronomy terminology ‘heavy elements’ or ‘metals’ are any element that’s not hydrogen or helium.
“In fact, their chemical abundance was approximately four times lower than anticipated, based on the fundamental-metallicity relation observed in later galaxies,” Lagos adds.
The evolution of galaxies has changed throughout the ages, but these changes have been based on the chemical abundance, star formation rates and solar masses. This relationship scales, and so scientists can predict how old a galaxy should be.
However, these ancient galaxies from so close to the Big Bang are not following this pattern.
The researchers suggest that this could be because of the “intergalactic medium,” the hot gas that still exists between galaxies today.
They suggest 600 million years after the Big Bang, galaxies might still have been connected with the intergalactic medium, and this could allow them to receive extra gas which would dilute the amount of metals or heavy elements.
“The early galaxies continually received new, pristine gas from their surroundings, with the gas influx diluting the heavy elements inside the galaxies, making them less concentrated,” Lagos said.
As usual in science, the work isn’t done. While this discovery challenges what we know about galaxy evolution in the early Universe, more research will need to be done to confirm this theory.
