̽��ֱ�� of Cambridge - UK Science and Technology Facilities Council

Massive black hole in the early universe spotted taking a ‘nap’ after overeating

sc604 — Wed, 18 Dec 2024 16:00:00 +0000

Like a bear gorging itself on salmon before hibernating for the winter, or a much-needed nap after Christmas dinner, this black hole has overeaten to the point that it is lying dormant in its host galaxy.

An international team of astronomers, led by the ̽��ֱ�� of Cambridge, used the NASA/ESA/CSA James Webb Space Telescope to detect this black hole in the early universe, just 800 million years after the Big Bang.

̽��ֱ��black hole is huge – 400 million times the mass of our Sun – making it one of the most massive black holes discovered by Webb at this point in the universe’s development. ̽��ֱ��black hole is so enormous that it makes up roughly 40% of the total mass of its host galaxy: in comparison, most black holes in the local universe are roughly 0.1% of their host galaxy mass.

However, despite its gigantic size, this black hole is eating, or accreting, the gas it needs to grow at a very low rate – about 100 times below its theoretical maximum limit – making it essentially dormant.

Such an over-massive black hole so early in the universe, but one that isn’t growing, challenges existing models of how black holes develop. However, the researchers say that the most likely scenario is that black holes go through short periods of ultra-fast growth, followed by long periods of dormancy. Their results are reported in the journal Nature.

When black holes are ‘napping’, they are far less luminous, making them more difficult to spot, even with highly sensitive telescopes such as Webb. Black holes cannot be directly observed, but instead they are detected by the tell-tale glow of a swirling accretion disc, which forms near the black hole’s edges. When black holes are actively growing, the gas in the accretion disc becomes extremely hot and starts to glow and radiate energy in the ultraviolet range.

“Even though this black hole is dormant, its enormous size made it possible for us to detect,” said lead author Ignas Juodžbalis from Cambridge’s Kavli Institute for Cosmology. “Its dormant state allowed us to learn about the mass of the host galaxy as well. ̽��ֱ��early universe managed to produce some absolute monsters, even in relatively tiny galaxies.”

According to standard models, black holes form from the collapsed remnants of dead stars and accrete matter up to a predicted limit, known as the Eddington limit, where the pressure of radiation on matter overcomes the gravitational pull of the black hole. However, the sheer size of this black hole suggests that standard models may not adequately explain how these monsters form and grow.

“It’s possible that black holes are ‘born big’, which could explain why Webb has spotted huge black holes in the early universe,” said co-author Professor Roberto Maiolino, from the Kavli Institute and Cambridge’s Cavendish Laboratory. “But another possibility is they go through periods of hyperactivity, followed by long periods of dormancy.”

Working with colleagues from Italy, the Cambridge researchers conducted a range of computer simulations to model how this dormant black hole could have grown to such a massive size so early in the universe. They found that the most likely scenario is that black holes can exceed the Eddington limit for short periods, during which they grow very rapidly, followed by long periods of inactivity: the researchers say that black holes such as this one likely eat for five to ten million years, and sleep for about 100 million years.

“It sounds counterintuitive to explain a dormant black hole with periods of hyperactivity, but these short bursts allow it to grow quickly while spending most of its time napping,” said Maiolino.

Because the periods of dormancy are much longer than the periods of ultra-fast growth, it is in these periods that astronomers are most likely to detect black holes. “This was the first result I had as part of my PhD, and it took me a little while to appreciate just how remarkable it was,” said Juodžbalis. “It wasn’t until I started speaking with my colleagues on the theoretical side of astronomy that I was able to see the true significance of this black hole.”

Due to their low luminosities, dormant black holes are more challenging for astronomers to detect, but the researchers say this black hole is almost certainly the tip of a much larger iceberg, if black holes in the early universe spend most of their time in a dormant state.

“It’s likely that the vast majority of black holes out there are in this dormant state – I’m surprised we found this one, but I’m excited to think that there are so many more we could find,” said Maiolino.

̽��ֱ��observations were obtained as part of the JWST Advanced Deep Extragalactic Survey (JADES). ̽��ֱ��research was supported in part by the European Research Council and the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

Reference:
Ignas Juodžbalis et al. ‘A dormant overmassive black hole in the early Universe.’ Nature (2024). DOI: 10.1038/s41586-024-08210-5

Scientists have spotted a massive black hole in the early universe that is ‘napping’ after stuffing itself with too much food.

Jiarong Gu

Artist’s impression of a black hole during one of its short periods of rapid growth

̽��ֱ��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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Researchers deal a blow to theory that Venus once had liquid water on its surface

sc604 — Mon, 02 Dec 2024 16:01:07 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, studied the chemical composition of the Venusian atmosphere and inferred that its interior is too dry today for there ever to have been enough water for oceans to exist at its surface. Instead, the planet has likely been a scorching, inhospitable world for its entire history.

̽��ֱ��results, reported in the journal Nature Astronomy, have implications for understanding Earth’s uniqueness, and for the search for life on planets outside our Solar System. While many exoplanets are Venus-like, the study suggests that astronomers should narrow their focus to exoplanets which are more like Earth.

From a distance, Venus and Earth look like siblings: it is almost identical in size and is a rocky planet like Earth. But up close, Venus is more like an evil twin: it is covered with thick clouds of sulfuric acid, and its surface has a mean temperature close to 500°C.

Despite these extreme conditions, for decades, astronomers have been investigating whether Venus once had liquid oceans capable of supporting life, or whether some mysterious form of ‘aerial’ life exists in its thick clouds now.

“We won’t know for sure whether Venus can or did support life until we send probes at the end of this decade,” said first author Tereza Constantinou, a PhD student at Cambridge’s Institute of Astronomy. “But given it likely never had oceans, it is hard to imagine Venus ever having supported Earth-like life, which requires liquid water.”

When searching for life elsewhere in our galaxy, astronomers focus on planets orbiting their host stars in the habitable zone, where temperatures are such that liquid water can exist on the planet’s surface. Venus provides a powerful limit on where this habitable zone lies around a star.

“Even though it’s the closest planet to us, Venus is important for exoplanet science, because it gives us a unique opportunity to explore a planet that evolved very differently to ours, right at the edge of the habitable zone,” said Constantinou.

There are two primary theories on how conditions on Venus may have evolved since its formation 4.6 billion years ago. ̽��ֱ��first is that conditions on the surface of Venus were once temperate enough to support liquid water, but a runaway greenhouse effect caused by widespread volcanic activity caused the planet to get hotter and hotter. ̽��ֱ��second theory is that Venus was born hot, and liquid water has never been able to condense at the surface.

“Both of those theories are based on climate models, but we wanted to take a different approach based on observations of Venus’ current atmospheric chemistry,” said Constantinou. “To keep the Venusian atmosphere stable, then any chemicals being removed from the atmosphere should also be getting restored to it, since the planet’s interior and exterior are in constant chemical communication with one another.”

̽��ֱ��researchers calculated the present destruction rate of water, carbon dioxide and carbonyl sulphide molecules in Venus’ atmosphere, which must be restored by volcanic gases to keep the atmosphere stable.

Volcanism, through its supply of gases to the atmosphere, provides a window into the interior of rocky planets like Venus. As magma rises from the mantle to the surface, it releases gases from the deeper portions of the planet.

On Earth, volcanic eruptions are mostly steam, due to our planet’s water-rich interior. But, based on the composition of the volcanic gases necessary to sustain the Venusian atmosphere, the researchers found that volcanic gases on Venus are at most six percent water. These dry eruptions suggest that Venus’s interior, the source of the magma that releases volcanic gases, is also dehydrated.

At the end of this decade, NASA’s DAVINCI mission will be able to test and confirm whether Venus has always been a dry, inhospitable planet, with a series of flybys and a probe sent to the surface. ̽��ֱ��results could help astronomers narrow their focus when searching for planets that can support life in orbit around other stars in the galaxy.

“If Venus was habitable in the past, it would mean other planets we have already found might also be habitable,” said Constantinou. “Instruments like the James Webb Space Telescope are best at studying the atmospheres of planets close to their host star, like Venus. But if Venus was never habitable, then it makes Venus-like planets elsewhere less likely candidates for habitable conditions or life.

“We would have loved to find that Venus was once a planet much closer to our own, so it’s kind of sad in a way to find out that it wasn’t, but ultimately it’s more useful to focus the search on planets that are mostly likely to be able to support life – at least life as we know it.”

̽��ֱ��research was supported in part by the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

Reference:
Tereza Constantinou, Oliver Shorttle, and Paul B Rimmer. ‘A dry Venusian interior constrained by atmospheric chemistry.’ Nature Astronomy (2024). DOI: 10.1038/s41550-024-02414-5

A team of astronomers has found that Venus has never been habitable, despite decades of speculation that our closest planetary neighbour was once much more like Earth than it is today.

NASA/Jet Propulsion Laboratory-Caltech

View of surface of Venus

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A peek inside the box that could help solve a quantum mystery

sc604 — Tue, 19 Nov 2024 15:22:24 +0000

Appearing as ‘bumps’ in the data from high-energy experiments, these signals came to be known as short-lived ‘XYZ states.’ They defy the standard picture of particle behaviour and are a problem in contemporary physics, sparking several attempts to understand their mysterious nature.

But theorists at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility in Virginia, with colleagues from the ̽��ֱ�� of Cambridge, suggest the experimental data could be explained with fewer XYZ states, also called resonances, than currently claimed.

̽��ֱ��team used a branch of quantum physics to compute the energy levels, or mass, of particles containing a specific ‘flavour’ of the subatomic building blocks known as quarks. Quarks, along with gluons, a force-carrying particle, make up the Strong Force, one of the four fundamental forces of nature.

̽��ֱ��researchers found that multiple particle states sharing the same degree of spin – or angular momentum – are coupled, meaning only a single resonance exists at each spin channel. This new interpretation is contrary to several other theoretical and experimental studies.

̽��ֱ��researchers have presented their results in a pair of companion papers published for the international Hadron Spectrum Collaboration (HadSpec) in Physical Review Letters and Physical Review D. ̽��ֱ��work could also provide clues about an enigmatic particle: X(3872).

̽��ֱ��charm quark, one of six quark ‘flavours’, was first observed experimentally in 1974. It was discovered alongside its antimatter counterpart, the anticharm, and particles paired this way are part of an energy region called ‘charmonium.’

In 2003, Japanese researchers discovered a new charmonium candidate dubbed X(3872): a short-lived particle state that appears to defy the present quark model.

“X(3872) is now more than 20 years old, and we still haven’t obtained a clear, simple explanation that everyone can get behind,” said lead author Dr David Wilson from Cambridge’s Department of Applied Mathematics and Theoretical Physics (DAMTP).

Thanks to the power of modern particle accelerators, scientists have detected a hodgepodge of exotic charmonium candidate states over the past two decades.

“High-energy experiments started seeing bumps, interpreted as new particles, almost everywhere they looked,” said co-author Professor Jozef Dudek from William & Mary. “And very few of these states agreed with the model that came before.”

But now, by creating a tiny virtual ‘box’ to simulate quark behaviour, the researchers discovered that several supposed XYZ particles might actually be just one particle seen in different ways. This could help simplify the confusing jumble of data scientists have collected over the years.

Despite the tiny volumes they were working with, the team required enormous computing power to simulate all the possible behaviours and masses of quarks.

̽��ֱ��researchers used supercomputers at Cambridge and the Jefferson Lab to infer all the possible ways in which mesons – made of a quark and its antimatter counterpart – could decay. To do this, they had to relate the results from their tiny virtual box to what would happen in a nearly infinite volume – that is, the size of the universe.

“In our calculations, unlike experiment, you can't just fire in two particles and measure two particles coming out,” said Wilson. “You have to simultaneously calculate all possible final states, because quantum mechanics will find those for you.”

̽��ֱ��results can be understood in terms of just a single short-lived particle whose appearance could differ depending upon which possible decay state it is observed in.

“We're trying to simplify the picture as much as possible, using fundamental theory with the best methods available,” said Wilson. “Our goal is to disentangle what has been seen in experiments.”

Now that the team has proved this type of calculation is feasible, they are ready to apply it to the mysterious particle X(3872).

“ ̽��ֱ��origin of X(3872) is an open question,” said Wilson. “It appears very close to a threshold, which could be accidental or a key part of the story. This is one thing we will look at very soon."

Professor Christopher Thomas, also from DAMTP, is a member of the Hadron Spectrum Collaboration, and is a co-author on the current studies. Wilson’s contribution was made possible in part by an eight-year fellowship with the Royal Society. ̽��ֱ��research was also supported in part by the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI). Many of the calculations for this study were carried out with the support of the Cambridge Centre for Data Driven Discovery (CSD3) and DiRAC high-performance computing facilities in Cambridge, managed by Cambridge’s Research Computing Services division.

Reference:
David J. Wilson et al. ‘Scalar and Tensor Charmonium Resonances in Coupled-Channel Scattering from Lattice QCD.’ Physical Review Letters (2024). DOI: 10.1103/PhysRevLett.132.241901

David J. Wilson et al. ‘Charmonium xc0 and xc2 resonances in coupled-channel scattering from lattice QCD.’ Physical Review D (2024). DOI: 10.1103/PhysRevD.109.114503

Adapted from a Jefferson Lab story.

An elusive particle that first formed in the hot, dense early universe has puzzled physicists for decades. Following its discovery in 2003, scientists began observing a slew of other strange objects tied to the millionths of a second after the Big Bang.

gremlin via Getty Images

Abstract colourful lines

Yes

Mission to map the dark Universe sets off on space journey

sc604 — Sat, 01 Jul 2023 15:16:27 +0000

̽��ֱ��Euclid space telescope will map the 'dark Universe' by observing billions of galaxies out to 10 billion light-years, across more than a third of the sky, to gather data on how its structure has formed over its cosmic history.

Led by the European Space Agency (ESA) and a consortium of 2,000 scientists, including from the ̽��ֱ�� of Cambridge, Euclid will spend six years venturing through space with two scientific instruments: a UK-built visible imager (VIS) that will become one of the largest cameras ever sent into space, and a near-infrared spectrometer and photometer, developed in France. ̽��ֱ��mission is supported by funding from the UK Space Agency.

“Watching the launch of Euclid, I feel inspired by the years of hard work from thousands of people that go into space science missions, and the fundamental importance of discovery – how we set out to understand and explore the Universe,” said Chief Executive of the UK Space Agency, Dr Paul Bate. “ ̽��ֱ��UK Space Agency’s investment in Euclid has supported world-class science on this journey, from the development of the ground segment to the build of the crucial visible imager instrument, which will help humanity begin to uncover the mysteries of dark matter and dark energy.”

Euclid took off on board a SpaceX spacecraft from Cape Canaveral in Florida at 4.11pm (BST) on 1 July.

Cambridge’s Institute of Astronomy team has been involved in Euclid since 2010, supporting development of the astrometric calibration pipeline for the optical image data from Euclid, ensuring that the positions of the billions of sources to be imaged by Euclid can be determined to exquisite accuracy.

“Dark energy and dark matter fundamentally govern the formation and evolution of our Universe,” said Dr Nicholas Walton from the Institute of Astronomy. “ ̽��ֱ��Euclid mission will finally uncover the mysteries of how these ‘dark’ forces have shaped the cosmos that we see today, from life here on Earth, to our Sun, our Milky Way, our nearby galaxy neighbours, and the wider Universe beyond.”

̽��ֱ��Science and Technology Facilities Council (STFC) also contributed to design and development work on Euclid instrumentation and provided funding to UK astronomy teams who will analyse the data returned from the mission about the physics responsible for the observed accelerated expansion of the Universe.

“This is a fantastic example of close collaboration between scientists, engineers, technicians, and astronomers across Europe working together to tackle some of the biggest questions in science,” said Mark Thomson, Executive Chair at STFC.

UK Space Agency funding for the Euclid mission is divided between teams at ̽��ֱ�� College London, ̽��ֱ��Open ̽��ֱ��, ̽��ֱ�� of Cambridge, ̽��ֱ�� of Edinburgh, ̽��ֱ�� of Oxford, ̽��ֱ�� of Portsmouth and Durham ̽��ֱ��.

̽��ֱ��wider Euclid Consortium includes experts from 300 organisations across 13 European countries, the US, Canada and Japan.

A European mission to explore how gravity, dark energy and dark matter shaped the evolution of the Universe soared into space from Cape Canaveral on 1 July.

̽��ֱ��Euclid mission will finally uncover the mysteries of how these ‘dark’ forces have shaped the cosmos that we see today, from life here on Earth, to our Sun, our Milky Way, our nearby galaxy neighbours, and the wider Universe beyond

Nicholas Walton

ESA

Last glimpse of Euclid on Earth

̽��ֱ��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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Astronomers observe light bending around an isolated white dwarf

sc604 — Thu, 02 Feb 2023 08:08:58 +0000

Astronomers have directly measured the mass of a dead star using an effect known as gravitational microlensing, first predicted by Einstein in his General Theory of Relativity, and first observed by two Cambridge astronomers 100 years ago.

UK-led robotic sky scanner reveals its first galactic fingerprint

sc604 — Mon, 12 Dec 2022 09:05:03 +0000

̽��ֱ��spectra provide a first glimpse of the sky from the WHT Enhanced Area Velocity Explorer (WEAVE) – a unique upgrade to the William Herschel Telescope (WHT) in La Palma on the Canary Islands.

After its integration into the WHT last year, WEAVE has now begun its on-sky commissioning phase, ready to reveal more than 12 million spectra of stars and galaxies over the next five years.

̽��ֱ��Science and Technology Facilities Council (STFC) is one of the key partners in the operation of the WHT. Data processing, analysis and archiving for WEAVE is led by astronomers from the ̽��ֱ�� of Cambridge, with support from the IAC in Spain and INAF in Italy.

Understanding the Universe through spectra

Spectroscopy is an essential element in an astronomer’s toolbox. Analysing light detected with a telescope reveals useful scientific information, such as the speed of the object observed, the atoms it is made of and its temperature.

If an image tells us what an astronomical object looks like, its spectrum tells us what it is.

First galactic spectra with WEAVE

A galactic spectrum is the combination of spectra from the millions of stars in an observed galaxy. Studying the features of a galaxy spectrum allows astronomers to understand what types of stars the galaxy contains, and the relative abundances of each type of star. This tells us about how the galaxy formed and changed over time.

First-light observations with WEAVE were carried out with the large integral-field unit (LIFU) fibre bundle, one of WEAVE's three fibre systems. ̽��ֱ��team observed the heart of the galaxy group Stephan’s Quintet, a group of five interacting galaxies.

̽��ֱ��instrument was aimed at NGC 7318a and NGC 7318b, a pair of galaxies at the centre of a major galaxy collision 280 million light-years from Earth in the constellation Pegasus.

“ ̽��ֱ��wealth of complexity revealed in this way by a single detailed observation of this pair of nearby galaxies provides insights into the interpretation of the many millions of spectra that WEAVE will obtain from galaxies in the distant Universe and provides an excellent illustration of the power and flexibility of the WEAVE facility,” said Professor Gavin Dalton from the ̽��ֱ�� of Oxford.

̽��ֱ��WEAVE LIFU (large integral-field unit) measures separate spectra for 547 different regions in and around the two galaxies, recording the colours of their light from the ultraviolet to the near-infrared.

These spectra reveal the motions of stars and gas, the chemical composition of the stars, the temperatures and densities of the gas clouds, and more. This data will help astronomers learn how galaxy collisions transform the galaxies in the group.

“Without even breaking a sweat, WEAVE has provided us with an unprecedented glimpse into the dance of this enigmatic group of galaxies,” said Dr David Murphy from Cambridge’s Institute of Astronomy, lead of spectroscopic pipeline development for WEAVE. “This exciting initial release provides a snapshot of the various ways the instrument can provide insights into the universe. Coupled with our rapid-response data-processing pipelines, WEAVE will advance cutting-edge research ranging from the complex chemical fingerprint of our galactic neighbourhood to the very structure and fabric of our universe.”

“Our advanced analysis pipeline consists of a chain of more than 20 state-of-art modules developed to analyse a wide range of astronomical targets, from newly born hot stars to quasars,” said Dr Alireza Molaeinezhad from Cambridge’s Institute of Astronomy, Lead developer of the Advanced Processing System. “Using this pipeline on the phenomenal first-light data is like wearing 3D-glasses to watch the cosmic dance of galaxies in this system.”

Eight surveys using WEAVE

In the coming five years, the ING (Isaac Newton Group of Telescopes) will assign 70% of the time available on the WHT to eight major surveys with WEAVE, selected out of those proposed by the astronomical communities of the partner countries. All these surveys require spectra of up to millions of individual stars and galaxies, a goal now obtainable thanks to WEAVE’s ability to observe almost 1000 objects at a time.

Over 500 astronomers from across Europe have organized these eight surveys, covering studies of stellar evolution, Milky Way science, galaxy evolution and cosmology. WEAVE will study galaxies near and far to learn the history of their growth, and will obtain millions of spectra of stars in the Milky Way.

“This first light event is a milestone for both the international and UK astronomy communities: WEAVE will provide spectra of millions of stars and galaxies over the next five years,” said Professor Mark Thomson, STFC Executive Chair. “After ten years in development, WEAVE will now finally offer astronomers a new eye to the sky to help them answer questions such as what is dark matter and how did stars form in distant galaxies?”

“These wonderful first light images demonstrate the power of WEAVE to unravel the intricate chemo-dynamical processes at work in this galaxy system," said Dr Nicholas Walton from the Institute of Astronomy and lead of the WEAVE data analysis system development team. " ̽��ֱ��analysis of this data, from one of the many observational modes of WEAVE, has used our state-of-the-art science pipelines. We are now ready to handle the nightly data from WEAVE as it embarks on its main science surveys."

̽��ֱ��Isaac Newton Group of Telescopes (ING) is operated on behalf of the STFC in the UK, the Nederlanse Organisatie voor Wetenschappelijk Onderzoek (NWO) in ̽��ֱ��Netherlands, and the Instituto de Astrofísica de Canarias (IAC) in Spain.

Adapted from an STFC press release.

A major telescope upgrade has peered through to the distant Universe to reveal the spectra of a pair of galaxies 280 million light years away from Earth.

Without even breaking a sweat, WEAVE has provided us with an unprecedented glimpse into the dance of this enigmatic group of galaxies

David Murphy

ING

Blue, green and red colours, according to velocities derived from the WEAVE spectra, are overlaid on a composite image of Stephan’s Quintet, featuring galaxy star light (CFH telescope), and X-ray emission of hot gas (blue vertical band, Chandra X-ray)

̽��ֱ��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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Non-detection of key signal allows astronomers to determine what the first galaxies were – and weren’t – like

sc604 — Mon, 28 Nov 2022 16:00:00 +0000

Using data from India’s SARAS3 radio telescope, researchers led by the ̽��ֱ�� of Cambridge were able to look at the very early Universe – just 200 million years after the Big Bang – and place limits on the mass and energy output of the first stars and galaxies.

Counterintuitively, the researchers were able to place these limits on the earliest galaxies by not finding the signal they had been looking for, known as the 21-centimetre hydrogen line.

This non-detection allowed the researchers to make other determinations about the cosmic dawn, placing restraints on the first galaxies, and enabling them to rule out scenarios including galaxies that were inefficient heaters of cosmic gas and efficient producers of radio emissions.

While we cannot yet directly observe these early galaxies, the results, reported in the journal Nature Astronomy, represent an important step in understanding how our Universe transitioned from mostly empty to one full of stars.

Understanding the early Universe, when the first stars and galaxies formed, is one of the major goals of new observatories. ̽��ֱ��results obtained using the SARAS3 data are a proof-of-concept study that paves the way to understanding this period in the development of the Universe.

̽��ֱ��SKA project – involving two next-generation telescopes due to be completed by the end of the decade – will likely be able to make images of the early Universe, but for current telescopes, the challenge is to detect the cosmological signal of the first stars re-radiated by thick hydrogen clouds.

This signal is known as the 21-centimetre line – a radio signal produced by hydrogen atoms in the early Universe. Unlike the recently launched JWST, which will be able to directly image individual galaxies in the early Universe, studies of the 21-centimetre line, made with radio telescopes such as the Cambridge-led REACH (Radio Experiment for the Analysis of Cosmic Hydrogen), can tell us about entire populations of even earlier galaxies. ̽��ֱ��first results are expected from REACH early in 2023.

To detect the 21-centimetre line, astronomers look for a radio signal produced by hydrogen atoms in the early Universe, affected by light from the first stars and the radiation behind the hydrogen fog. Earlier this year, the same researchers developed a method that they say will allow them to see through the fog of the early universe and detect light from the first stars. Some of these techniques have been already put to practice in the current study.

In 2018, another research group operating the EDGES experiment published a result that hinted at a possible detection of this earliest light. ̽��ֱ��reported signal was unusually strong compared to what is expected in the simplest astrophysical picture of the early Universe. Recently, the SARAS3 data disputed this detection: the EDGES result is still awaiting confirmation from independent observations.

In a re-analysis of the SARAS3 data, the Cambridge-led team tested a variety of astrophysical scenarios which could potentially explain the EDGES result, but they did not find a corresponding signal. Instead, the team was able to place some limits on properties of the first stars and galaxies.

̽��ֱ��results of the SARAS3 analysis are the first time that radio observations of the averaged 21-centimetre line have been able to provide an insight to the properties of the first galaxies in the form of limits of their main physical properties.

Working with collaborators in India, Australia and Israel, the Cambridge team used data from the SARAS3 experiment to look for signals from cosmic dawn, when the first galaxies formed. Using statistical modelling techniques, the researchers were not able to find a signal in the SARAS3 data.

"We were looking for a signal with a certain amplitude,” said Harry Bevins, a PhD student from Cambridge’s Cavendish Laboratory and the paper’s lead author. “But by not finding that signal, we can put a limit on its depth. That, in turn, begins to inform us about how bright the first galaxies were.”

“Our analysis showed that the hydrogen signal can inform us about the population of first stars and galaxies,” said co-lead author Dr Anastasia Fialkov from Cambridge’s Institute of Astronomy. “Our analysis places limits on some of the key properties of the first sources of light including the masses of the earliest galaxies and the efficiency with which these galaxies can form stars. We also address the question of how efficiently these sources emit X-ray, radio and ultraviolet radiation.”

“This is an early step for us in what we hope will be a decade of discoveries about how the Universe transitioned from darkness and emptiness to the complex realm of stars, galaxies and other celestial objects we can see from Earth today,” said Dr Eloy de Lera Acedo from Cambridge’s Cavendish Laboratory, who co-led the research.

̽��ֱ��observational study, the first of its kind in many respects, excludes scenarios in which the earliest galaxies were both more than a thousand times as bright as present galaxies in their radio-band emission and were poor heaters of hydrogen gas.

“Our data also reveals something which has been hinted at before, which is that the first stars and galaxies could have had a measurable contribution to the background radiation that appeared as a result of the Big Bang and which has been travelling towards us ever since,” said de Lera Acedo, “We are also establishing a limit to that contribution.”

“It’s amazing to be able to look so far back in time – to just 200 million years after the Big Bang- and be able to learn about the early Universe,” said Bevins.

̽��ֱ��research was supported in part by the Science and Technology Facilities Council (STFC), part of UK Research & Innovation (UKRI), and the Royal Society. ̽��ֱ��Cambridge authors are all members of the Kavli Institute for Cosmology in Cambridge.

Reference:
H T J Bevins et al. ‘Astrophysical constraints from the SARAS 3 non-detection of the cosmic dawn sky-averaged 21-cm signal.’ Nature Astronomy (2022). DOI: 10.1038/s41550-022-01825-6

Researchers have been able to make some key determinations about the first galaxies to exist, in one of the first astrophysical studies of the period in the early Universe when the first stars and galaxies formed, known as the cosmic dawn.

This is an early step for us in what we hope will be a decade of discoveries about how the Universe transitioned from darkness and emptiness to the complex realm of stars and galaxies we can see today

Eloy de Lera Acedo

NASA Goddard

Early galaxies capture by the NASA/ESA Hubble Telescope

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No signs (yet) of life on Venus

sc604 — Tue, 14 Jun 2022 15:00:00 +0000

Researchers from the ̽��ֱ�� of Cambridge used a combination of biochemistry and atmospheric chemistry to test the ‘life in the clouds’ hypothesis, which astronomers have speculated about for decades, and found that life cannot explain the composition of the Venusian atmosphere.

Any life form in sufficient abundance is expected to leave chemical fingerprints on a planet’s atmosphere as it consumes food and expels waste. However, the Cambridge researchers found no evidence of these fingerprints on Venus.

Even if Venus is devoid of life, the researchers say their results, reported in the journal Nature Communications, could be useful for studying the atmospheres of similar planets throughout the galaxy, and the eventual detection of life outside our Solar System.

“We’ve spent the past two years trying to explain the weird sulphur chemistry we see in the clouds of Venus,” said co-author Dr Paul Rimmer from Cambridge’s Department of Earth Sciences. “Life is pretty good at weird chemistry, so we’ve been studying whether there’s a way to make life a potential explanation for what we see.”

̽��ֱ��researchers used a combination of atmospheric and biochemical models to study the chemical reactions that are expected to occur, given the known sources of chemical energy in Venus’s atmosphere.

“We looked at the sulphur-based ‘food’ available in the Venusian atmosphere – it’s not anything you or I would want to eat, but it is the main available energy source,” said Sean Jordan from Cambridge’s Institute of Astronomy, the paper’s first author. “If that food is being consumed by life, we should see evidence of that through specific chemicals being lost and gained in the atmosphere.”

̽��ֱ��models looked at a particular feature of the Venusian atmosphere – the abundance of sulphur dioxide (SO2). On Earth, most SO2 in the atmosphere comes from volcanic emissions. On Venus, there are high levels of SO2 lower in the clouds, but it somehow gets ‘sucked out’ of the atmosphere at higher altitudes.

“If life is present, it must be affecting the atmospheric chemistry,” said co-author Dr Oliver Shorttle from Cambridge’s Department of Earth Sciences and Institute of Astronomy. “Could life be the reason that SO2 levels on Venus get reduced so much?”

̽��ֱ��models, developed by Jordan, include a list of metabolic reactions that the life forms would carry out in order to get their ‘food’, and the waste by-products. ̽��ֱ��researchers ran the model to see if the reduction in SO2 levels could be explained by these metabolic reactions.

They found that the metabolic reactions can result in a drop in SO2 levels, but only by producing other molecules in very large amounts that aren’t seen. ̽��ֱ��results set a hard limit on how much life could exist on Venus without blowing apart our understanding of how chemical reactions work in planetary atmospheres.

“If life was responsible for the SO2 levels we see on Venus, it would also break everything we know about Venus’s atmospheric chemistry,” said Jordan. “We wanted life to be a potential explanation, but when we ran the models, it isn’t a viable solution. But if life isn’t responsible for what we see on Venus, it’s still a problem to be solved – there’s lots of strange chemistry to follow up on.”

Although there’s no evidence of sulphur-eating life hiding in the clouds of Venus, the researchers say their method of analysing atmospheric signatures will be valuable when JWST, the successor to the Hubble Telescope, begins returning images of other planetary systems later this year. Some of the sulphur molecules in the current study are easy to see with JWST, so learning more about the chemical behaviour of our next-door neighbour could help scientists figure out similar planets across the galaxy.

“To understand why some planets are alive, we need to understand why other planets are dead,” said Shorttle. “If life somehow managed to sneak into the Venusian clouds, it would totally change how we search for chemical signs of life on other planets.”

“Even if ‘our’ Venus is dead, it’s possible that Venus-like planets in other systems could host life,” said Rimmer, who is also affiliated with Cambridge’s Cavendish Laboratory. “We can take what we’ve learned here and apply it to exoplanetary systems – this is just the beginning.”

̽��ֱ��research was funded by the Simons Foundation and the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

Reference:
Sean Jordan, Oliver Shorttle and Paul B Rimmer. ‘Proposed energy-metabolisms cannot explain the atmospheric chemistry of Venus.’ Nature Communications (2022). DOI: 10.1038/s41467-022-30804-8

̽��ֱ��unusual behaviour of sulphur in Venus’ atmosphere cannot be explained by an ‘aerial’ form of extra-terrestrial life, according to a new study.

Even if ‘our’ Venus is dead, it’s possible that Venus-like planets in other systems could host life

Paul Rimmer

NASA/JPL-Caltech

Venus from Mariner 10

Yes

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