̽��ֱ�� of Cambridge - astrophysics

Strongest hints yet of biological activity outside the solar system

sc604 — Thu, 17 Apr 2025 04:09:34 +0000

Astronomers have detected the most promising signs yet of a possible biosignature outside the solar system, although they remain cautious.

Scientists reveal structure of 74 exocomet belts orbiting nearby stars

Anonymous — Fri, 17 Jan 2025 08:00:00 +0000

̽��ֱ��crystal-clear images show light being emitted from these millimetre-sized pebbles within the belts that orbit 74 nearby stars of a wide variety of ages – from those that are just emerging to those in more mature systems like our own Solar System.

̽��ֱ��REASONS (REsolved ALMA and SMA Observations of Nearby Stars) study, led by Trinity College Dublin and involving researchers from the ̽��ֱ�� of Cambridge, is a milestone in the study of exocometary belts because its images and analyses reveal where the pebbles, and the exocomets, are located. They are typically tens to hundreds of astronomical units (the distance from Earth to the Sun) from their central star.

In these regions, it is so cold (-250 to -150 degrees Celsius) that most compounds are frozen as ice on the exocomets. What the researchers are therefore observing is where the ice reservoirs of planetary systems are located. REASONS is the first programme to unveil the structure of these belts for a large sample of 74 exoplanetary systems. ̽��ֱ��results are reported in the journal Astronomy & Astrophysics.

This study used both the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile and the Submillimeter Array (SMA) in Hawai‘i to produce the images that have provided more information on populations of exocomets than ever before. Both telescope arrays observe electromagnetic radiation at millimetre and submillimetre wavelengths.

“Exocomets are boulders of rock and ice, at least one kilometre in size, which smash together within these belts to produce the pebbles that we observe here with the ALMA and SMA arrays of telescopes,” said lead author Luca Matrà from Trinity College Dublin. “Exocometary belts are found in at least 20% of planetary systems, including our own Solar System.”

“ ̽��ֱ��images reveal a remarkable diversity in the structure of belts,” said co-author Dr Sebastián Marino from the ̽��ֱ�� of Exeter. “Some are narrow rings, as in the canonical picture of a ‘belt’ like our Solar System’s Edgeworth-Kuiper belt. But a larger number of them are wide, and probably better described as ‘disks’ rather than rings.”

Some systems have multiple rings/disks, some of which are eccentric, providing evidence that yet undetectable planets are present and their gravity affects the distribution of pebbles in these systems.

“ ̽��ֱ��power of a large study like REASONS is in revealing population-wide properties and trends,” said Matrà.

For example, the study confirmed that the number of pebbles decreases for older planetary systems as belts run out of larger exocomets smashing together, but showed for the first time that this decrease in pebbles is faster if the belt is closer to the central star. It also indirectly showed – through the belts’ vertical thickness – that objects as large as 140 km across and even Moon-size objects are likely present in these belts.

“We have been studying exocometary belts for decades, but until now only a handful had been imaged,” said co-author Professor Mark Wyatt from Cambridge’s Institute of Astronomy. “This is the largest collection of such images and demonstrates that we already have the capabilities to probe the structures of the planetary systems orbiting a large fraction of the stars near to the Sun.”

“Arrays like the ALMA and SMA used in this work are extraordinary tools that are continuing to give us incredible new insights into the universe and its workings,” said co-author Dr David Wilner from the Center for Astrophysics | Harvard & Smithsonian “ ̽��ֱ��REASONS survey required a large community effort and has an incredible legacy value, with multiple potential pathways for future investigation.”

Reference:
L. Matrà et al. ‘REsolved ALMA and SMA Observations of Nearby Stars. REASONS: A population of 74 resolved planetesimal belts at millimetre wavelengths.’ Astronomy & Astrophysics (2025). DOI: 10.1051/0004-6361/202451397

Adapted from a Trinity College Dublin media release.

An international team of astrophysicists has imaged a large number of exocomet belts around nearby stars, and the tiny pebbles within them.

Luca Matra, Trinity College Dublin, and colleagues

Millimetre continuum images for the REASONS resolved sample of 74 exocomet belts

̽��ֱ��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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Early universe crackled with bursts of star formation, Webb Telescope shows

sc604 — Tue, 06 Jun 2023 00:52:41 +0000

One of the largest programmes in Webb’s first year of science is the JWST Advanced Deep Extragalactic Survey, or JADES, which will devote about 32 days of telescope time to uncover and characterise faint, distant galaxies. While data is still coming in, JADES has already discovered hundreds of galaxies that existed when the universe was less than 600 million years old. ̽��ֱ��international team, including researchers from the ̽��ֱ�� of Cambridge, also has identified galaxies sparkling with a multitude of young, hot stars.

̽��ֱ��extragalactic research group at the Cavendish Laboratory co-led by Professor Roberto Maiolino and Dr Sandro Tacchella is playing a leadership role in JADES, which is a partnership between the science team of NIRCam — JWST’s primary imager — and NIRSpec — JWST’s primary spectrograph.

In the autumn of 2022, JADES took deep imaging and spectroscopy in and around the iconic Hubble Ultra Deep Field. ̽��ֱ��JADES imaging is deep, extends further into the infrared, and covers a wider area than any previous imaging with the Hubble Space Telescope. Results based on this data, which have not yet been peer-reviewed, are being reported at the 242nd meeting of the American Astronomical Society in Albuquerque, New Mexico.

“With JADES, we want to answer a lot of questions, like: How did the earliest galaxies assemble themselves? How fast did they form stars? Why do some galaxies stop forming stars?” said Marcia Rieke of the ̽��ֱ�� of Arizona, co-lead of the JADES programme.

For hundreds of millions of years after the big bang, the universe was filled with a gaseous fog. By one billion years after the big bang, the fog had cleared and the universe became transparent, a process known as reionisation. Scientists have debated whether active, supermassive black holes or galaxies full of hot, young stars were the primary cause of reionisation.

As part of the JADES programme, researchers studied these galaxies to look for signatures of star formation – and found them in abundance. “Almost every single galaxy that we are finding shows these unusually strong emission line signatures indicating intense recent star formation. These early galaxies were very good at creating hot, massive stars,” said Ryan Endsley from the ̽��ֱ�� of Texas at Austin.

These bright, massive stars pumped out ultraviolet light, which transformed surrounding gas from opaque to transparent by ionising the atoms, removing electrons from their nuclei. Since these early galaxies had such a large population of hot, massive stars, they may have been the main driver of the reionisation process. ̽��ֱ��later reuniting of the electrons and nuclei produces distinctively strong emission lines.

̽��ֱ��team also found evidence that these young galaxies underwent periods of rapid star formation interspersed with quiet periods where fewer stars formed. These fits and starts may have occurred as galaxies captured clumps of the gaseous raw materials needed to form stars. Alternatively, since massive stars quickly explode, they may have injected energy into the surrounding environment periodically, preventing gas from condensing to form new stars.

Another JADES result released today concerns the structural evolution of galaxies. ̽��ֱ��team used imaging and spectroscopy data to tackle a key unknown in extragalactic astrophysics, which is how the structural diversity of galaxies we observe today came to be.

̽��ֱ��team discovered a galaxy in the infant universe – just 700 million years after the big bang – but with the structure of a far more mature galaxy. ̽��ֱ��galaxy is 100 times less massive than the Milky Way, but it is highly compact. Most of the young stars of this galaxy are in the outskirts, indicating that this galaxy is growing from the inside out.

“I was surprised to find such a compact galaxy this early in the universe,” said Tacchella, from Cambridge’s Cavendish Laboratory and Kavli Institute for Cosmology. “I’m excited that the telescope works so well, allowing us to do such detailed measurements of galaxies that are so distant.”

Another element of the JADES programme involves the search for the earliest galaxies that existed when the universe was less than 400 million years old. By studying these galaxies, astronomers can explore how star formation in the early years after the big bang was different from what is seen in current times.

̽��ֱ��light from faraway galaxies is stretched to longer wavelengths and redder colours by the expansion of the universe – a phenomenon called redshift. By measuring a galaxy’s redshift, astronomers can learn how far away it is and, therefore, when it existed in the early universe. Before Webb, there were only a few dozen galaxies observed above a redshift of 8, when the universe was younger than 650 million years old, but JADES has now uncovered nearly a thousand of these extremely distant galaxies.

̽��ֱ��gold standard for determining redshift involves looking at a galaxy’s spectrum, which measures its brightness at closely spaced wavelengths. But a good approximation can be determined by taking photos of a galaxy using filters that each cover a narrow band of colours to get a handful of brightness measurements. In this way, researchers can determine estimates for the distances of many thousands of galaxies at once.

Kevin Hainline of the ̽��ֱ�� of Arizona in Tucson and his colleagues used Webb’s NIRCam (Near-Infrared Camera) instrument to obtain these measurements, called photometric redshifts, and identified more than 700 candidate galaxies that existed when the universe was between 370 million and 650 million years old. ̽��ֱ��sheer number of these galaxies was far beyond predictions from observations made before Webb’s launch. ̽��ֱ��observatory’s resolution and sensitivity are allowing astronomers to get a better view of these distant galaxies than ever before.

“Previously, the earliest galaxies we could see just looked like little smudges. And yet those smudges represent millions or even billions of stars at the beginning of the universe,” said Hainline. “Now, we can see that some of them are actually extended objects with visible structure. We can see groupings of stars being born only a few hundred million years after the beginning of time.”

“We’re finding star formation in the early universe is much more complicated than we thought,” said Rieke.

Adapted from a NASA press release.

Among the most fundamental questions in astronomy is: How did the first stars and galaxies form? ̽��ֱ��James Webb Space Telescope (JWST), a partnership between NASA, the European Space Agency and the Canadian Space Agency, is already providing new insights into this question.

I’m excited that the telescope works so well, allowing us to do such detailed measurements of galaxies that are so distant

Sandro Tacchella

NASA, ESA, CSA, Brant Robertson, Ben Johnson, Sandro Tacchella, Marcia Rieke, Daniel Eisenstein

This infrared image from NASA’s James Webb Space Telescope (JWST) was taken for the JWST Advanced Deep Extragalactic Survey, or JADES, programme.

̽��ֱ��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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Public Domain

Humanity’s quest to discover the origins of life in the universe

sc604 — Wed, 08 Mar 2023 17:10:32 +0000

For thousands of years, humanity and science have contemplated the origins of life in the Universe. While today’s scientists are well-equipped with innovative technologies, humanity has a long way to go before we fully understand the fundamental aspects of what life is and how it forms.

“We are living in an extraordinary moment in history,” said Professor Didier Queloz, who directs the Leverhulme Centre for Life in the Universe at Cambridge and ETH Zurich’s Centre for Origin and Prevalence of Life. While still a doctoral student, Queloz was the first to discover an exoplanet – a planet orbiting a star other than our Sun. ̽��ֱ��discovery led to him being awarded the 2019 Nobel Prize in Physics.

In the three decades since Queloz’s discovery, scientists have discovered more than 5,000 exoplanets. Trillions more are predicted to exist within our Milky Way galaxy alone. Each exoplanet discovery raises more questions about how and why life emerged on Earth and whether it exists elsewhere in the universe.

Technological advancements, such as the James Webb Space Telescope and interplanetary missions to Mars, give scientists access to huge volumes of new observations and data. Sifting through all this information to understand the emergence of life in the universe will take a big, multidisciplinary network.

In collaboration with chemist and fellow Nobel Laureate Jack Szostak and astronomer Dimitar Sasselov, Queloz announced the formation of such a network at the American Association for the Advancement of Science (AAAS) meeting in Washington, DC. ̽��ֱ��Origins Federation brings together researchers studying the origins of life at Cambridge, ETH Zurich, Harvard ̽��ֱ��, and ̽��ֱ�� ̽��ֱ�� of Chicago.

Together, Federation scientists will explore the chemical and physical processes of living organisms and environmental conditions hospitable to supporting life on other planets. “ ̽��ֱ��Origins Federation builds upon a long-standing collegial relationship strengthened through a shared collaboration in a recently completed project with the Simons Foundation,” said Queloz.

These collaborations support the work of researchers like Dr Emily Mitchell from Cambridge's Department of Zoology. Mitchell is co-director of Cambridge’s Leverhulme Centre for Life in the Universe and an ecological time traveller. She uses field-based laser-scanning and statistical mathematical ecology on 580-million-year-old fossils of deep-sea organisms to determine the driving factors that influence the macro-evolutionary patterns of life on Earth.

Speaking at AAAS, Mitchell took participants back to four billion years ago when Earth’s early atmosphere - devoid of oxygen and steeped in methane – showed its first signs of microbial life. She spoke about how life survives in extreme environments and then evolves offering potential astrobiological insights into the origins of life elsewhere in the universe.

“As we begin to investigate other planets through the Mars missions, biosignatures could reveal whether or not the origin of life itself and its evolution on Earth is just a happy accident or part of the fundamental nature of the universe, with all its biological and ecological complexities,” said Mitchell.

̽��ֱ��founding centres of the Origins Federation are ̽��ֱ��Origins of Life Initiative (Harvard ̽��ֱ��), Centre for Origin and Prevalence of Life (ETH Zurich), the Center for the Origins of Life ( ̽��ֱ�� of Chicago), and the Leverhulme Centre for Life in the Universe ( ̽��ֱ�� of Cambridge).

̽��ֱ��Origins Federation will pursue scientific research topics of interest to its founding centres with a long-term perspective and common milestones. It will strive to establish a stable funding platform to create opportunities for creative and innovative ideas, and to enable young scientists to make a career in this new field. ̽��ֱ��Origins Federation is open to new members, both centres and individuals, and is committed to developing the mechanisms and structure to achieve that aim.

“ ̽��ֱ��pioneering work of Professor Queloz has allowed astronomers and physicists to make advances that were unthinkable only a few years ago, both in the discovery of planets which could host life and the development of techniques to study them,” said Professor Andy Parker, head of Cambridge's Cavendish Laboratory. “But now we need to bring the full range of our scientific understanding to bear in order to understand what life really is and whether it exists on these newly discovered planets. ̽��ֱ��Cavendish Laboratory is proud to host the Leverhulme Centre for Life in the Universe and to partner with the Origins Federation to lead this quest.”

Scientists from the ̽��ֱ�� of Cambridge, ETH Zurich, Harvard ̽��ֱ��, and the ̽��ֱ�� of Chicago have founded the Origins Federation, which will advance our understanding of the emergence and early evolution of life, and its place in the cosmos.

ETH Zurich/NASA

L-R: Emily Mitchell, Didier Queloz, Kate Adamal, Carl Zimmer

̽��ֱ��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

Yes

Licence type:

Public Domain

Can cosmic inflation be ruled out?

sc604 — Thu, 03 Nov 2022 11:59:51 +0000

̽��ֱ��astrophysicists, from the ̽��ֱ�� of Cambridge, the ̽��ֱ�� of Trento, and Harvard ̽��ֱ��, say that there is a clear, unambiguous signal in the cosmos that could eliminate inflation as a possibility. Their paper, published in ̽��ֱ��Astrophysical Journal Letters, argues that this signal – known as the cosmic graviton background (CGB) – can feasibly be detected, although it will be a massive technical and scientific challenge.

“Inflation was theorised to explain various fine-tuning challenges of the so-called hot Big Bang model,” said the paper’s first author Dr Sunny Vagnozzi, from Cambridge’s Kavli Institute for Cosmology, and who is now based at the ̽��ֱ�� of Trento. “It also explains the origin of structure in our Universe as a result of quantum fluctuations.

“However, the large flexibility displayed by possible models for cosmic inflation which span an unlimited landscape of cosmological outcomes raises concerns that cosmic inflation is not falsifiable, even if individual inflationary models can be ruled out. Is it possible in principle to test cosmic inflation in a model-independent way?”

Some scientists raised concerns about cosmic inflation in 2013, when the Planck satellite released its first measurements of the cosmic microwave background (CMB), the universe's oldest light.

“When the results from the Planck satellite were announced, they were held up as a confirmation of cosmic inflation,” said Professor Avi Loeb from Harvard ̽��ֱ��, Vagnozzi’s co-author on the current paper. “However, some of us argued that the results might be showing just the opposite.”

Along with Anna Ijjas and Paul Steinhardt, Loeb was one of those who argued that results from Planck showed that inflation posed more puzzles than it solved, and that it was time to consider new ideas about the beginnings of the universe, which, for instance, may have begun not with a bang but with a bounce from a previously contracting cosmos.

̽��ֱ��maps of the CMB released by Planck represent the earliest time in the universe we can ‘see’, 100 million years before the first stars formed. We cannot see farther.

“ ̽��ֱ��actual edge of the observable universe is at the distance that any signal could have travelled at the speed-of-light limit over the 13.8 billion years that elapsed since the birth of the Universe,” said Loeb. “As a result of the expansion of the universe, this edge is currently located 46.5 billion light years away. ̽��ֱ��spherical volume within this boundary is like an archaeological dig centred on us: the deeper we probe into it, the earlier is the layer of cosmic history that we uncover, all the way back to the Big Bang which represents our ultimate horizon. What lies beyond the horizon is unknown.”

In could be possible to dig even further into the universe’s beginnings by studying near-weightless particles known as neutrinos, which are the most abundant particles that have mass in the universe. ̽��ֱ��Universe allows neutrinos to travel freely without scattering from approximately a second after the Big Bang, when the temperature was ten billion degrees. “ ̽��ֱ��present-day universe must be filled with relic neutrinos from that time,” said Vagnozzi.

Vagnozzi and Loeb say we can go even further back, however, by tracing gravitons, particles that mediate the force of gravity.

“ ̽��ֱ��Universe was transparent to gravitons all the way back to the earliest instant traced by known physics, the Planck time: 10 to the power of -43 seconds, when the temperature was the highest conceivable: 10 to the power of 32 degrees,” said Loeb. “A proper understanding of what came before that requires a predictive theory of quantum gravity, which we do not possess.”

Vagnozzi and Loeb say that once the Universe allowed gravitons to travel freely without scattering, a relic background of thermal gravitational radiation with a temperature of slightly less than one degree above absolute zero should have been generated: the cosmic graviton background (CGB).

However, the Big Bang theory does not allow for the existence of the CGB, as it suggests that the exponential inflation of the newborn universe diluted relics such as the CGB to a point that they are undetectable. This can be turned into a test: if the CGB were detected, clearly this would rule out cosmic inflation, which does not allow for its existence.

Vagnozzi and Loeb argue that such a test is possible, and the CGB could in principle be detected in future. ̽��ֱ��CGB adds to the cosmic radiation budget, which otherwise includes microwave and neutrino backgrounds. It therefore affects the cosmic expansion rate of the early Universe at a level that is detectable by next-generation cosmological probes, which could provide the first indirect detection of the CGB.

However, to claim a definitive detection of the CGB, the ‘smoking gun’ would be the detection of a background of high-frequency gravitational waves peaking at frequencies around 100 GHz. This would be very hard to detect, and would require tremendous technological advances in gyrotron and superconducting magnets technology. Nevertheless, say the researchers, this signal may be within our reach in future.

Reference:
Sunny Vagnozzi and Abraham Loeb. ‘ ̽��ֱ��Challenge of Ruling Out Inflation via the Primordial Graviton Background.’ ̽��ֱ��Astrophysical Journal Letters (2022). DOI: 10.3847/2041-8213/ac9b0e

Adapted in part from a piece on Medium by Avi Loeb.

Astrophysicists say that cosmic inflation – a point in the Universe’s infancy when space-time expanded exponentially, and what physicists really refer to when they talk about the ‘Big Bang’ – can in principle be ruled out in an assumption-free way.

Is it possible in principle to test cosmic inflation in a model-independent way?

Sunny Vagnozzi

A Ijjas, PJ Steinhardt and A Loeb (Scientific American, February 2017)

Cosmic inflation is a popular scenario for the earliest phase in the evolution of the Universe

Yes

Hubble sees new atmosphere forming on a rocky exoplanet

sc604 — Thu, 11 Mar 2021 14:00:00 +0000

̽��ֱ��planet GJ 1132 b appears to have begun life as a gaseous world with a thick blanket of atmosphere. Starting out at several times the radius of Earth, this ‘sub-Neptune’ quickly lost its primordial hydrogen and helium atmosphere, which was stripped away by the intense radiation from its hot, young star. In a short period of time, it was reduced to a bare core about the size of Earth.

To the surprise of astronomers, new observations from Hubble have uncovered a secondary atmosphere that has replaced the planet’s first atmosphere. It is rich in hydrogen, hydrogen cyanide, methane and ammonia, and also has a hydrocarbon haze. Astronomers theorise that hydrogen from the original atmosphere was absorbed into the planet’s molten magma mantle and is now being slowly released by volcanism to form a new atmosphere. This second atmosphere, which continues to leak away into space, is continually being replenished from the reservoir of hydrogen in the mantle’s magma.

“This second atmosphere comes from the surface and interior of the planet, and so it is a window onto the geology of another world,” said team member Paul Rimmer from the ̽��ֱ�� of Cambridge. “A lot more work needs to be done to properly look through it, but the discovery of this window is of great importance.”

“We first thought that these highly radiated planets would be pretty boring because we believed that they lost their atmospheres,” said team member Raissa Estrela of the Jet Propulsion Laboratory at the California Institute of Technology in Pasadena, California, USA. “But we looked at existing observations of this planet with Hubble and realised that there is an atmosphere there.”

“How many terrestrial planets don’t begin as terrestrials? Some may start as sub-Neptunes, and they become terrestrials through a mechanism whereby light evaporates the primordial atmosphere. This process works early in a planet’s life, when the star is hotter,” said team leader Mark Swain of the Jet Propulsion Laboratory. “Then the star cools down and the planet’s just sitting there. So you’ve got this mechanism that can cook off the atmosphere in the first 100 million years, and then things settle down. And if you can regenerate the atmosphere, maybe you can keep it.”

In some ways, GJ 1132 b has various parallels to Earth, but in some ways, it is also very different. Both have similar densities, similar sizes, and similar ages, being about 4.5 billion years old. Both started with a hydrogen-dominated atmosphere, and both were hot before they cooled down. ̽��ֱ��team’s work even suggests that GJ 1132 b and Earth have similar atmospheric pressure at the surface.

However, the planets’ formation histories are profoundly different. Earth is not believed to be the surviving core of a sub-Neptune. And Earth orbits at a comfortable distance from our yellow dwarf Sun. GJ 1132 b is so close to its host red dwarf star that it completes an orbit the star once every day and a half. This extremely close proximity keeps GJ 1132 b tidally locked, showing the same face to its star at all times — just as our moon keeps one hemisphere permanently facing Earth.

“ ̽��ֱ��question is, what is keeping the mantle hot enough to remain liquid and power volcanism?” asked Swain. “This system is special because it has the opportunity for quite a lot of tidal heating.”

̽��ֱ��phenomenon of tidal heating occurs through friction, when energy from a planet’s orbit and rotation is dispersed as heat inside the planet. GJ 1132 b is in an elliptical orbit, and the tidal forces acting on it are strongest when it is closest to or farthest from its host star. At least one other planet in the host star’s system also exerts a gravitational pull on the planet. ̽��ֱ��consequences are that the planet is squeezed or stretched by this gravitational “pumping.” That tidal heating keeps the mantle liquid for a long time. A nearby example in our own Solar System is the Jovian moon, Io, which has continuous volcanism as a result of a tidal tug-of-war between Jupiter and the neighbouring Jovian moons.

̽��ֱ��team believes the crust of GJ 1132 b is extremely thin, perhaps only hundreds of feet thick. That’s much too feeble to support anything resembling volcanic mountains. Its flat terrain may also be cracked like an eggshell by tidal flexing. Hydrogen and other gases could be released through such cracks.

“This atmosphere, if it’s thin — meaning if it has a surface pressure similar to Earth — probably means you can see right down to the ground at infrared wavelengths. That means that if astronomers use the James Webb Space Telescope to observe this planet, there’s a possibility that they will see not the spectrum of the atmosphere, but rather the spectrum of the surface,” said Swain. “And if there are magma pools or volcanism going on, those areas will be hotter. That will generate more emission, and so they’ll potentially be looking at the actual geological activity — which is exciting!”

This result is significant because it gives exoplanet scientists a way to figure out something about a planet's geology from its atmosphere,” said Rimmer, who is affiliated both with Cambridge’s Cavendish Laboratory and Department of Earth Sciences. “It is also important for understanding where the rocky planets in our own Solar System — Mercury, Venus, Earth and Mars, fit into the bigger picture of comparative planetology, in terms of the availability of hydrogen versus oxygen in the atmosphere.”

Adapted from an ESA/JPL press release.

For the first time, scientists using the NASA/ESA Hubble Space Telescope have found evidence of volcanic activity reforming the atmosphere on a rocky planet around a distant star. ̽��ֱ��planet, GJ 1132 b, has a similar density, size, and age to Earth.

It is a window onto the geology of another world

Paul Rimmer

NASA, ESA, and R. Hurt (IPAC/Caltech)

Artist’s impression of the exoplanet GJ 1132 b

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Quantum projects launched to solve universe’s mysteries

sc604 — Wed, 13 Jan 2021 09:00:00 +0000

UK Research and Innovation (UKRI) is supporting seven projects with a £31 million investment to demonstrate how quantum technologies could solve some of the greatest mysteries in fundamental physics. Researchers from the ̽��ֱ�� of Cambridge have been awarded funding on four of the seven projects.

Just as quantum computing promises to revolutionise traditional computing, technologies such as quantum sensors have the potential to radically change our approach to understanding our universe.

̽��ֱ��projects are supported through the Quantum Technologies for Fundamental Physics programme, delivered by the Science and Technology Facilities Council (STFC) and the Engineering and Physical Sciences Research Council (EPSRC) as part of UKRI’s Strategic Priorities Fund. ̽��ֱ��programme is part of the National Quantum Technologies Programme.

AION: A UK Atom Interferometer Observatory and Network has been awarded £7.2 million in funding and will be led by Imperial College London. ̽��ֱ��project will develop and use technology based on quantum interference between atoms to detect ultra-light dark matter and sources of gravitational waves, such as collisions between massive black holes far away in the universe and violent processes in the very early universe. ̽��ֱ��team will design a 10m atom interferometer, preparing the construction of the instrument in Oxford and paving the way for larger-scale future experiments to be located in the UK. Members of the AION consortium will also contribute to MAGIS, a partner experiment in the US.

̽��ֱ��Cambridge team on AION is led by Professor Valerie Gibson and Dr Ulrich Schneider from the Cavendish Laboratory, alongside researchers from the Kavli Institute for Cosmology, the Institute of Astronomy and the Department of Applied Mathematics and Theoretical Physics. Dr Tiffany Harte will co-lead the development of the cold atom transport and final cooling sequences for AION, and Dr Jeremy Mitchell will co-lead the data readout and network capabilities for AION and MAGIS, and undertake data analysis and theoretical interpretation.

“This announcement from STFC to fund the AION project, which alongside some seed funding from the Kavli Foundation, will allow us to target key open questions in fundamental physics and bring new interdisciplinary research to the ̽��ֱ�� for the foreseeable future,” said Gibson.

“Every physical effect, known or unknown, leaves its fingerprint on the phase evolution of a coherent quantum system such as cold atoms; it only requires sufficiently sensitive detectors,” said Schneider. “We are excited to contribute our cold-atom technology to this interdisciplinary endeavour and to develop atom interferometry into a powerful detector for fundamental physics.”

̽��ֱ��Quantum Sensors for the Hidden Sector (QSHS) project, led by the ̽��ֱ�� of Sheffield, has been awarded £4.8 million in funding. ̽��ֱ��project aims to contribute to the search for axions, low-mass ‘hidden’ particles that are candidates to solve the mystery of dark matter. They will develop new quantum measurement technology for inclusion in the US ADMX experiment, which can then be used to search for axions in parts of our galaxy’s dark matter halo that have never been explored before.

“ ̽��ֱ��team will develop new electronic technology to a high level of sophistication and deploy it to search for the lowest-mass particles detected to date,” said Professor Stafford Withington from the Cavendish Laboratory, Co-Investigator and Senior Project Scientist on QSHS. “These particles are predicted to exist theoretically, but have not yet been discovered experimentally. Our ability to probe the particulate nature of the physical world with sensitivities that push at the limits imposed by quantum uncertainty will open up a new frontier in physics.

“This new window will allow physicists to explore the nature of physical reality at the most fundamental level, and it is extremely exciting that the UK will be playing a major international role in this new generation of science.”

Professor Withington is also involved in the Determination of Absolute Neutrino Mass using Quantum Technologies, which will be led by UCL. ̽��ֱ��project aims to harness recent breakthroughs in quantum technologies to solve one of the most important outstanding challenges in particle physics – determining the absolute mass of neutrinos. One of the universe’s most abundant particles neutrinos are a by-product of nuclear fusion within stars, therefore being key to our understanding of the processes within stars and the makeup of the universe. Moreover, knowing the value of the neutrino mass is critical to our understanding of the origin of matter and evolution of the universe. They are poorly understood however, and the researchers aim to develop pioneering new spectroscopy technology capable to precisely measure the mass of this elusive but important particle.

Professor Zoran Hadzibabic has received funding as part of the Quantum Simulators for Fundamental Physics project, led by the ̽��ֱ�� of Nottingham. ̽��ֱ��project aims to develop quantum simulators capable of providing insights into the physics of the very early universe and black holes. ̽��ֱ��goals include simulating aspects of quantum black holes and testing theories of the quantum vacuum that underpin ideas on the origin of the universe.

Researchers will use cutting-edge quantum technologies to transform our understanding of the universe and answer key questions such as the nature of dark matter and black holes.

NASA Goddard Space Flight Center

New Simulation Sheds Light on Spiraling Supermassive Black Holes

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