Catastrophically warm predictions are more plausible than we thought

Ecole Polytechnique Fédérale de Lausanne

What will the future climate be like? Scientists around the world are studying climate change, putting together models of the Earth’s system and large observational datasets in the hopes of understanding – and predicting over the next 100 years – the planet’s climate. But which models are the most plausible and reflect the future of the planet’s climate the best?

 

In an attempt to answer that question and evaluate the plausibility of a given model, EPFL scientists have developed a rating system and classified climate model outputs generated by the global climate community and included in the recent IPCC report. The EPFL climate scientists find that roughly a third of the models are not doing a good job at reproducing existing sea surface temperature data, a third of them are robust and are not particularly sensitive to carbon emissions, and the other third are also robust but predict a particularly hot future for the planet due to high sensitivity to carbon emissions. The results are published in Nature Communications.

 

“We show that the carbon sensitive models, the ones that predict much stronger heating than the most probable IPCC estimate, are plausible and should be taken seriously,” says Athanasios (Thanos) Nenes, EPFL professor of the Laboratory of Atmospheric Processes and their Impacts, affiliate researcher at the Foundation for Research and Technology Hellas, and author of the study together with graduate student Lucile Ricard.

 

“In other words, the current measures to reduce carbon emissions, which are based on lower carbon sensitivity estimates, may not be enough to curb a catastrophically hot future,” says Ricard.

 

Evaluating the plausibility of a climate model: big data analysis

 

Since the mid 1800’s, the scientific community has been systematically observing the planet, measuring meteorological variables such as temperature, humidity, atmospheric pressure, wind, precipitation, ocean and ice status on Earth. Especially over the last few decades, with observational networks and the deployment of satellites, the amount of observational data is vast, and using this information to predict every aspect of the climate’s future is a daunting task.

 

To evaluate a given climate model, the EPFL researchers developed a tool called “netCS” to cluster climate model outputs using machine learning, synthesizing their behavior by region and comparing the outcome with existing data. With the help of netCS, scientists can determine which climate simulations best reproduces observations in the most meaningful way – and rank them accordingly.

 

“Our approach is an effective way to quickly evaluate a given climate model thanks to netCS’s ability to sift through terabytes of data in one afternoon,” notes Ricard. “Our model rating is a novel type of model evaluation, and highly complements those obtained from historical records, paleoclimate records and process understanding outlined in the 2021 IPCC AR6 assessment report.”

 

Nenes, who is invited to participate in the IPCC AR7 scoping meeting to be held in Malaysia, is of Greek origin. He recalls giving a piano concert in Athens in the middle of the summer almost thirty years ago: “The temperatures back then peaked between 33 and 36 degrees Celsius and were considered to be amongst the highest temperatures of the year. I’ll never forget how difficult it was to play the piano in that heat. Greece is now often plagued with summer temperatures above 40 degrees. Forest fires are commonplace, even invading cities, recently burning neighborhoods that I used to live in. And it will only get worse. The planet is literally burning. Temperatures worldwide are consecutively, year after year, breaking records with all of its consequences.”

 

“Sometimes I feel that climate scientists are a bit like Cassandra of Greek mythology,” concludes Nenes. “She was granted the power of prophecy, but was cursed so that no one would listen to her. But this inertia or lack of action should motivate not discourage us. We have to collectively wake up and really address climate change, because it may be accelerating much more than what we thought”.

 

Other authors included in the study are Fabrizio Falasca from the Courant Institute of Mathematical Sciences at New York University, and Jacob Runge from the Technical University of Berlin. This research was supported by the European Union’s Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant agreement No. 860100 (iMIRACLI), by the FORCeS project under the European Union’s Horizon 2020 research program with grant agreement No. 821205, and by the CleanCloud project under the Horizon Europe research program with grant agreement No. 101137639.

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Journal

Nature Communications

DOI

10.1038/s41467-024-50813-z 

 

Lab data confirm potential of geothermal’s holy grail: superdeep, superhot rock as important renewable energy source

Ability to form fractures spells better economics for resource

Science Communications

 

image: 

Data reported in Nature Communications confirm the potential of geothermal’s holy grail: superdeep, superhot rock as an important renewable energy source.

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Credit: Quaise Energy

HOUSTON, Texas--New laboratory data confirm the potential for geothermal’s holy grail: tapping into the superhot, superdeep rock miles below our feet, which could create a clean, renewable energy source capable of replacing a significant amount of the fossil fuels associated with global warming. The data, reported in the journal Nature Communications, are among the first to show that such rock can form fractures that connect and make it more permeable. Until now, geologists were divided as to whether this was possible.

 

Such fractures are important because water passing through them can become supercritical, a steam-like phase that most people aren’t familiar with. (Familiar phases are liquid water, ice, and the vapor that makes clouds.) Supercritical water, in turn, “can penetrate fractures faster and more easily and can carry far more energy per well to the surface—roughly five to ten times the energy produced by today’s commercial geothermal wells”, according to “Superhot Rock Geothermal, A Vision for Zero-Carbon Energy ‘Everywhere,’” a 2021 report by the Clean Air Task Force.

 

The data also show that rock that fractures at superhot conditions can be ten times more permeable than rock that fractures at conditions closer to the Earth’s surface, and can also deform more readily. Those factors could make this geothermal resource “much more economic,” says Geoffrey Garrison, Vice President of Operations for Quaise Energy, one of the funders for the work. Quaise is working on a novel drilling technique for accessing superdeep, superhot rock.

 

A Geological Debate

 

Until now, geologists had been divided as to whether this superdeep, superhot resource can be tapped. Rock under such high pressures and temperatures—more than 375oC, or 707 oF—is ductile, or gooey, as opposed to a smashable stone from your backyard. As a result, some have argued that fractures can’t be created. And if they can, will they stay open?

 

The current work, led by a team at the Ecole Polytechnique Fédéral de Lausanne (EPFL), confirms that fractures can indeed form in superhot, superdeep rock located near the brittle-to-ductile transition in the crust. The latter is where hard, brittle rock begins to transition into a material that’s ductile, or more pliable.

 

“There are also lots of other data coming out of this work that will inform our approach to tapping the resource,” Garrison says. For example, “how strong is the rock? How far do the fractures go? How many fractures can we create?”

 

“All of this will help us derisk the drilling involved, which is very expensive. You don’t get a lot of chances. You don’t get to drill a hole then, like hanging a picture, move it over if you’ve missed the best location.”

 

“Exciting Finding”

 

Peter Massie is director of the Geothermal Energy Office at the Cascade Institute, which recently released a report with the Clean Air Task Force about drilling for superhot geothermal energy. Massie, who was not involved in the Nature Communications work, made the following comment about it on X: 

 

“Exciting finding: extreme heat & pressure can help create better enhanced geothermal systems [EGS]. At very high temps, rocks become ductile (plasticky), which was expected to impede EGS. This supports [the] prospect of ultradeep, 'supercritical' geothermal with major boost in output.”

 

The research was led by Associate Professor Marie Violay, head of the Laboratory of Experimental Rock Mechanics at EPFL. Says Violay:

 

“This work is exciting because it presents the first permeability measurements conducted during deformation at pressure and temperature conditions characteristic of deep supercritical geothermal reservoirs near the brittle-to-ductile transition in the crust.

 

“We have shown that the brittle-to-ductile transition is not a cutoff for fluid circulation in the crust, which is promising for the exploitation of deep geothermal reservoirs. There are very few in situ data available, and these are among the first experimental results that shed light on such extreme conditions.”

 

Violay’s coauthors of the Nature Communications paper are first author Gabriel G. Meyer and Ghassan Shahin, both of EPFL, and Benoit Cordonnier of the European Synchrotron Radiation Facility.

 

What’s Happening?

 

The consistency of superhot, superdeep rock is similar to that of Silly Putty. “If you pull it slowly, it stretches out and becomes elastic. But if you pull a chunk of Silly Putty really quickly, it snaps. And that is brittle behavior,” says Garrison.

 

In other words, he continues, “if you stress the rock slowly enough under these extreme conditions, it may stretch and not fracture. This work shows that rock will shatter under these conditions, but it needs to be stressed quickly to do so.”

 

The research confirms theoretical work reported earlier this year in Geothermal Energy showing that the cracks that form create a dense “cloud of permeability” throughout the affected rock. This is in contrast to the much larger and fewer macroscopic fractures induced by the engineered geothermal systems (EGS) in use today, which operate closer to the surface and at much lower temperatures.

 

As a result, the simulations involved in the Geothermal Energy work predict that a superhot system can deliver five to ten times more power than typically produced today from EGS, and do so for up to two decades.

 

Unique Experimental Machine

 

Garrison notes that there are very few facilities in the world capable of making the measurements conducted at EPFL.

 

Says Violay, “The best part [of this research] was the development of a unique experimental machine capable of reproducing the pressure, temperature, and deformation conditions of deep supercritical reservoirs near the brittle-to-ductile transition. Additionally, we were able to combine these experimental results with in situ X-ray images obtained the ESRF (European Synchrotron Radiation Facility), offering a comprehensive view of the processes involved.”

 

In addition to Quaise Energy, this work was funded by the European Research Council, the Swiss National Science Foundation, The European Union’s Horizon 2020 research and innovation program, the Swiss Federal Office of Energy, and Alta Rock Energy.

 

For more information, see the following stories:

 

Scientists explore the complexity of rocks within the Earth's crust

By Rebecca Mosimann

EPFL (Ecole Polytechnique Fédéral de Lausanne)

October 8, 2024

 

New results show potential for boost in geothermal energy

By Montserrat Capellas Espuny

ESRF (European Synchrotron Radiation Facility)

September 9, 2024

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Journal

Nature Communications

DOI

10.1038/s41467-024-52092-0 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Permeability partitioning through the brittle-to-ductile transition and its implications for supercritical geothermal reservoirs

SPACE

Galaxies are much much bigger than we thought

The inside story of a galaxy’s long reach into space

Peer-Reviewed Publication

ARC Centre of Excellence for All Sky Astrophysics in 3D (ASTRO 3D)

 

image: 

Dr Nikole (Nikki) Nielsen visiting Keck in Hawaii

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Credit: Provided

If this galaxy is typical, then the study, published today in Nature Astronomy, indicates that our galaxy is already interacting with its closest neighbour, Andromeda. 

Where does a galaxy end and deep space begin? It seems like a simple question until you look more closely at the gas that surrounds galaxies, known as the circumgalactic medium. 

The halo of gas surrounding the stellar disc accounts for about 70% of the mass of the galaxy – excluding dark matter – but until now has remained something of a mystery. In the past we have only been able to observe the gas by measuring the light from a background object, such as a quasar, that is absorbed by the gas.

That limits the picture of the cloud to a pencil-like beam.

A new study, however, has observed the circumgalactic medium of a star-bursting galaxy 270 million light years away, using new deep imaging techniques that were able to detect the cloud of gas glowing outside of the galaxy 100,000 light years into space, as far as they were able to look.

To envisage the vastness of that cloud of gas, consider that the galaxy’s starlight – what we would typically view as the disc – extends just 7,800 light years from its centre.

The current study observed the physical connection of hydrogen and oxygen from the centre of the galaxy far into space and showed that the physical conditions of the gas changed.

“We found it everywhere we looked, which was really exciting and kind of surprising,” says Associate Professor Nikole M. Nielsen, lead author of the paper, and a researcher with Swinburne University, and ASTRO 3D and an Assistant Professor at the University of Oklahoma.

Other authors of the paper came from Swinburne, the University of Texas at Austin, the California Institute of Technology, Pasadena, the University of California, San Diego, and Durham University. 

“We’re now seeing where the galaxy's influence stops, the transition where it becomes part of more of what’s surrounding the galaxy, and, eventually, where it joins the wider cosmic web and other galaxies. These are all usually fuzzy boundaries,” says Dr Nielsen.

“But in this case, we seem to have found a fairly clear boundary in this galaxy between its interstellar medium and its circumgalactic medium.”

The study observed stars ionizing gas with their photons within the galaxy. 

“In the CGM, the gas is being heated by something other than typical conditions inside galaxies, this likely includes heating from the diffuse emissions from the collective galaxies in the Universe and possibly some contribution is due to shocks,” says Dr Nielsen.

“It's this interesting change that is important and provides some answers to the question of where a galaxy ends,” she says.

The discovery has been made possible thanks to the Keck Cosmic Web Imager (KCWI) on the 10-meter Keck telescope in Hawaii, which contains an integral field spectrograph and is one of the most sensitive instruments of its kind in operation. 

“These one-of-a-kind observations require the very dark sky that is only available at the Keck Observatory on Mauna Kea,” said one of the paper’s authors, Swinburne’s Associate Professor Deanne Fisher.

ASTRO 3D scientists gained access to KCWI through Swinburne University.

“Swinburne’s Partnership with the W. M. Keck Observatory has allowed our team to really push the boundaries of what is possible,” says another author, Associate Professor Glenn Kacprzak. “KCWI has really changed the game on how we can now measure and quantify the diffuse gas around galaxies.”

Thanks to the instrument, rather than making a single observation providing a single spectrum of the gas in the galaxy, scientists can now obtain thousands of spectra simultaneously with one image from KCWI. 

“It is the very first time that we have been able to take a photograph of this halo of matter around a galaxy,” says Professor Emma Ryan-Weber, the Director of ASTRO 3D.

The study adds another piece to the puzzle that is one of the big questions in astronomy and galaxy evolution – how do galaxies evolve? How do they get their gas? How do they process that gas? Where does that gas go.

“The circumgalactic medium plays a huge role in that cycling of that gas,” says Dr Nielsen. “So, being able to understand what the CGM looks like around galaxies of different types – ones that are star-forming, those that are no longer star-forming, and those that are transitioning between the two –we can observe differences in this gas, which might drive the differences within the galaxies themselves, and changes in this reservoir may actually be driving the changes in the galaxy itself.”

The study speaks directly to the ASTRO 3D’s mission. “It helps us understand how galaxies build mass over time,” says Professor Ryan-Weber.

The findings could also hold implications for how different galaxies interact and how they might impact each other.

“It’s highly likely that the CGMs of our own Milky Way and Andromeda are already overlapping and interacting,” says Dr Nielsen.

Visualisation of the gas shroud of starburst galaxy IRAS 08339+6517

Credit

Cristy Roberts ANU/ASTRO 3D

Lead author, Nikki Nielsen with colleagues Glenn Kacprzak and Stephanie Pointon in front of the Keck mirror

Credit

Provided

Journal

Nature Astronomy

DOI

10.1038/s41550-024-02365-x 

Article Title

An emission map of the disk–circumgalactic medium transition in starburst IRAS 08339+6517

Article Publication Date

6-Sep-2024

NASA’s Hubble, MAVEN help solve the mystery of Mars’ escaping water

NASA/Goddard Space Flight Center

 

image: 

These are far-ultraviolet Hubble images of Mars near its farthest point from the Sun, called aphelion, on December 31, 2017 (top), and near its closest approach to the Sun, called perihelion, on December 19, 2016 (bottom). The atmosphere is clearly brighter and more extended when Mars is close to the Sun. Reflected sunlight from Mars at these wavelengths shows scattering by atmospheric molecules and haze, while the polar ice caps and some surface features are also visible. Hubble and MAVEN showed that Martian atmospheric conditions change very quickly. When Mars is close to the Sun, water molecules rise very rapidly through the atmosphere, breaking apart and releasing atoms at high altitudes.

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Credit: NASA, ESA, STScI, John T. Clarke (Boston University); Processing: Joseph DePasquale (STScI)

Mars was once a very wet planet as is evident in its surface geological features. Scientists know that over the last 3 billion years, at least some water went deep underground, but what happened to the rest? Now, NASA's Hubble Space Telescope and MAVEN (Mars Atmosphere and Volatile Evolution) missions are helping unlock that mystery.

"There are only two places water can go. It can freeze into the ground, or the water molecule can break into atoms, and the atoms can escape from the top of the atmosphere into space," explained study leader John Clarke of the Center for Space Physics at Boston University in Massachusetts. "To understand how much water there was and what happened to it, we need to understand how the atoms escape into space."

Clarke and his team combined data from Hubble and MAVEN to measure the number and current escape rate of the hydrogen atoms escaping into space. This information allowed them to extrapolate the escape rate backwards through time to understand the history of water on the Red Planet.

Escaping Hydrogen and "Heavy Hydrogen"

Water molecules in the Martian atmosphere are broken apart by sunlight into hydrogen and oxygen atoms. Specifically, the team measured hydrogen and deuterium, which is a hydrogen atom with a neutron in its nucleus. This neutron gives deuterium twice the mass of hydrogen. Because its mass is higher, deuterium escapes into space much more slowly than regular hydrogen.

Over time, as more hydrogen was lost than deuterium, the ratio of deuterium to hydrogen built up in the atmosphere. Measuring the ratio today gives scientists a clue to how much water was present during the warm, wet period on Mars. By studying how these atoms currently escape, they can understand the processes that determined the escape rates over the last four billion years and thereby extrapolate back in time.

Although most of the study's data comes from the MAVEN spacecraft, MAVEN is not sensitive enough to see the deuterium emission at all times of the Martian year. Unlike the Earth, Mars swings far from the Sun in its elliptical orbit during the long Martian winter, and the deuterium emissions become faint. Clarke and his team needed the Hubble data to "fill in the blanks" and complete an annual cycle for three Martian years (each of which is 687 Earth days). Hubble also provided additional data going back to 1991 – prior to MAVEN's arrival at Mars in 2014.

The combination of data between these missions provided the first holistic view of hydrogen atoms escaping Mars into space.

A Dynamic and Turbulent Martian Atmosphere

"In recent years scientists have found that Mars has an annual cycle that is much more dynamic than people expected 10 or 15 years ago," explained Clarke. "The whole atmosphere is very turbulent, heating up and cooling down on short timescales, even down to hours. The atmosphere expands and contracts as the brightness of the Sun at Mars varies by 40 percent over the course of a Martian year."

The team discovered that the escape rates of hydrogen and deuterium change rapidly when Mars is close to the Sun. In the classical picture that scientists previously had, these atoms were thought to slowly diffuse upward through the atmosphere to a height where they could escape.

But that picture no longer accurately reflects the whole story, because now scientists know that atmospheric conditions change very quickly. When Mars is close to the Sun, the water molecules, which are the source of the hydrogen and deuterium, rise through the atmosphere very rapidly releasing atoms at high altitudes.

The second finding is that the changes in hydrogen and deuterium are so rapid that the atomic escape needs added energy to explain them. At the temperature of the upper atmosphere only a small fraction of the atoms have enough speed to escape the gravity of Mars. Faster (super-thermal) atoms are produced when something gives the atom a kick of extra energy. These events include collisions from solar wind protons entering the atmosphere or sunlight that drives chemical reactions in the upper atmosphere.

Serving as a Proxy

Studying the history of water on Mars is fundamental not only to understanding planets in our own solar system but also the evolution of Earth-size planets around other stars. Astronomers are finding more and more of these planets, but they’re difficult to study in detail. Mars, Earth and Venus all sit in or near our solar system's habitable zone, the region around a star where liquid water could pool on a rocky planet; yet all three planets have dramatically different present-day conditions. Along with its sister planets, Mars can help scientists grasp the nature of far-flung worlds across our galaxy.

These results appear in the July 26 edition of Science Advances, published by the American Association for the Advancement of Science.

About the Missions

The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, Colorado, also supports mission operations at Goddard. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.

MAVEN’s principal investigator is based at the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder. LASP is also responsible for managing science operations and public outreach and communications. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the MAVEN mission. Lockheed Martin Space built the spacecraft and is responsible for MAVEN mission operations at Goddard. NASA’s Jet Propulsion Laboratory in Southern California provides navigation and Deep Space Network support. The MAVEN team is preparing to celebrate the spacecraft’s 10th year at Mars in September 2024.

@NASAHubble

@NASAHubble

@NASAHubble

Journal

Science Advances

DOI

10.1126/sciadv.adm7499 

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

Martian atmospheric hydrogen and deuterium: Seasonal changes and paradigm for escape to space

Gravitational waves unveil previously unseen properties of neutron stars

University of Illinois at Urbana-Champaign, News Bureau

 

image: 

Illinois researchers Rohit Chandramouli, left, professor Nicolas Yunes and Abhishek Hegade used computer simulations, analytical models and sophisticated data analyses to verify that forces within binary neutron star systems are detectable via gravitational waves.

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Credit: Photo by Fred Zwicky

CHAMPAIGN, Ill. — A better understanding of the inner workings of neutron stars will lead to a greater knowledge of the dynamics that underpin the workings of the universe and also could help drive future technology, said the University of Illinois Urbana-Champaign physics professor Nicolas Yunes. A new study led by Yunes details how new insights into how dissipative tidal forces within double — or binary — neutron star systems will inform our understanding of the universe.

“Neutron stars are the collapsed cores of stars and densest stable material objects in the universe, much denser and colder than conditions that particle colliders can even create,” said Yunes, who also is the founding director of the Illinois Center for Advanced Studies of the Universe. “The mere existence of neutron stars tells us that there are unseen properties related to astrophysics, gravitational physics and nuclear physics that play a critical role in the inner workings of our universe.”

However, many of these previously unseen properties became observable with the discovery of gravitational waves.

“The properties of neutron stars imprint onto the gravitational waves they emit. These waves then travel millions of light-years through space to detectors on Earth, like the advanced European Laser Interferometer Gravitational-Wave Observatory and the Virgo Collaboration,” Yunes said. “By detecting and analyzing the waves, we can infer the properties of neutron stars and learn about their internal composition and the physics at play in their extreme environments.”

As a gravitational physicist, Yunes was interested in determining how gravitational waves encode information about the tidal forces that distort the shape of neutron stars and affect their orbital motion. This information also could tell physicists more about the dynamic material properties of the stars, such as internal friction or viscosity, “which might give us insight into out-of-equilibrium physical processes that result in the net transfer of energy into or out of a system,” Yunes said.

Using data from the gravitational wave event identified as GW170817, Yunes, along with Illinois researchers Justin Ripley, Abhishek Hegade and Rohit Chandramouli, used computer simulations, analytical models and sophisticated data analysis algorithms to verify that out-of-equilibrium tidal forces within binary neutron star systems are detectable via gravitational waves. The GW170817 event was not loud enough to yield a direct measurement of viscosity, but Yunes’ team was able to place the first observational constraints on how large viscosity can be inside neutron stars.

The study findings are published in the journal Nature Astronomy.

“This is an important advance, particularly for ICASU and the U. of I.,” Yunes said. “In the '70s, '80s and '90s, Illinois pioneered many of the leading theories behind nuclear physics, particularly those connected to neutron stars. This legacy can continue with access to data from the advanced LIGO and Virgo detectors, the collaborations made possible through ICASU and the decades of nuclear physics expertise already in place here.”

The University of Illinois Graduate College Dissertation Completion Fellowship and the National Science Foundation supported this study.

 

Editor’s note:                 

To reach Nicolas Yunes, email nyunes@illinois.edu.

The paper “A constraint on the dissipative tidal deformability of neutron stars” is available online. DOI: 10.1038/s41550-024-02323-7.

Physics is part of The Grainger College of Engineering at the University of Illinois Urbana-Champaign.  

 

 

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Journal

Nature Astronomy

DOI

10.1038/s41550-024-02323-7 

Method of Research

Computational simulation/modeling

Subject of Research

Not applicable

Article Title

A constraint on the dissipative tidal deformability of neutron stars

Plasmonic modulators could enable high-capacity space communication

High-speed free-space data transmission could improve connectivity for space missions

Optica

 

image: 

Fig. 1 Experimental setup of the FSO outdoor experiments. Tunable laser source (TLS), driving amplifier (DA), arbitrary waveform generator (AWG), transmitter digital signal processing (Tx-DSP), erbium-doped fiber amplifier (EDFA), bandpass filter (BPF), optical spectrum analyzer (OSA), polarization division multiplexing emulator (PDM), high power optical amplifier (HPOA), real time controller (RTC), deformable mirror (DFM), wafefront sensor (WFS), optical power meter (OPM), local oscillator (LO), balanced photodetector (BPD), digital storage oscilloscope (DSO), receiver digital signal processing (Rx-DSP)

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Credit: Laurenz Kulmer, ETH Zurich

Researchers have achieved data rates as high as 424Gbit/s across a 53-km turbulent free-space optical link using plasmonic modulators— devices that uses special light waves called surface plasmon polaritons to control and change optical signals. The new research lays the groundwork for high-speed optical communication links that transmit data over open air or space.

Free-space-optical communication networks could aid space exploration because they can provide high-speed, high-capacity data transmission with lower latency and less interference than traditional radio frequency communication systems. This could lead to more efficient data transfer, better connectivity and enhanced capabilities for space missions.

Laurenz Kulmer from the Leuthold group of ETH Zurich will present this research at Frontiers in Optics + Laser Science (FiO LS), which will be held 23 – 26 September 2024 at the Colorado Convention Center in Denver.

 “High-speed free-space transmission is an option to connect the world, or it may serve as a backup if underwater cables break,” said Kulmer. “Nevertheless, it is also a step towards a new cheap high-speed internet that may connect all locations across the world. This way it may contribute towards a stable, high-speed internet for millions of people who are currently unconnected.”

Plasmonic modulators are ideal for space communication links because they are compact while also operating at high speeds over a wide temperature range with low energy consumption.

In free-space optical outdoor experiments, the researchers achieved information rates of up to 424 Gbit/s below a 25% SD FEC threshold — the point at which a system can still fix errors in transmitted data despite interference or noise. Experiments using a plasmonic IQ modulator in a standard fiber system achieved an even higher throughput of up to 774 Gbit/s/pol while staying below a 25% SD FEC threshold.

Based on these results, the researchers say that combining plasmonic modulators with coherent free-space optical communication could help increase overall throughput, with speeds potentially reaching 1.4 Tbit/s. The findings also show that it is favorable to operate free-space optical links at the highest speeds, rather than using higher order modulation formats and low speeds. With additional improvements in device design and photonic integration, the researchers say it should be feasible to reach polarization multiplexing data rates above 1 Tbit/s for each polarization channel.

“In a next step we are going to test the long-term reliability of our devices,” said Kulmer. “High-speed performance has been shown, but we have to make sure they can operate for years to come in the harshest of environments, space.”

About Frontiers in Optics + Laser Science

Frontiers in Optics, the annual meeting for Optica is presented with Laser Science, the annual meeting of the American Physical Society, Division of Laser Science. The two meetings unite communities from both societies for comprehensive and current research in a diverse collection of optics and photonics topics and across the disciplines of physics, biology and chemistry. The 2024 FiO LS Conference will feature hundreds of live contributed and invited talks. More information at https://www.frontiersinoptics.com.

About Optica

Optica, Advancing Optics and Photonics Worldwide, is the society dedicated to promoting the generation, application, archiving and dissemination of knowledge in the field. Founded in 1916, it is the leading organization for scientists, engineers, business professionals, students and others interested in the science of light. Optica's renowned publications, meetings, online resources and in-person activities fuel discoveries, shape real-life applications and accelerate scientific, technical and educational achievement. Discover more at: Optica.org

Astrophysics: AI shines a new light on exoplanets

Ludwig-Maximilians-Universität München

A team led by LMU researchers models the atmospheres of distant planets using neural networks

Researchers from LMU, the ORIGINS Excellence Cluster, the Max Planck Institute for Extraterrestrial Physics (MPE), and the ORIGINS Data Science Lab (ODSL) have made an important breakthrough in the analysis of exoplanet atmospheres. Using physics-informed neural networks (PINNs), they have managed to model the complex light scattering in the atmospheres of exoplanets with greater precision than has previously been possible. This method opens up new opportunities for the analysis of exoplanet atmospheres, especially with regard to the influence of clouds, and could significantly improve our understanding of these distant worlds.

When distant exoplanets pass in front of their star, they block a small portion of the starlight, while an even smaller portion penetrates the planetary atmosphere. This interaction leads to variations in the light spectrum, which mirror the properties of the atmosphere such as chemical composition, temperature, and cloud cover. To be able to analyze these measured spectra, however, scientists require models that are capable of calculating millions of synthetic spectra in a short time. Only by subsequently comparing the calculated spectra with the measured ones do we obtain information about the atmospheric composition of the observed exoplanets. And what is more, the highly detailed new observations coming from the James Webb Space Telescope (JWST) necessitate equally detailed and complex atmospheric models.

Rapid solving of complex equations thanks to AI

A key aspect of exoplanet research is the light scattering in the atmosphere, particularly the scattering off clouds. Previous models were unable to satisfactorily capture this scattering, which led to inaccuracies in the spectral analysis. Physics-informed neural networks offer a decisive advantage here, as they are capable of efficiently solving complex equations. In the just-published study, the researchers trained two such networks. The first model, which was developed without taking light scattering into account, demonstrated impressive accuracy with relative errors of mostly under one percent. Meanwhile, the second model incorporated approximations of so-called Rayleigh scattering – the same effect that makes the sky seem blue on Earth. Although these approximations require further improvement, the neural network was able to solve the complex equation, which represents an important advance.

Interdisciplinary collaboration

These new findings were possible thanks to a unique interdisciplinary collaboration between physicists from LMU Munich, the ORIGINS Excellence Cluster, the Max Planck Institute for Extraterrestrial Physics (MPE) and the ORIGINS Data Science Lab (ODSL), which is specialized in the development of new AI-based methods in physics. “This synergy not only advances exoplanet research, but also opens up new horizons for the development of AI-based methods in physics,” explains lead author of the study David Dahlbüdding from LMU. “We want to further expand our interdisciplinary collaboration in the future to simulate the scattering of light off clouds with greater precision and thus make full use of the potential of neural networks.”

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Journal

Monthly Notices of the Royal Astronomical Society

DOI

10.1093/mnras/stae1872 

Article Title

Approximating Rayleigh scattering in exoplanetary atmospheres using physics-informed neural networks

Massive merger: study reveals evidence for origin of supermassive black hole at galaxy’s center

UNLV astrophysicists analyze data from Event Horizon Telescope’s groundbreaking imaging of Sagittarius A* and suggest it formed by merger of two black holes roughly 9 billion years ago

University of Nevada, Las Vegas

LAS VEGAS -- September 6, 2024 -- The origins of aptly named supermassive black holes – which can weigh in at more than a million times the mass of the sun and reside in the center of most galaxies – remain one of the great mysteries of the cosmos. 

Now, researchers from the Nevada Center for Astrophysics at UNLV (NCfA) have discovered compelling evidence suggesting that the supermassive black hole at the center of our Milky Way galaxy, known as Sagittarius A* (Sgr A*), is likely the result of a past cosmic merger. 

The study, published Sept. 6 in the journal Nature Astronomy, builds on recent observations from the Event Horizon Telescope (EHT), which captured the first direct image of Sgr A* in 2022. The EHT, the result of a global research collaboration, syncs data from eight existing radio observatories worldwide to create a massive, Earth-sized virtual telescope. 

UNLV astrophysicists Yihan Wang and Bing Zhang utilized the data from the EHT observation of Sgr A* to look for evidence on how it may have formed. Supermassive black holes are thought to grow either by the accretion of matter over time, or by the merger of two existing black holes. 

The UNLV team investigated various growth models to understand the peculiar rapid spin and misalignment of Sgr A* relative to the Milky Way’s angular momentum. The team demonstrated that these unusual characteristics are best explained by a major merger event involving Sgr A* and another supermassive black hole, likely from a satellite galaxy.

“This discovery paves the way for our understanding of how supermassive black holes grow and evolve,” said Wang, the lead author of the study and an NCfA postdoctoral fellow at UNLV. “The misaligned high spin of Sgr A* indicates that it may have merged with another black hole, dramatically altering its amplitude and orientation of spin.”

Using sophisticated simulations, the researchers modeled the impact of a merger, considering various scenarios that align with the observed spin properties of Sgr A*. Their results indicate that a 4:1 mass ratio merger with a highly inclined orbital configuration could reproduce the spin properties observed by the EHT. 

“This merger likely occurred around 9 billion years ago, following the Milky Way’s merger with the Gaia-Enceladus galaxy,” said Zhang, a distinguished professor of physics and astronomy at UNLV and the founding director of the NCfA. “This event not only provides evidence of the hierarchical black hole merger theory but also provides insights into the dynamical history of our galaxy.” 

Sgr A* sits at the center of the galaxy more than 27,000 light years away from Earth, and sophisticated tools like the EHT provide direct imaging that helps scientists put predictive theories to the test. 

Researchers say that the findings from the study will have significant implications for future observations with upcoming space-borne gravitational wave detectors, such as the Laser Interferometer Space Antenna (LISA), which is planned to launch in 2035 and is expected to detect similar supermassive black hole mergers across the universe.

Study Details
“Evidence of a Past Merger of the Galactic Centre Black Hole” was published Sept. 6 in the journal Nature Astronomy. Study authors are Yihan Wang and Bing Zhang with the Nevada Center for Astrophysics and the Department of Physics and Astronomy at UNLV.

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Journal

Nature Astronomy

DOI

10.1038/s41550-024-02358-w 

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

Evidence of a past merger of the Galactic Centre black hole

Article Publication Date

6-Sep-2024

AI helps distinguish dark matter from cosmic noise

Ecole Polytechnique Fédérale de Lausanne

Dark matter is the invisible force holding the universe together – or so we think. It makes up around 85% of all matter and around 27% of the universe’s contents, but since we can’t see it directly, we have to study its gravitational effects on galaxies and other cosmic structures. Despite decades of research, the true nature of dark matter remains one of science’s most elusive questions.

According to a leading theory, dark matter might be a type of particle that barely interacts with anything else, except through gravity. But some scientists believe these particles could occasionally interact with each other, a phenomenon known as self-interaction. Detecting such interactions would offer crucial clues about dark matter’s properties.

However, distinguishing the subtle signs of dark matter self-interactions from other cosmic effects, like those caused by active galactic nuclei (AGN) – the supermassive black holes at the centers of galaxies – has been a major challenge. AGN feedback can push matter around in ways that are similar to the effects of dark matter, making it difficult to tell the two apart.

In a significant step forward, astronomer David Harvey at EPFL’s  Laboratory of Astrophysics has developed a deep-learning algorithm that can untangle these complex signals. Their AI-based method is designed to differentiate between the effects of dark matter self-interactions and those of AGN feedback by analyzing images of galaxy clusters – vast collections of galaxies bound together by gravity. The innovation promises to greatly enhance the precision of dark matter studies.

Harvey trained a Convolutional Neural Network (CNN) – a type of AI that is particularly good at recognizing patterns in images – with images from the BAHAMAS-SIDM project, which models galaxy clusters under different dark matter and AGN feedback scenarios. By being fed thousands of simulated galaxy cluster images, the CNN learned to distinguish between the signals caused by dark matter self-interactions and those caused by AGN feedback.

Among the various CNN architectures tested, the most complex - dubbed “Inception” – proved to also be the most accurate. The AI was trained on two primary dark matter scenarios, featuring different levels of self-interaction, and validated on additional models, including a more complex, velocity-dependent dark matter model.

Inception achieved an impressive accuracy of 80% under ideal conditions, effectively identifying whether galaxy clusters were influenced by self-interacting dark matter or AGN feedback. It maintained is high performance even when the researchers introduced realistic observational noise that mimics the kind of data we expect from future telescopes like Euclid.

What this means is that Inception – and the AI approach more generally – could prove incredibly useful for analyzing the massive amounts of data we collect from space. Moreover, the AI’s ability to handle unseen data indicates that it’s adaptable and reliable, making it a promising tool for future dark matter research.

AI-based approaches like Inception could significantly impact our understanding of what dark matter actually is. As new telescopes gather unprecedented amounts of data, this method will help scientists sift through it quickly and accurately, potentially revealing the true nature of dark matter.

Reference

D. Harvey. A deep-learning algorithm to disentangle self-interacting dark matter and AGN feedback models. Nature Astronomy 06 September 2024. DOI: 10.1038/s41550-024-02322-8

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Journal

Nature Astronomy

DOI

10.1038/s41550-024-02322-8 

Article Title

A deep-learning algorithm to disentangle self-interacting dark matter and AGN feedback models.

Article Publication Date

6-Sep-2024

Weather in deep space -- Trinity astrophysicist wins European Research Council Starting Grant

Trinity College Dublin

 

image: 

Dr Johanna Vos in Trinity College Dublin.

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Credit: Trinity College Dublin.

Drs Johanna Vos has won a highly prestigious European Research Council (ERC) Starting Grants to pursue research aimed at better understanding weather patterns in extrasolar worlds deep in the galaxy.

Dr Vos’ project: Exometeorology: Probing Extrasolar Atmospheres (Exo-PEA)

Over the past 30 years, astronomers have uncovered thousands of new extrasolar planets, which vary from small, rocky worlds, to giant planets like Jupiter. Additionally, lots of isolated or free-floating worlds have been discovered. We have already learned that the atmospheres of these strange worlds are highly complex, hosting a range of weather processes. 

The launch of the James Webb Space Telescope (JWST) enables a new era in our understanding of extrasolar atmospheres. By providing observations of unprecedented quality, this ground-breaking facility opens a new window into these atmospheres. 

Dr Vos was recently awarded three observing programmes as PI with the JWST that form the basis of her ERC project. By combining new data from these programmes with state of the art computational and data-driven techniques, her team will reveal the dominant atmospheric processes that give rise to weather on giant extrasolar worlds.

Dr Vos, Assistant Professor in Trinity’s School of Physics, said: “I am honoured to have been awarded this ERC Starting Grant and for the opportunity to expand the breadth and scope of research in my group. This funding will allow me to build a team that will make use of ground-breaking data from JWST to provide key insights into the atmospheres of worlds beyond our solar system.”

ERC Starting Grants draw funding from the EU’s Horizon Europe programme to enable excellent scientists, with up to seven years of post-PhD experience, to pursue their most promising ideas. The funds also enable recipients to significantly grow their research teams over the five-year duration of the projects they support.

Researchers discover a space oddity – an exoplanet moving in mysterious ways

Lund University

A research team led by Lund University in Sweden has discovered a small planet that displays peculiar orbital motion. The shimmying planet, located 455 light-years from Earth, shows that planetary systems can be considerably more complex than researchers have previously thought. 

The newly discovered planet TOI-1408c has a mass equivalent to eight Earths and circles very close to a larger planet, the hot gas giant TOI-1408b. After starting to study both planets and their star, TOI-1408, in detail, the researchers felt puzzled. The small planet has a very peculiar orbital motion. The interactions between the two planets and their star can be likened to a rhythmic dance.

“The small planet exhibits very unusual orbital behaviour and shows considerable variations regarding the time when it passes in front of its star, which is something that we don’t see as a rule. The small planet’s existence challenges existing theories on the formation and stability of planetary systems,” says Judith Korth, astrophysicist at Lund University and leader of the study.

The new study, published in The Astrophysical Journal Letters, shows that planetary systems can be considerably more complex than researchers have previously thought. The discovery of a small planet between a star and a gas giant is rare and offers a unique case study for the development of planetary systems. This could help the researchers to understand more about how planets are formed in other solar systems.

“Our results will help researchers to learn more about how planets are formed and how they behave when they are very close to each other, particularly in systems with giant planets,” says Judith Korth.

Exoplanets are planets located in a solar system other than our own. The first confirmed discovery was made in 1995. Since then, over 5,700 exoplanets have been discovered. The researchers’ discovery of the space oddity TOI-1408c was made possible by using NASA’s Transiting Exoplanet Survey Satellite (TESS). Since TESS was launched in 2018, it has observed over 7,000 potential exoplanets.

“I hope that our results can be used in future studies to discover even more planets in other systems, but also to better understand the large range of planetary systems that exist in our galaxy,” concludes Judith Korth.

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Journal

The Astrophysical Journal Letters

DOI

10.3847/2041-8213/ad65fd 

Article Title

TOI-1408: Discovery and Photodynamical Modeling of a Small Inner Companion to a Hot Jupiter Revealed by Transit Timing Variations