Sunday, December 18, 2022

ESPRESSO and CARMENES discover two potentially habitable exo-Earths around a star near the Sun

Peer-Reviewed Publication

INSTITUTO DE ASTROFÍSICA DE CANARIAS (IAC)

Two Earth-mass planets orbiting the star GJ 1002 

IMAGE: ARTIST'S IMPRESSION OF TWO EARTH-MASS PLANETS ORBITING THE STAR GJ 1002 view more 

CREDIT: ALEJANDRO SUÁREZ MASCAREÑO AND INÉS BONET (IAC)

“Nature seems bent on showing us that Earth-like planets are very common. With these two we now know 7 in planetary systems quite near to the Sun” explains Alejandro Suárez Mascareño, an IAC researcher, who is the first author of the study accepted for publication in Astronomy & Astrophysics.

The newly discovered planets orbit the star GJ 1002, which is at a distance of less than 16 light years from the Solar System. Both of them have masses similar to that of the Earth, and they are in the habitability zone of their star. GJ 1002b, the inner of the two, takes little more than 10 days to complete an orbit around the star, while GJ 1002c needs a little over 21 days. “GJ 1002 is a red dwarf star, with barely one eighth the mass of the Sun. It is quite a cool, faint star. This means that its habitability zone is very close to the star” explains Vera María Passegger, a co-author of the article and an IAC researcher.

The proximity of the star to our Solar System implies that the two planets, especially GJ 1002c, are excellent candidates for the characterization of their atmospheres based either on their reflected light, or on their thermal emission. “The future ANDES spectrograph for the ELT telescope at ESO in which the IAC is participating, could study the presence of oxygen in the atmosphere of GJ 1002c” notes Jonay I. González Hernández, an IAC researcher who is a co-author of the article. In addition, both planets satisfy the characteristics needed for them to be objectives for the future LIFE mission, which is presently in a study phase.

The discovery was made during a collaboration between the consortia of the two instruments ESPRESSO and CARMENES. GJ 1002 was observed by CARMENES between 2017 and 2019, and by ESPRESSO between 2019 and 2021. “Because of its low temperature the visible light from GJ 1002 is too faint to measure its variations in velocity with the majority of spectrographs” says says Ignasi Ribas, researcher at the Institute of Space Sciences (ICE-CSIC) and director of the Institut d'Estudis Espacials de Catalunya (IEEC). CARMENES has a sensitivity over a wide range of near infrared wavelengths which is superior to those of other spectrographs aimed at detecting variations in the velocities of stars, and this allowed it to study GJ 1002, from the 3.5m telescope at Calar Alto observatory.

The combination of ESPRESSO, and the light gathering power of the VLT 8m telescopes at ESO allowed measurements to be made with an accuracy of only 30 cm/sec, not attainable with any other instrument in the world. “Either of the two groups would have had many difficulties if they had tackled this work independently. Jointly we have been able to get much further than we would have done acting independently” states Suárez Mascareño.



Webb Space Telescope reveals previously shrouded newborn stars

Webb’s infrared camera peers through dust clouds, enabling discovery

Peer-Reviewed Publication

RICE UNIVERSITY

JWST infrared image of Cosmic Cliffs 

IMAGE: ASTRONOMERS FROM RICE UNIVERSITY AND OTHER ORGANIZATIONS DUG DEEP INTO THE DATA FROM THIS NEAR-INFRARED IMAGE, ONE OF THE FIRST TAKEN BY NASA’S JAMES WEBB SPACE TELESCOPE. THE IMAGE SHOWS A STAR-FORMING REGION IN THE CONSTELLATION CARINA KNOWN AS THE COSMIC CLIFFS. MANY NEWBORN STARS IN SUCH REGIONS ARE SHROUDED IN THICK CLOUDS OF DUST. WEBB’S INFRARED CAMERA PENETRATED THE DUST, ALLOWING ASTRONOMERS TO DISCOVER TELLTALE SIGNS OF TWO DOZEN INFANT STARS THAT HADN’T BEEN PREVIOUSLY DETECTED. view more 

CREDIT: IMAGE COURTESY OF NASA, ESA, CSA AND STSCI

HOUSTON – (Dec. 16, 2022) – Rice University astronomer Megan Reiter and colleagues took a “deep dive” into one of the first images from NASA’s James Webb Space Telescope and were rewarded with the discovery of telltale signs from two dozen previously unseen young stars about 7,500 light years from Earth.

The published research in the December issue of the Monthly Notices of the Royal Astronomical Society offers a glimpse of what astronomers will find with Webb’s near-infrared camera. The instrument is designed to peer through clouds of interstellar dust that have previously blocked astronomers’ view of stellar nurseries, especially those that produce stars similar to Earth’s sun.

Reiter, an assistant professor of physics and astronomy, and co-authors from the California Institute of Technology, the University of Arizona, Queen Mary University in London and the United Kingdom’s Royal Observatory in Edinburgh, Scotland, analyzed a portion of Webb’s first images of the Cosmic Cliffs, a star-forming region in a cluster of stars known as NGC 3324.

“What Webb gives us is a snapshot in time to see just how much star formation is going on in what may be a more typical corner of the universe that we haven’t been able to see before,” said Reiter, who led the study.

Located in the southern constellation Carina, NGC 3324 hosts several well-known regions of star formation that astronomers have studied for decades. Many details from the region have been obscured by dust in images from the Hubble Space Telescope and other observatories. Webb’s infrared camera was built to see through dust in such regions and to detect jets of gas and dust that spew from the poles of very young stars.

Reiter and colleagues focused their attention on a portion of NGC 3324 where only a few young stars had previously been found. By analyzing a specific infrared wavelength, 4.7 microns, they discovered two dozen previously unknown outflows of molecular hydrogen from young stars. The outflows range in size, but many appear to come from protostars that will eventually become low-mass stars like Earth’s sun.

“The findings speak both to how good the telescope is and to how much there is going on in even quiet corners of the universe,” Reiter said.

Within their first 10,000 years, newborn stars gather material from the gas and dust around them. Most young stars eject a fraction of that material back into space via jets that stream out in opposite directions from their poles. Dust and gas pile up in front of the jets, which clear paths through nebular clouds like snowplows. One vital ingredient for baby stars, molecular hydrogen, gets swept up by these jets and is visible in Webb’s infrared images.

“Jets like these are signposts for the most exciting part of the star formation process,” said study co-author Nathan Smith of the University of Arizona. “We only see them during a brief window of time when the protostar is actively accreting.”

The accretion period of early star formation has been especially difficult for astronomers to study because it is fleeting — usually just a few thousand years in the earliest portion of a star’s multimillion-year childhood.

Study co-author Jon Morse of the California Institute of Technology said jets like those discovered in the study “are only visible when you embark on that deep dive — dissecting data from each of the different filters and analyzing each area alone.

“It’s like finding buried treasure,” Morse said.

Reiter said the size of the Webb telescope also played a role in the discovery.

“It's just a huge light bucket,” Reiter said. “That lets us see smaller things that we might have missed with a smaller telescope. And it also gives us really good angular resolution. So we get a level of sharpness that allows us to see relatively small features, even in faraway regions.”

The Webb Space Telescope program is led by NASA in partnership with the European Space Agency (ESA) and the Canadian Space Agency (CSA). The telescope’s science and mission operations are led by the Space Telescope Science Institute (STScI) in Baltimore.

The research was supported by NASA (NAS 5-0312, NAS 5–26555), STScI and a Dorothy Hodgkin Fellowship from the UK’s Royal Society.

-30-

Matter flows away from the poles of newborn stars in fast-moving columns that plow through nebular clouds. Gas and dust pile up in front of these outflows, forming waves called “bow shocks” in much the same way that bow waves form at the leading edge of seagoing ships. This false-color infrared image from the James Webb Space Telescope shows bow shocks of molecular hydrogen (red) streaming away from newborn stars in a star-forming region called the Cosmic Cliffs in the southern constellation Carina.

CREDIT

Image courtesy of NASA, ESA, CSA and STScI


Peer-reviewed paper:

“Deep diving off the ‘Cosmic Cliffs’: previously hidden outflows in NGC 3324 revealed by JWST” | Monthly Notices of the Royal Astronomical Society | DOI: 10.1093/mnras/stac2820

Megan Reiter, Jon A. Morse, Nathan Smith, Thomas J. Haworth, Michael A. Kuhn and Pamela D. Klaassen

https://doi.org/10.1093/mnras/stac2820

High-resolution IMAGES are available for download at:

https://news-network.rice.edu/news/files/2022/12/1215_COSMIC-f2a-lg.jpg
CAPTION: Astronomers from Rice University and other organizations dug deep into the data from this near-infrared image, one of the first taken by NASA’s James Webb Space Telescope. The image shows a star-forming region in the constellation Carina known as the Cosmic Cliffs. Many newborn stars in such regions are shrouded in thick clouds of dust. Webb’s infrared camera penetrated the dust, allowing astronomers to discover telltale signs of two dozen infant stars that hadn’t been previously detected. (Image courtesy of NASA, ESA, CSA and STScI)

https://news-network.rice.edu/news/files/2022/12/1215_COSMIC-mr9Fit-lg.jpg
CAPTION: Rice University astronomer Megan Reiter led a “deep dive” study of the earliest images from the James Webb Space Telescope. The research revealed telltale signs of two dozen previously uncataloged young stars in the star cluster NGC 3324 in the constellation Carina. (Photo by Jeff Fitlow/Rice University)

https://news-network.rice.edu/news/files/2022/12/1215_COSMIC-f2b-lg.jpg
CAPTION: Matter flows away from the poles of newborn stars in fast-moving columns that plow through nebular clouds. Gas and dust pile up in front of these outflows, forming waves called “bow shocks” in much the same way that bow waves form at the leading edge of seagoing ships. This false-color infrared image from the James Webb Space Telescope shows bow shocks of molecular hydrogen (red) streaming away from newborn stars in a star-forming region called the Cosmic Cliffs in the southern constellation Carina. (Image courtesy of NASA, ESA, CSA and STScI)

Related stories:

Gemini South’s high-def version of ‘A Star is Born’ – Oct. 5, 2020
https://news.rice.edu/news/2020/gemini-souths-high-def-version-star-born

Moon-forming disk discovered around distant planet - July 11, 2019
https://news2.rice.edu/2019/07/11/moon-forming-disk-discovered-around-distant-planet/

Direct from distant planet: Spectral clues to puzzling paradox – June 10, 2019
https://news2.rice.edu/2019/06/10/direct-from-distant-planet-spectral-clues-to-puzzling-paradox/

Carina Nebula survey reveals details of star formation – March 9, 2015
https://news2.rice.edu/2015/03/09/carina-nebula-survey-reveals-details-of-star-formation/

Hubble movies reveal solar-system-sized traffic jams – Aug. 31, 2011
https://news2.rice.edu/2011/09/07/hubble-movies-reveal-solar-system-sized-traffic-jams/

This release can be found online at news.rice.edu.

Follow Rice News and Media Relations via Twitter @RiceUNews.

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation’s top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 4,240 undergraduates and 3,972 graduate students, Rice’s undergraduate student-to-faculty ratio is just under 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for lots of race/class interaction and No. 1 for quality of life by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger’s Personal Finance.

JWST PEARLS project unveils exquisite views of distant galaxies

Peer-Reviewed Publication

ARIZONA STATE UNIVERSITY


The press release and accompanying multimedia are available online on ASU News here

For decades, the Hubble Space Telescope and ground-based telescopes have provided us with spectacular images of galaxies. This all changed when the James Webb Space Telescope (JWST) launched in December 2021 and successfully completed commissioning during the first half of 2022. For astronomers, the universe, as we had seen it, is now revealed in a new way never imagined by the telescope's Near-Infrared Camera(NIRCam) instrument.  

The NIRCam is Webb's primary imager that covers the infrared wavelength range from 0.6 to 5 microns. NIRCam detects light from the earliest stars and galaxies in the process of formation, the population of stars in nearby galaxies, as well as young stars in the Milky Way and Kuiper Belt objects. 

The Prime Extragalactic Areas for Reionization and Lensing Science, or PEARLS, project is the subject of a recent study published in Astronomical Journal by a team of researchers, including Arizona State University School of Earth and Space Exploration Regents Professor Rogier Windhorst, Research Scientist Rolf Jansen, Associate Research Scientist Seth Cohen, Research Assistant Jake Summers and Graduate Associate Rosalia O'Brien, along with the contribution of many other researchers.  

For researchers, the PEARLS program's images of the earliest galaxies show the amount of gravitational lensing of objects in the background of massive clusters of galaxies, allowing the team to see some of these very distant objects. In one of these relatively deep fields, the team has worked with stunning multicolor images to identify interacting galaxies with active nuclei. 

Windhorst and his team's data show evidence for giant black holes in their center where you can see the accretion disc — the stuff falling into the black hole, shining very brightly in the galaxy center. Plus, lots of galactic stars show up like drops on your car's windshields — like you're driving through intergalactic space. This colorful field is straight up from the ecliptic plane, the plane in which the Earth and the moon, and all the other planets, orbit around the sun.  

"For over two decades, I've worked with a large international team of scientists to prepare our Webb science program," Windhorst said. "Webb's images are truly phenomenal, really beyond my wildest dreams. They allow us to measure the number density of galaxies shining to very faint infrared limits and the total amount of light they produce. This light is much dimmer than the very dark infrared sky measured between those galaxies." 

The first thing the team can see in these new images is that many galaxies that were next to or truly invisible to Hubble are bright in the images taken by Webb. These galaxies are so far away that the light emitted by stars has been stretched. 

The team focused on the North Ecliptic Pole time domain field with the Webb telescope — easily viewed due to its location in the sky. Windhorst and the team plan to observe it four times.

The first observations, consisting of two overlapping tiles, produced an image that shows objects as faint as the brightness of 10 fireflies at the distance of the moon (with the moon not there). The ultimate limit for Webb is one or two fireflies. The faintest reddest objects visible in the image are distant galaxies that go back to the first few hundred million years after the Big Bang.

For most of Jansen's career, he's worked with cameras on the ground and in space, where you have a single instrument with a single camera that produces one image. Now scientists have an instrument that has not just one detector or one image coming out of it, but 10 simultaneously. For every exposure NIRCam takes, it gives 10 of these images. That's a massive amount of data, and the sheer volume can be overwhelming. 

To process that data and channel it through the analysis software of collaborators around the globe, Summers has been instrumental. 

“The JWST images far exceed what we expected from my simulations prior to the first science observations,” Summers said. “Analyzing these JWST images, I was most surprised by their exquisite resolution.” 

Jansen’s primary interest is to figure out how galaxies like our own Milky Way came to be. And the way to do that is by looking far back in time at how galaxies came together, seeing how they evolved, effectively, and so tracing the path from the Big Bang to people like us.  

"I was blown away by the first PEARLS images," Jansen said. "Little did I know, when I selected this field near the North Ecliptic Pole, that it would yield such a treasure trove of distant galaxies, and that we would get direct clues about the processes by which galaxies assemble and grow — I can see streams, tails, shells and halos of stars in their outskirts, the leftovers of their building blocks." 

Third-year astrophysics graduate student O'Brien designed algorithms to measure faint light between the galaxies and stars that first catch our eye. 

"The diffuse light that I measured in between stars and galaxies has cosmological significance, encoding the history of the universe," O'Brien said. "I feel fortunate to start my career right now — JWST data is like nothing we have ever seen, and I'm excited about the opportunities and challenges it offers." 

“I expect that this field will be monitored throughout the JWST mission, to reveal objects that move, vary in brightness or briefly flare up, like distant exploding supernovae or accreting gas around black holes in active galaxies,” Jansen said.

 

ASU press contact:   

Kim Baptista, 707-479-0311, Kim.baptista@asu.edu

 

###

Economic behaviour not influenced by gender or biological sex, study finds

Gender and sex assigned at birth are not as decisive in economic decision-making as previously thought

Peer-Reviewed Publication

UNIVERSITY OF EXETER

Gender and sex assigned at birth are not as decisive in economic decision-making as previously thought, a new study finds.

A new study published in Scientific Reports is the first analysis of transgender and cisgender economic behaviour, and the first to consider whether sex assigned at birth plays a significant part in economic decisions.

Helena Fornwagner and Brit Grosskopf from the University of Exeter Business School and Alexander Lauf, Vanessa Schöller, and Silvio Städter (University of Regensburg) have for the first time investigated the role of gender identity and biological sex in economic decision-making.  

The researchers explored whether being transgender or cisgender impacted factors that could influence whether we compete with others in applying for a new job, investing in a risky asset or donating to charity.

In a controlled experimental study featuring 780 participants, with around half identifying as transgender, they hypothesised that if gender identity does determine levels of competitiveness, risk-taking or altruism with money, then those with the same gender identity (cis men and trans men, and cis women and trans women) will make similar decisions. Those with a different gender identity would make significantly different economic decisions. Moreover, it was suggested that participants having the same biological sex (cismen and transwomen, and ciswomen and transmen) would behave comparably.

The researchers used a series of well-known economic experiments to determine how competitive the participants were with money, their willingness to take risks and how willing they were to give to charity. Before making any decisions, the participants completed a word search priming exercise that subconsciously assigned them a masculine, feminine or gender-neutral identity by asking them to find gender-specific words.

Using their study design, the researchers first test for a correlation impact of gender and sex by comparing the behaviour of cis-gender men, cis women, trans men and trans women. Second, the priming intervention enabled to control for causal inferences about gender and behaviour.

But in contrast to previous studies that have established links between gender and economic behaviour, the researchers found that gender and biological sex actually make no significant difference to our economic decisions.

Part of their rationale for this unexpected finding is that educational initiatives and a greater awareness of gender equality in private and professional settings have narrowed any economic behavioural differences, which were first established in studies almost two decades ago.

Dr Fornwagner said: “Gender has long been reported to be a driving factor in domains such as competitiveness, risk-taking and altruism, but our study is the first to ask how much can be associated with gender, and how much is based on the biological sex people are endowed with.

“Despite the partly unexpected findings that led us to conclude that the role of gender and sex is not as decisive for economic behaviour as previously assumed, we believe there are several important take-aways from this study.“

“Transgender individuals have become a more and more visible part of society. Thus, we think it is crucial to understand their economic behaviour and essential to expand experimental economic research to all groups summarised under the LGBTQ+ flag to acknowledge the colourful society we are already part of also in our scientific research.”

On the robustness of gender differences in economic behavior” is published in Scientific Reports.

Once a terrorist, always a terrorist?

Study examines the UN’s terrorist list

Peer-Reviewed Publication

MARTIN-LUTHER-UNIVERSITÄT HALLE-WI

At the United Nations, an ombudsperson reviews who is on the list of terrorists from Al Qaeda and the Islamic State. If someone feels that they have been wrongly placed on the list and should be removed, they can request that their case should be reviewed. Since the establishment of the office in 2010, 63 people have been struck off the list on the basis of recommendations made by the ombudsperson. Those on the list are subjected to far-reaching sanctions, for example travel bans and the freezing of bank accounts. Dr Andrej Lang, a legal scholar from Martin Luther University Halle-Wittenberg (MLU), takes stock of this issue in the American Journal of International Law.

The Office of the Ombudsperson for the United Nations’ "1267 Sanctions Regime" was introduced in 2010 - under pressure from the European Court of Justice. The regime was established by the UN Security Council in 1999 to combat terrorism by the Taliban and Al-Qaeda. Its aim was to target members and supporters of terrorist organisations. The Taliban were later removed from the regime and the so-called Islamic State (ISIL) was added. "International law has long permitted the Security Council to take economic sanctions against individual countries in order to maintain or restore international peace and security. However, these measures always affect an entire nation and its population. The sanctions regime was designed to allow taking targeted actions against individuals," explains legal scholar Dr Andrej Lang from MLU. The Security Council can decide whether individuals should be subjected to far-reaching sanctions. "When a person is placed on this list, all United Nations Member States are obliged to freeze that person’s accounts and restrict their freedom of movement by banning them from leaving the country," Lang adds. The measures aim to curb the financing of terrorism and thus prevent terrorist attacks. 

However, according to Lang, the process for putting people on this list is problematic. The decisions are made by a UN Security Council committee that is staffed by diplomats. Sometimes a Member State will allude to confidential documents created by their secret service without submitting these to the other Member States. Even more problematic is that not everyone who is sanctioned has been notified directly that their name is on the list. "There have been cases where a person suddenly could no longer pay his rent because his account had been frozen. That can derail his entire life," explains Lang. For his new study, the scholar examined the importance of the office of the ombudsperson and its work. It is an institution that persons can turn to if they believe they have been wrongly placed on the list. In addition to conducting an extensive review of the literature and publicly available UN documents, Lang also performed numerous interviews with diplomats, lawyers representing people on the list, and the three former ombudspersons. He used this material to produce the most comprehensive assessment of the ombudsperson’s role to date and placed its work within the current legal discourse on international dispute settlement and security politics. 

When a person on the list approaches the ombudsperson, she will start an investigation. At the end of these proceedings, the ombudsperson recommends whether the person should remain on or be removed from the list. This recommendation can be overruled only if all 15 members of the Sanctions Committee vote against it, or if the case is referred to the Security Council - neither of which has happened yet. "This gives the ombudsperson a strong recommendation power," says Lang. Around 450 people have been placed on the terrorist list since it was first introduced, and 105 of these people have initiated proceedings with the ombudsperson. According to Lang, most of these cases have been resolved. In most instances, a recommendation is made to remove the person from the list and the UN member states have so far always complied with this recommendation except in one case. "This is surprising since, in many cases, a number of states are convinced that the people deserved to remain on the list," says Lang. The researcher notes that the sheer amount of people removed from the list does not necessarily point to a serious flaw in the sanctions regime: "In the first few years, some people were wrongly placed on the terrorist list. However, if you look at the list now, for most people it seems justifiable that they were originally put on the list because they were or are active for al-Qaida or the ISIL." However, after a certain amount of time, this status has to be scrutinised. This applies, for example, to people who were convicted by a national court and have served their prison sentences - but remain on the list. 

Lang believes the work of the ombudsperson embodies a new trend in international law. "In the coming decades, it is likely that fewer international courts will be established than in the era following the Cold War. While the West’s influence wains, states like China and India are gaining in geopolitical influence, yet these states are not keen on creating such institutions. Under these conditions of a changing world order, dispute settlement bodies such as an ombudsperson constitute a compromise that may provide a better solution than it would initially appear - even if they do not always meet our Western standards for the rule of law," concludes Lang. 

Study: Lang A. Alternatives to adjudication in international law. A case study of the ombudsperson to the ISIL and Al-Qaida sanctions regime of the UN security council. American Journal of International Law (2022). doi: 10.1017/ajil.2022.81

Measuring times in billionths of a billionth of a second

Peer-Reviewed Publication

ULTRAFAST SCIENCE

Schematics of the experimental setup for Gouy phase interferometer. 

IMAGE: SCHEMATICS OF THE EXPERIMENTAL SETUP FOR GOUY PHASE INTERFEROMETER. THE SCHEMATIC OF THE EXPERIMENTAL SETUP IS SHOWN IN FIGURE 1. THERE ARE TWO MOVEABLE MOLECULAR JETS SEPARATED IN SPACE NEAR THE FOCUS OF THE DRIVING INFRARED LASER BEAM. THE PHASE DIFFERENCE BETWEEN HHG EMISSIONS FROM THE TWO JETS INCLUDES A CONTRIBUTION FROM THE GOUEY PHASE (THE ONLY CONTRIBUTION WHEN THE SAME GAS IS FLOWING IN BOTH JETS) AND AN ADDITIONAL PHASE SHIFT DUE TO THE DIFFERENT INTRINSIC HHG PHASES OF DIFFERENT SPECIES. TO EXTRACT THAT INTRINSIC PHASE SHIFT, THE HHG SPECTRA ARE MEASURED FIRST WITH THE SAME GASES IN BOTH JETS AND THEN WITH DIFFERENT GASES SWITCHED BETWEEN THE JETS. THIS PROCEDURE ALLOWS TO COMPLETELY REMOVE THE CONTRIBUTION OF THE GOUY PHASE AND THE EFFECT OF SLIGHTLY DIFFERENT INTENSITIES AT THE JETS’LOCATIONS. view more 

CREDIT: ULTRAFAST SCIENCE

How fast do electrons inside a molecule move? Well, it is so fast that it takes them just few attoseconds (1 as = 10-18 s or one billionth of billionth of a second) to jump from one atom to another. Blink and you missed it – millions of billions of times. So measuring such ultrafast processes is a daunting task. 

Scientists at the Australian Attosecond Science Facility and the Centre for Quantum Dynamics of Griffith University in Brisbane Australia, led by Professor Robert Sang and Professor Igor Litvinyuk have developed a novel interferometric technique capable of measuring time delays with zeptosecond (a trillionth of a billionth of a second) resolution. 

They have used this technique to measure the time delay between extreme ultraviolet light pulses emitted by two different isotopes of hydrogen molecules – H2 and D2 – interacting with intense infrared laser pulses. 

This delay was found to be less than three attoseconds (one quintillionth of a second long) and is caused by slightly different motions of the lighter and heavier nuclei. 

This study has been published in Ultrafast Science, a new Science Partner Journal.

The first author Dr Mumta Hena Mustary explains: “Such unprecedented time resolution is achieved via an interferometric measurement – overlapping the delayed light waves and measuring their combined brightness.” 

The light waves themselves were generated by molecules exposed to intense laser pulses in the process called high harmonic generation (HHG). 

HHG occurs when an electron is removed from a molecule by a strong laser field, is accelerated by the same field and then recombines with the ion giving up the energy in the form of extreme ultraviolet (XUV) radiation. Both intensity and phase of that XUV HHG radiation are sensitive to exact dynamics of the electron wavefunctions involved in this process – all different atoms and molecules emit HHG radiation differently. 

While it is relatively straightforward to measure spectral intensity of HHG – a simple grating spectrometer can do that – measuring HHG phase is a far more difficult task. And the phase contains the most relevant information about the timing of various steps in the emission process. 

To measure this phase, it is usual to perform a so-called interferometric measurement when two replicas of the wave with finely controlled delay are made to overlap (or interfere) with each other. They can interfere constructively or destructively depending on the delay and relative phase difference between them. 

Such measurement is performed by a device called an interferometer. It is very difficult to build an interferometer for XUV light, in particular to produce and maintain a stable, known and finely tuneable delay between two XUV pulses. 

The Griffith researchers solved this problem by taking advantage of the phenomenon known as the Gouy phase – when phase of a light wave is shifted a certain way while going through a focus. 

For their experiments the researchers used two different isotopes of molecular hydrogen – the simplest molecule in nature. The isotopes – light (H2) and heavy (D2) hydrogen – differ only in mass of nuclei – protons in H2 and deuterons in D2. Everything else including the electronic structure and energies are identical. 

Due to their larger mass the nuclei in D2 move slightly slower then those in H2. Because nuclear and electronic motions in molecules are coupled, nuclear motion affects the dynamics of the electron wavefunctions during the HHG process resulting in a small phase shift ΔφH2-D2 between the two isotopes. 

This phase shift is equivalent to a time delay Δt = ΔφH2-D2 /ω where ω is the frequency of the XUV wave. The Griffith scientists measured this emission time delay for all the harmonics observed in the HHG spectrum – it was nearly constant and slightly below 3 attoseconds. 

To understand their result the Griffith researchers were supported by theorists at Shanghai Jiao Tong University in Shanghai, China, led by Professor Feng He. 

The SJTU scientists used the most advanced theoretical methods to comprehensively model the HHG process in the two isotopes of molecular hydrogen including all degrees of freedom for nuclear and electronic motion at various levels of approximation. 

Their simulation reproduced experimental results well, and this agreement between theory and experiment gave the team confidence that the model captured the most essential features of the underlying physical process, so adjusting the model’s parameters and levels of approximation can determine the relative importance of various effects. 

While the actual dynamics is quite complex, it was found that two-centre interference during the electron recombination step is the dominant effect.
“Because hydrogen is the simplest molecule in nature and it can be modelled theoretically with high accuracy it was used in these proof-of-principle experiments for benchmarking and validation of the method,” Professor Litvinyuk said. 

“In the future, this technique can be used to measure ultrafast dynamics of various light-induced processes in atoms and molecules with unprecedented time resolution.”

Securing stable green energy under future extreme weather conditions

Climate is changing, and this will affect future energy systems based on solar and wind. But how? A new research project at Aarhus University will focus on this with a Sapere Aude grant from Independent Research Fund Denmark.

Grant and Award Announcement

AARHUS UNIVERSITY

Associate Professor Marta Victoria 

IMAGE: ASSOCIATE PROFESSOR MARTA VICTORIA view more 

CREDIT: CLAUS LILLEVANG, INDEPENDENT RESEARCH FUND DENMARK

In February 2021, the state of Texas was hit by wave of cold weather lasting two weeks. The event was without precedent, and the Texan energy supply, which is primarily dependent on wind, coal and gas, was completely unprepared for this kind of extreme weather.

Due to the cold weather, gas pipes and some wind turbines froze, and since this was accompanied by a period with low wind speeds, it caused two-week-long power outages in 4.5 million homes. The incident cost USD 24 billion and 262 people lost their lives. It was the worst winter-weather disaster ever in the US.

The European energy network is better interconnected and prepared to deal with such events, but in a future with increasing climate change and more extreme weather, such events will very likely occur again.

So how do we ensure a stable future energy system, if this will be based on energy sources that may well be sustainable and renewable, but that are also dependent on local weather conditions?

A new research project at Aarhus University will now try to explain.

"We can't build an energy system that takes account of everything. That would be extremely costly. So, what do we do if there is a long period without wind and without sun, and with a high demand for energy, and how can we adapt the system without over-dimensioning it? We need to find out what we have to be prepared for when the weather changes as a result of climate change," says Associate Professor Marta Victoria from the Department of Mechanical and Production Engineering at Aarhus University, who is heading the project.

She has just received a prestigious Sapere Aude-grant from Independent Research Fund Denmark (DFF) of DKK 6.2 million. Her project is called EXTREMES (Highly renewable energy systems under extreme weather events) and it aims to describe periods of extreme weather using statistics, and to design strategies to ensure that an energy system with a very high proportion of solar and wind energy is reliable, even under extreme weather conditions.

"How long will the worst period of low wind or solar production be? How many times a year will this happen? What is the worst period we can expect within a decade? Or a century? And what conditions should we adapt the system to? As a rule, there’s a backup, but in the project we’ll try to take into account situations where several adverse events happen at the same time, and where spatial and temporal fluctuations can be hard to predict," she says.

The project starts in spring 2023 and will run for four years.

Sapere Aude grants are awarded by Independent Research Fund Denmark to talented early-career researchers to enable them to develop and strengthen their own research ideas and establish themselves as research directors with the foundation's financial assistance.

This year, Independent Research Fund Denmark has awarded Sapere Aude grants to 41 researchers following 356 applications. Of these, 12 recipients are from Aarhus University: The 41 researchers share a total of DKK 247 million.