̽��ֱ�� of Cambridge - Joris Witstok

Webb Telescope sees galaxy in mysteriously clearing fog of early Universe

sc604 — Wed, 26 Mar 2025 16:00:00 +0000

A key goal of the NASA/ESA/CSA James Webb Space Telescope has been to see further than ever before into the distant past of our Universe, when the first galaxies were forming after the Big Bang, a period know as cosmic dawn.

Researchers studying one of those very early galaxies have now made a discovery in the spectrum of its light, that challenges our established understanding of the Universe’s early history. Their results are reported in the journal Nature.

Webb discovered the incredibly distant galaxy JADES-GS-z13-1, observed at just 330 million years after the Big Bang. Researchers used the galaxy’s brightness in different infrared filters to estimate its redshift, which measures a galaxy’s distance from Earth based on how its light has been stretched out during its journey through expanding space.

̽��ֱ��NIRCam imaging yielded an initial redshift estimate of 12.9. To confirm its extreme redshift, an international team led by Dr Joris Witstok, previously of the ̽��ֱ�� of Cambridge’s Kavli Institute for Cosmology, observed the galaxy using Webb’s Near-Infrared Spectrograph (NIRSpec) instrument.

̽��ֱ��resulting spectrum confirmed the redshift to be 13.0. This equates to a galaxy seen just 330 million years after the Big Bang, a small fraction of the Universe’s present age of 13.8 billion years.

But an unexpected feature also stood out: one specific, distinctly bright wavelength of light, identified as the Lyman-α emission radiated by hydrogen atoms. This emission was far stronger than astronomers thought possible at this early stage in the Universe’s development.

“ ̽��ֱ��early Universe was bathed in a thick fog of neutral hydrogen,” said co-author Professor Roberto Maiolino from Cambridge’s Kavli Institute for Cosmology. “Most of this haze was lifted in a process called reionisation, which was completed about one billion years after the Big Bang.

“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.”

Before and during the epoch of reionisation, neutral hydrogen fog surrounding galaxies blocked any energetic ultraviolet light they emitted, much like the filtering effect of coloured glass. Until enough stars had formed and were able to ionise the hydrogen gas, no such light — including Lyman-α emission — could escape from these fledgling galaxies to reach Earth.

̽��ֱ��confirmation of Lyman-α radiation from this galaxy has great implications for our understanding of the early Universe. “We really shouldn’t have found a galaxy like this, given our understanding of the way the Universe has evolved,” said co-author Kevin Hainline from the ̽��ֱ�� of Arizona. “We could think of the early Universe as shrouded with a thick fog that would make it exceedingly difficult to find even powerful lighthouses peeking through, yet here we see the beam of light from this galaxy piercing the veil.”

̽��ֱ��source of the Lyman-α radiation from this galaxy is not yet known, but it may include the first light from the earliest generation of stars to form in the Universe. “ ̽��ֱ��large bubble of ionised hydrogen surrounding this galaxy might have been created by a peculiar population of stars — much more massive, hotter and more luminous than stars formed at later epochs, and possibly representative of the first generation of stars,” said Witstok, who is now based at the Cosmic Dawn Center at the ̽��ֱ�� of Copenhagen. A powerful active galactic nucleus, driven by one of the first supermassive black holes, is another possibility identified by the team.

̽��ֱ��team plans further follow-up observations of GS-z13-1, aiming to obtain more information about the nature of this galaxy and origin of its strong Lyman-α radiation. Whatever the galaxy is concealing, it is certain to illuminate a new frontier in cosmology.

JWST is an international partnership between NASA, ESA and the Canadian Space Agency (CSA). ̽��ֱ��data for this result were captured as part of the JWST Advanced Deep Extragalactic Survey (JADES).

Reference:
Joris Witstok et al. ‘Witnessing the onset of reionization through Lyman-α emission at redshift 13.’ Nature (2025). DOI: 10.1038/s41586-025-08779-5

Adapted from an ESA media release.

Astronomers have identified a bright hydrogen emission from a galaxy in the very early Universe. ̽��ֱ��surprise finding is challenging researchers to explain how this light could have pierced the thick fog of neutral hydrogen that filled space at that time.

This result was totally unexpected by theories of early galaxy formation and has caught astronomers by surprise

Roberto Maiolino

ESA/Webb, NASA, STScI, CSA, JADES Collaboration

JADES-GS-z13-1 in the GOODS-S field

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Webb sees carbon-rich dust grains in the first billion years of cosmic time

sc604 — Wed, 19 Jul 2023 15:00:48 +0000

Similar observational signatures have been observed in the much more recent universe, and have been attributed to complex, carbon-based molecules known as polycyclic aromatic hydrocarbons (PAHs). It is not thought likely, however, that PAHs would have developed within the first billion years of cosmic time.

̽��ֱ��international team, including researchers from the ̽��ֱ�� of Cambridge, say that Webb may have observed a different species of carbon-based molecule: possibly minuscule graphite- or diamond-like grains produced by the earliest stars or supernovas. Their results, which suggest that infant galaxies in the early universe developed much faster than anticipated, are reported in the journal Nature.

̽��ֱ��seemingly empty spaces in our universe are in reality often not empty at all, but are filled by clouds of gas and cosmic dust. This dust consists of grains of various sizes and compositions that are formed and ejected into space in a variety of ways, including by supernova events.

This material is crucial to the evolution of the universe, as dust clouds ultimately form the birthplaces for new stars and planets. However, the dust absorbs stellar light at certain wavelengths, making some regions of space challenging to observe.

An upside is that certain molecules will consistently absorb or otherwise interact with specific wavelengths of light. This means that astronomers can get information about the cosmic dust’s composition by observing the wavelengths of light that it blocks.

̽��ֱ��Cambridge-led team of astronomers used this technique, combined with Webb’s extraordinary sensitivity, to detect the presence of carbon-rich dust grains only a billion years after the birth of the universe.

“Carbon-rich dust grains can be particularly efficient at absorbing ultraviolet light with a wavelength around 217.5 nanometres, which for the first time we have directly observed in the spectra of very early galaxies,” said lead author Dr Joris Witstok from Cambridge’s Kavli Institute for Cosmology.

This 217.5-nanometre feature has previously been observed in the much more recent and local Universe, including within our own Milky Way galaxy, and has been attributed to two different types of carbon-based molecules: polycyclic aromatic hydrocarbons (PAHs) or nano-sized graphitic grains.

According to most models, it should take several hundreds of millions of years before PAHs form, so it would be surprising if the team had observed the chemical signature of molecules that shouldn’t have formed yet. However, according to the researchers, this result is the earliest and most distant direct signature for this carbon-rich dust grain.

̽��ֱ��answer may lie in the details of what was observed. ̽��ֱ��feature observed by the team peaked at 226.3 nanometres, not the 217.5-nanometre wavelength associated with PAHs and tiny graphitic grains. A discrepancy of less than ten nanometres could be accounted for by measurement error. Equally, it could also indicate a difference in the composition of the early universe cosmic dust mixture that the team detected.

“This slight shift in wavelength of where the absorption is strongest suggests we may be seeing a different mix of grains, for example, graphite- or diamond-like grains,” said Witstok, who is also a Postdoctoral Research Associate at Sidney Sussex College. “This could also potentially be produced on short timescales by Wolf-Rayet stars or by material ejected from a supernova.”

Models have previously suggested that nano-diamonds could be formed in the material ejected from supernovas; and huge, hot Wolf-Rayet stars, which live fast and die young, would give enough time for generations of stars to have been born, lived, and died, to distribute carbon-rich grains into the surrounding cosmic dust in under a billion years.

However, it is still a challenge to fully explain these results with the existing understanding of the early formation of cosmic dust. These results will go on to inform the development of improved models and future observations.

With the advent of Webb, astronomers are now able to make detailed observations of the light from individual dwarf galaxies, seen in the first billion years of cosmic time. Webb finally permits the study of the origin of cosmic dust and its role in the crucial first stages of galaxy evolution.

“This discovery was made possible by the unparalleled sensitivity improvement in near-infrared spectroscopy provided by Webb, and specifically its Near-Infrared Spectrograph (NIRSpec),” said co-author Professor Roberto Maiolino, who is based in the Cavendish Laboratory and the Kavli Institute for Cosmology. “ ̽��ֱ��increase in sensitivity provided by Webb is equivalent, in the visible, to instantaneously upgrading Galileo’s 37-millimetre telescope to the 8-metre Very Large Telescope, one of the most powerful modern optical telescopes.”

̽��ֱ��team is planning further research into the data and this result. “We are planning to work with theorists who model dust production and growth in galaxies,” said co-author Irene Shivaei of the ̽��ֱ�� of Arizona/Centro de Astrobiología (CAB). “This will shed light on the origin of dust and heavy elements in the early universe.”

These observations were made as part of the JWST Advanced Deep Extragalactic Survey, or JADES. This programme has facilitated the discovery of hundreds of galaxies that existed when the universe was less than 600 million years old, including some of the farthest galaxies known to date.

“I’ve studied galaxies in the first billion years of cosmic time my entire career and never did we expect to find such a clear signature of cosmic dust in such distant galaxies,” said co-author Dr Renske Smit from Liverpool John Moores ̽��ֱ��. “ ̽��ֱ��ultradeep data from JWST is showing us that grains made up of diamond-like dust can form in the most primordial of systems. This is completely overthrowing models of dust formation and opening up a whole new way of studying the chemical enrichment of the very first galaxies.”

Webb is an international partnership between NASA, ESA and the Canadian Space Agency (CSA). This research was supported in part by the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

Reference:
Joris Witstok et al. ‘Carbonaceous dust grains seen in the first billion years of cosmic time.’ Nature (2023). DOI: 10.1038/s41586-023-06413-w

Adapted from an ESA press release.

For the first time, the James Webb Space Telescope has observed the chemical signature of carbon-rich dust grains in the early universe.

ESA/Webb, NASA, ESA, CSA

Galaxy JADES-GS-z6 in the GOODS-S field: JADES (NIRCam image)

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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