Unexpected hydrogen signals challenge early universe theories
The James Webb Space Telescope has detected unexpected hydrogen radiation originating from a galaxy present in the early universe. This discovery is significant for understanding the early universe.
As specialists from the European Space Agency remind us, one of the key scientific goals of the James Webb Space Telescope is to study the origins of the universe more precisely than ever before. This pertains to the period when the first galaxies were forming.
The extraordinary high sensitivity of the telescope to infrared light is fundamental in this area. It opens up new possibilities for studying how these galaxies formed and what impact they had on the universe.
The telescope recently observed an extraordinarily distant galaxy, JADES-GS-z13-1, seen just 330 million years after the Big Bang. As a reminder, the universe is 13.8 billion years old.
Significantly stronger light emission
Scientists were very surprised by something. It involves the bright emission of light at a particular wavelength known as Lyman-alpha emission, which is produced by hydrogen atoms. The emission turned out to be much stronger than was thought possible at such an early stage of the universe's development.
"The early Universe was bathed in a thick fog of neutral hydrogen," shares Roberto Maiolino from the University of Cambridge and University College London.
"Most of this haze was lifted in a process called reionisation, which was completed about one billion years after the Big Bang," he explained "GS-z13-1 is seen when the Universe was only 330 million years old, yet it shows a surprisingly clear, telltale signature of Lyman-α emission that can only be seen once the surrounding fog has fully lifted. This result was totally unexpected by theories of early galaxy formation and has caught astronomers by surprise."
The discovery of Lyman-alpha radiation from this galaxy is significant for understanding the early universe, scientists emphasise.
The source of the detected radiation is not yet known. Researchers speculate that it could be the ionised hydrogen surrounding the galaxy, produced by a population of unusual, very massive, hot, and bright stars. These may have even been typical for that era. Another possibility could be an active galactic centre, powered by supermassive black holes.
Peter Jakobsen from the University of Copenhagen explained that while it was expected that Webb would surpass Hubble in detecting more distant galaxies, the true excitement lay in the unexpected insights it could offer—such as those about star formation and the appearance of black holes in the earliest periods of the universe.
