̽��ֱ�� of Cambridge - Canadian Space Agency

Cambridge academic named backup astronaut on Artemis II mission

sb726 — Wed, 06 Dec 2023 15:17:23 +0000

Dr Jenni Gibbons, Assistant Professor in Cambridge's Engineering department, is part of the Artemis II mission that will send humans around the moon and further into space than they have ever been.

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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Webb telescope reaches new milestone in its search for distant galaxies

sc604 — Fri, 09 Dec 2022 14:50:15 +0000

An international team of astronomers, including scientists at the Universities of Cambridge, Hertfordshire and Oxford, has reported the discovery of the earliest galaxies ever confirmed in our Universe.

Using data from the James Webb Space Telescope (JWST), scientists have confirmed observations of galaxies dating back to the earliest days of the Universe, less than 350 million years after the Big Bang – when the Universe was just 2% of its current age.

Images from JWST had previously suggested possible candidates for such early galaxies. Now, their age has been confirmed using long spectroscopic observations, which measure light to determine the speed and composition of objects in space.

These observations have revealed distinctive patterns in the tiny amount of light coming from these incredibly faint galaxies, allowing scientists to establish that the light they are emitting has taken 13.4 billion years to reach us, and corroborating their status as some of the earliest galaxies ever observed.

Scientists can also now confirm that two of these galaxies are further away than any observations made by the Hubble telescope – underlining JWST’s incredible power and ability to detect never-before-seen parts of the earliest Universe.

“It was crucial to prove that these galaxies do indeed inhabit the early Universe, as it’s very possible for closer galaxies to masquerade as very distant galaxies,” said Dr Emma Curtis-Lake from the ̽��ֱ�� of Hertfordshire, lead author on one of two papers on the findings. “Seeing the spectrum revealed as we hoped, confirming these galaxies as being at the true edge of our view, some further away than Hubble could see – it is a tremendously exciting achievement for the mission!”

̽��ֱ��findings have been achieved by an international collaboration of more than 80 astronomers from ten countries via the JWST Advanced Deep Extragalactic Survey (JADES) programme. ̽��ֱ��team were allocated just over a month of observation on the telescope, using the two on-board instruments: the Near-Infrared Spectrograph (NIRSpec) and the Near-Infrared Camera (NIRCam). These instruments were developed with the primary purpose of investigating the earliest and faintest galaxies.

“It is hard to understand galaxies without understanding the initial periods of their development,” said Dr Sandro Tacchella from Cambridge’s Cavendish Laboratory and Kavli Institute for Cosmology, co-lead author on the second paper. “Much as with humans, so much of what happens later depends on the impact of these early generations of stars. So many questions about galaxies have been waiting for the transformative opportunity of Webb, and we’re thrilled to be able to play a part in revealing this story.”

“For the first time, we have discovered galaxies only 350 million years after the big bang, and we can be absolutely confident of their fantastic distances,” said Brant Robertson from the ̽��ֱ�� of California Santa Cruz, co-lead author on the second paper. “To find these early galaxies in such stunningly beautiful images is a special experience.”

Across 10 days of their observation time, the JADES team of astronomers focused on a small patch of sky in and around Hubble Space Telescope’s Ultra Deep Field, which for over 20 years has been a favourite of astronomers and has been analysed at the limit of nearly every large telescope to have existed. However, with JWST, the team were able to observe in nine different infrared wavelength ranges, providing an exquisitely sharp and sensitive picture of the field. ̽��ֱ��image reveals nearly 100,000 galaxies, each billions of light years away, in a pinprick of the sky equivalent to looking at a mobile phone screen across a football field.

̽��ֱ��very earliest galaxies were identifiable by their distinctive banded colours, visible in infrared light but invisible in other wavelengths. In one rare continuous 28-hour observation window, the Near-Infrared Spectrograph was used to spread out the light emitting from each galaxy into a rainbow spectrum. This allowed astronomers to measure the amount of light received at each wavelength and study the unique light patterns created by the properties of the gas and stars within each galaxy.

Crucially, four of the galaxies were revealed to originate earlier in the Universe than any previous observations.

“Our observations suggest that the formation of the first stars and galaxies started very early in the history of the Universe,” said Professor Andrew Bunker from the ̽��ֱ�� of Oxford.

“This is a major leap forward in our understanding of how the first galaxies formed,” said Professor Roberto Maiolino from Cambridge’s Cavendish Laboratory and Kavli Institute for Cosmology, co-author on one of the two papers. “We have been able to dissect the light coming from these galaxies in the very early universe and, for the first time, characterise in detail their properties. It’s really fascinating and intriguing to discover how young these systems were and that stellar processes hadn’t yet managed to pollute these galaxies with chemical elements heavier than helium.”

Astronomers in the JADES team now plan to focus on another area of the sky to conduct further spectroscopy and imaging, hoping to reveal more about the earliest origins of our Universe and how these first galaxies evolve with cosmic time.

More information about the findings can be found in a newly-published NASA blog. Pre-prints of the team’s two papers, which have not yet been peer-reviewed, are available online.

̽��ֱ��James Webb Space Telescope is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency). Sandro Tacchella is a Fellow of St Edmund’s College, Cambridge.

Adapted from a ̽��ֱ�� of Hertfordshire media release.

New findings confirm that JWST has surpassed the Hubble telescope in its ability to observe the early Universe

So many questions about galaxies have been waiting for the transformative opportunity of Webb, and we’re thrilled to be able to play a part in revealing this story

Sandro Tacchella

NASA, ESA, CSA, M. Zamani (ESA/Webb)

This image taken by the James Webb Space Telescope highlights the region of study by the JWST Advanced Deep Extragalactic Survey (JADES).

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 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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