In a critical next step toward room-temperature superconductivity at ambient pressure, Paul Chu, Founding Director and Chief Scientist at the Texas Center for Superconductivity at the University of Houston (TcSUH), Liangzi Deng, research assistant professor of physics at TcSUH, and their colleagues at TcSUH conceived and developed a pressure-quench (PQ) technique that retains the pressure-enhanced and/or -induced high transition temperature (Tc) phase even after the removal of the applied pressure that generates this phase.
Pengcheng Dai, professor of physics and astronomy at Rice University and his group, and Yanming Ma, Dean of the College of Physics at Jilin University, and his group contributed toward successfully demonstrating the possibility of the pressure-quench technique in a model high temperature superconductor, iron selenide (FeSe). The results were published in the journal Proceedings of the National Academy of Science USA.
“We derived the pressure-quench method from the formation of the man-made diamond by Francis Bundy from graphite in 1955 and other metastable compounds,” said Chu. “Graphite turns into a diamond when subjected to high pressure at high temperatures. Subsequent rapid pressure quench, or removal of pressure, leaves the diamond phase intact without pressure.”
Chu and his team applied this same concept to a superconducting material with promising results.
“Iron selenide is considered a simple high-temperature superconductor with a transition temperature (Tc) for transitioning to a superconductive state at 9 Kelvin (K) at ambient pressure,” said Chu.
“When we applied pressure, the Tc increased to ~ 40 K, more than quadrupling that at ambient, enabling us to unambiguously distinguish the superconducting PQ phase from the original un-PQ phase. We then tried to retain the high-pressure enhanced superconducting phase after removing pressure using the PQ method, and it turns out we can.”
Dr. Chu and colleagues’ achievement brings scientists a step closer to realizing the dream of room-temperature superconductivity at ambient pressure, recently reported in hydrides only under extremely high pressure.
Superconductivity is a phenomenon discovered in 1911 by Heike Kamerlingh Onnes by cooling mercury below its transition Tc of 4.2 K, attainable with the aid of liquid helium, which is rare and expensive. The phenomenon is profound because of superconductor’s ability to exhibit zero resistance when electricity moves through a superconducting wire and its expulsion of magnetic field generated by a magnet. Subsequently, its vast potential in the energy and transportation sectors was immediately recognized.
To operate a superconducting device, one needs to cool it to below its Tc, which requires energy. The higher the Tc, the less energy needed. Therefore, raising the Tc with the ultimate goal of room temperature of 300 K has been the driving force for scientists in superconductivity research since its discovery.
In defiance of the then-prevailing belief that Tc could not exceed the 30’s K, Paul Chu , and colleagues discovered superconductivity in a new family of compounds at 93 K in 1987, achievable by the mere use of the inexpensive, cost-effective industrial coolant of liquid nitrogen. The Tc has continuously been raised since to 164 K by Chu et al. and other subsequent groups of scientists. Recently a Tc of 287 K was achieved by Dias et al. of Rochester University in carbon-hydrogen-sulfide under 267 gigapascal (GPa).
In short, the advancement of Tc to room temperature is indeed within reach. But for future scientific and technological development of hydrides, characterization of materials and fabrication of devices at ambient pressures is necessary.
“Our method allows us to make the material superconducting with higher Tc without pressure. It even allows us to retain at ambient the non-superconducting phase that exists only in FeSe above 8 GPa. There is no reason that the technique cannot be equally applied to the hydrides that have shown signs of superconductivity with a Tc approaching room temperature.”
The achievement inches the academic community closer toward room-temperature superconductivity (RTS) without pressure, which would mean ubiquitous practical applications for superconductors from the medical field, through power transmission and storage to transportation, with impacts whenever electricity is used.
Superconductivity as a means to improve power generation, storage and transmission is not a new idea, but it requires further research and development to become widespread before room temperature superconductivity becomes a reality. The capacity for zero electrical resistance means energy can be generated, transmitted and stored with no loss – an enormous low-cost advantage. However, current technology demands that the superconducting device be kept at severely low temperatures to retain its unique state, which still requires additional energy as an overhead cost, not to mention the potential hazard of the accidental failure of the cooling system. Hence, an RTS superconductor with no extra pressure to sustain its beneficial properties is a necessity to move forward with more practical applications.
The properties of superconductivity are also paving the way for a competitor to the famous bullet train seen throughout East Asia: a maglev train. Short for “magnetic levitation,” the first maglev train built in Shanghai in 2004 successfully broadened usage in Japan and South Korea and is under consideration for commercial operation in the US. At top speeds of 375 miles per hour, cross country flights see a quick competitor in the maglev train. A room temperature superconductor could help Elon Musk realize his dream of a “hyperloop” to travel at a speed of 1000 miles per hour.
This successful implementation of the PQ technique on room temperature superconductors discussed in Chu and Deng’s paper is critical in making superconductors possible for ubiquitous practical applications.
Now the riddle of RTS at ambient pressure is even closer to being solved.
This press release was produced by the University of Houston. The views expressed here are the author’s own.
Hot and dry: SPIRou reveals the atmosphere of hot Jupiter Tau Boötis b – News | Institute for Research on Exoplanets
Measuring the composition of the atmosphere of the hot Jupiter Tau Boötis b more precisely than ever, an iREx-led team of astronomers provides a better understanding of giant exoplanets.
Using the SPIRou spectropolarimeter on the Canada-France-Hawaii Telescope in Hawaii, a team led by Stefan Pelletier, a PhD student at Université de Montréal’s Institute for Research on Exoplanets (iREx), studied the atmosphere of the gas giant exoplanet Tau Boötis b, a scorching hot world that takes a mere three days to orbit its host star.
Their detailed analysis, presented in a paper published today in the Astronomical Journal, shows that the atmosphere of the gaseous planet contains carbon monoxide, as expected, but surprisingly no water, a molecule that was thought to be prevalent and should have been easily detectable with SPIRou.
Tau Boötis b is a planet that is 6.24 times more massive than Jupiter and eight times closer to its parent star than Mercury is to the Sun. Located only 51 light-years from Earth and 40 per cent more massive than the Sun, its star, Tau Boötis, is one of the brightest known planet-bearing stars, and is visible to the naked eye in the Boötes constellation.
Tau Boötis b was one of the first exoplanets ever discovered, in 1996, thanks to the radial velocity method, which detects the slight back-and-forth motion of a star generated by the gravitational tug of its planet. Its atmosphere had been studied a handful of times before, but never with an instrument as powerful as SPIRou to reveal its molecular content.
Searching for water
Assuming Tau Boötis b formed in a protoplanetary disk with a composition similar to that of our Solar System, models show that water vapour should be present in large quantities in its atmosphere. It should thus have been easy to detect with an instrument such as SPIRou.
“We expected a strong detection of water, with maybe a little carbon monoxide,” explained Pelletier. “We were, however, surprised to find the opposite: carbon monoxide, but no water.”
The team worked hard to make sure the results could not be attributed to problems with the instrument or the analysis of the data.
“Once we convinced ourselves the content of water was indeed much lower than expected on Tau Boötis b, we were able to start searching for formation mechanisms that could explain this,” said Pelletier.
Studying hot Jupiters to better understand Jupiter and Saturn
“Hot Jupiters like Tau Boötis b offer an unprecedented opportunity to probe giant planet formation”, said co-author Björn Benneke, an astrophysics professor and Pelletier’s PhD supervisor at UdeM. “The composition of the planet gives clues as to where and how this giant planet formed.”
The key to revealing the formation location and mechanism of giant planets is imprinted in their molecular atmospheric composition. The extreme temperature of hot Jupiters allows most molecules in their atmospheres to be in gaseous form, and therefore detectable with current instruments. Astronomers can thus precisely measure the content of their atmospheres.
“In our Solar System, Jupiter and Saturn are really cold,” said Benneke. “Some molecules such as water are frozen and hidden deep in their atmospheres; thus, we have a very poor knowledge of their abundance. Studying hot Jupiters provides a way to better understand our own giant planets. The low amount of water on Tau Boötis b could mean that our own Jupiter is also drier than we had previously thought.”
SPIRou: a unique instrument
Tau Boötis b is one of the first planets studied with the new SPIRou instrument since it was recently put into service at the Canada-France-Hawaii Telescope. This instrument was developed by researchers from several scientific institutions including UdeM.
“This spectropolarimeter can analyze the planet’s thermal light — the light emitted by the planet itself — in an unprecedentedly large range of colours, and with a resolution that allows for the identification of many molecules at once: water, carbon monoxide, methane, etc.” said co-author and iREx researcher Neil Cook, an expert on the SPIRou instrument.
The team spent 20 hours observing the exoplanet with SPIRou between April 2019 and June 2020.
“We measured the abundance of all major molecules that contain either carbon or oxygen,” said Pelletier. “Since they are the two most abundant elements in the universe, after hydrogen and helium, that gives us a very complete picture of the content of the atmosphere.”
Like most planets, Tau Boötis b does not pass in front of its star as it orbits around it, from Earth’s point of view. However, the study of exoplanet atmospheres has mostly been limited to “transiting” planets – those that cause periodic dips in the light of their star when they obscure part of their light.
“It is the first time that we get such precise measurements on the atmospheric composition of a non-transiting exoplanet,” said PhD student Caroline Piaulet, a co-author of the study.
“This work opens the door to studying in detail the atmospheres of a large number of exoplanets, even those that do not transit their star.”
A composition similar to Jupiter
Through their analysis, Pelletier and his colleagues were able to conclude that Tau Boötis b’s atmospheric composition has roughly five times as much carbon as that found in the Sun, quantities similar to that measured for Jupiter.
This may be a suggest that hot Jupiters could form much further from their host star, at distances that are similar to the giant planets in our Solar System, and have simply experienced a different evolution, which included a migration towards the star.
“According to what we found for Tau Boötis b, it would seem that, at least composition-wise, hot Jupiters may not be so different from our own Solar System giant planets after all,” concluded Pelletier.
About this study
“Where is the water? Jupiter-like C/H ratio but strong H2O depletion found on Tau Boötis b using SPIRou,” by Stefan Pelletier et al., was published July 28th, 2021 in the Astronomical Journal.
In addition to Stefan Pelletier, Björn Benneke, Neil Cook and Caroline Piaulet, the team includes Institute for research on exoplanets (iREx) members Antoine Darveau-Bernier, Anne Boucher, Louis-Philippe Coulombe, Étienne Artigau, David Lafrenière, Simon Delisle, Romain Allart, René Doyon, Charles Cadieux and Thomas Vandal, all based at Université de Montréal, and seven other co-authors from France, the United States, Portugal and Brazil.
Funding was provided by the the Technologies for Exo-Planetary Science (TEPS) CREATE program, the Fonds de recherche du Québec – Nature et technologies (FRQNT), the Natural Sciences and Engineering Research Council of Canada (NSERC), the Trottier Family Foundation and the French National Research Agency (ANR).
Scientists capture most-detailed radio image of Andromeda galaxy to date – UBC News
‘Disk of galaxy’ identified as region where new stars are born
Scientists have published a new, detailed radio image of the Andromeda galaxy – the Milky Way’s sister galaxy – which will allow them to identify and study the regions of Andromeda where new stars are born.
The study – which is the first to create a radio image of Andromeda at the microwave frequency of 6.6 GHz – was led by University of British Columbia physicist Sofia Fatigoni, with colleagues at Sapienza University of Rome and the Italian National Institute of Astrophysics. It was published online in Astronomy and Astrophysics.
“This image will allow us to study the structure of Andromeda and its content in more detail than has ever been possible,” said Fatigoni, a PhD student in the department of physics and astronomy at UBC. “Understanding the nature of physical processes that take place inside Andromeda allows us to understand what happens in our own galaxy more clearly – as if we were looking at ourselves from the outside.”
Prior to this study, no maps capturing such a large region of the sky around the Andromeda Galaxy had ever been made in the microwave band frequencies between one GHz to 22 GHz. In this range, the galaxy’s emission is very faint, making it hard to see its structure. However, it is only in this frequency range that particular features are visible, so having a map at this particular frequency is crucial to understanding which physical processes are happening inside Andromeda.
In order to observe Andromeda at this frequency, the researchers required a single-dish radio telescope with a large effective area. For the study, the scientists turned to the Sardinia Radio Telescope, a 64-metre fully steerable telescope capable of operating at high radio frequencies, located in Italy.
It took 66 hours of observation and consistent data analysis for the researchers to map the galaxy with high sensitivity.
They were then able to estimate the rate of star formation within Andromeda, and produce a detailed map that highlighted the ‘disk of the galaxy,’ as the region where new stars are born.
“By combining this new image with those previously acquired, we have made significant steps forward in clarifying the nature of Andromeda’s microwave emissions and allowing us to distinguish physical processes that occur in different regions of the galaxy,” said Dr. Elia Battistelli, a professor in the department of physics at Sapienza and coordinator of the study.
“In particular, we were able to determine the fraction of emissions due to thermal processes related to the early stations of new star formation, and the fraction of radio signals attributable to non-thermal mechanisms due to cosmic rays that spiral in the magnetic field present in the interstellar medium,” Fatigoni said.
For the study, the team also developed and implemented software that allowed them to test new algorithms to identify never-before-examined lower emission sources in the field of view around Andromeda at a frequency of 6.6 GHz.
From the resulting map, researchers were able to identify a catalog of about 100 ‘point sources’ including stars, galaxies and other objects in the background of Andromeda.
Interview language(s): English, Italian
Note for reporters: Sofia Fatigoni is based in Rome, Italy and is available for interviews until 3 p.m. PST.
To help chart the cosmos, Western space researchers turn to crowd sourcing – CBC.ca
Western University researchers have tapped the help of hundreds of amateur and professional astronomers in an effort to make sure no meteor is unable to slip by the Earth undetected.
To do that, they’re relying on the observations taken from 450 cameras in 30 different countries manned by “enthusiastic amateur astronomers” made up of professional and citizen scientists.
That data is then sent to Western University as part of what’s called the Global Meteor Network (GMN), headed by Denis Vida.
“So we have a lot of enthusiastic amateur astronomers, citizen scientists and also professionals that build, operate and maintain these cameras,” Vida told CBC’s Chris dela Torre during Afternoon Drive. “And every night they inspect the data set and send their data to a central server here at the University of Western Ontario.”
It’s not just about observing meteors – it’s about tracking what’s left of the ones that make it to the earth’s surface too.
“So we also observe a meteorite dropping fireballs,” said Vida. “They’re quite rare over an area of let’s say the country the size of France or Spain. Could only expect two to three of those fireballs a year that drop more than, let’s say, 300 grams of meteorites on the ground.”
“So because these events are very rare, it is important to observe 24/7.”
Vida explained that when one of their cameras spot one of them, they collect the data and find its location so they can retrieve what’s left for analysis – and analysis needs to happen quickly.
“There are certain things in them, like some radionuclide to decay very quickly, but those can tell us how old the meteorite is, how long it was after it was ejected from the parent asteroid that it fell on the ground,” he said.
Vida explained that what ends up on the ground are just “several kilograms of materials” by the time they reach the earth’s surface. They aren’t hot either. They cool down on their descent.
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