The James Webb Space Telescope has observed carbon-rich cosmic dust from the early universe. Probably its source is tiny grains of graphite and diamond. However, scientists are puzzled by one fact – according to classical models of the evolution of the Universe, so long ago these forms of carbon should not have even existed.
Billions of years had passed before the wealth of elements that today build the world around us appeared in the Universe. Initially, the universe contained only large amounts of hydrogen and helium – heavier molecules only appeared with stars and galaxies. As new observations from the James Webb Space Telescope, described in a study published in Nature, show, the first of them may have been born much earlier than we thought so far.
Coal from billions of years ago
An international team of scientists analyzed data from observations of cosmic dust – the matter that fills the space between celestial bodies. Although it makes it difficult to observe some stars by absorbing their light, scientists can use this property to determine the chemical composition of the dust. Researchers used it to look at clouds from the early universe, when it was less than a billion years old.
As it turned out, the dust grains were particularly strong at absorbing ultraviolet light with a wavelength of about 217.5 nanometers. The result was a surprise – so far such absorption has been observed only in the younger regions of the Universe, and its source was polycyclic aromatic hydrocarbons (PAHs), complex organic molecules. This finding, however, seemed implausible – many cycles of star formation and death would have to pass before such complex compounds could form. It would take much longer than a billion years.
Big, young dying stars
The researchers proposed a different hypothesis: instead of PAHs, Webb could have observed a different type of carbon-based molecule: tiny grains of graphite or diamond. They have a similar absorption spectrum to hydrocarbons, and most importantly, they may have formed much earlier than they did. “Nanodiamonds” can form in the material expelled from supernovae, and huge Wolf-Rayet stars that live fast and die young could eject fine carbon dust in less than a billion years.
The results turned out to be quite a surprise. They show us a whole new picture of the young universe – it may have been much more chemically active than we previously thought.
“I’ve been studying young galaxies my entire career and never expected to find such a clear signature of cosmic dust in such a long time ago,” said co-author Renske Smit of the University of Cambridge. “These data show us that carbon dust grains could have formed in the most primal systems. This disproves existing theories and opens up a completely new way for us to study the chemistry of the first galaxies, she added.
University of Cambridge, Science Alert
Main photo source: ESA/NASA/CSA/M. Zamani/PDRs4All ERS