Scientists Capture Candid Snapshots of Electrons Harvesting Light at the Atomic Scale (Quantum)

Berkeley Lab scientists gain insight into charge generation induced by light; could enable the design of better solar fuels devices.

A research team led by Berkeley Lab has gained important new insight into electrons’ role in the harvesting of light for solar fuels. (Credit: Surat Sangwato/Shutterstock)

In the search for clean energy alternatives to fossil fuels, one promising solution relies on photoelectrochemical (PEC) cells – water-splitting, artificial-photosynthesis devices that turn sunlight and water into solar fuels such as hydrogen.

In just a decade, researchers in the field have achieved great progress in the development of PEC systems made of light-absorbing gold nanoparticles – tiny spheres just billionths of a meter in diameter – attached to a semiconductor film of titanium dioxide nanoparticles (TiO2 NP). But despite these advancements, researchers still struggle to make a device that can produce solar fuels on a commercial scale.

Now, a team of scientists led by the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has gained important new insight into electrons’ role in the harvesting of light in gold/TiO2 NP PEC systems. The scientists say that their study, recently published in the Journal of Physical Chemistry Letters, can help researchers develop more efficient material combinations for the design of high-performance solar fuels devices.

“By quantifying how electrons do their work on the nanoscale and in real time, our study can help to explain why some water-splitting PEC devices did not work as well as hoped,” said senior author Oliver Gessner, a senior scientist in Berkeley Lab’s Chemical Sciences Division.

And by tracing the movement of electrons in these complex systems with chemical specificity and picosecond (trillionths of a second) time resolution, the research team members believe they have developed a new tool that can more accurately calculate the solar fuels conversion efficiency of future devices.

Electron-hole pairs: A productive pairing comes to light

Researchers studying water-splitting PEC systems have been interested in gold nanoparticles’ superior light absorption due to their “plasmonic resonance” – the ability of electrons in gold nanoparticles to move in sync with the electric field of sunlight.

“The trick is to transfer electrons between two different types of materials – from the light-absorbing gold nanoparticles to the titanium-dioxide semiconductor,” Gessner explained.

Illustration of a PEC model system with 20-nanometer gold nanoparticles attached to titanium dioxide.(Credit: Berkeley Lab)

When electrons are transferred from the gold nanoparticles into the titanium dioxide semiconductor, they leave behind “holes.” The combination of an electron injected into titanium dioxide and the hole the electron left behind is called an electron-hole pair. “And we know that electron-hole pairs are critical ingredients to enabling the chemical reaction for the production of solar fuels,” he added.

But if you want to know how well a plasmonic PEC device is working, you need to learn how many electrons moved from the gold nanoparticles to the semiconductor, how many electron-hole pairs are formed, and how long these electron-hole pairs last before the electron returns to a hole in the gold nanoparticle. “The longer the electrons are separated from the holes in the gold nanoparticles – that is, the longer the lifetime of the electron-hole pairs – the more time you have for the chemical reaction for fuels production to take place,” Gessner explained.

To answer these questions, Gessner and his team used a technique called “picosecond time-resolved X-ray photoelectron spectroscopy (TRXPS)” at Berkeley Lab’s Advanced Light Source (ALS) to count how many electrons transfer between the gold nanoparticles and the titanium-dioxide film, and to measure how long the electrons stay in the other material. Gessner said his team is the first to apply the X-ray technique for studying this transfer of electrons in plasmonic systems such as the nanoparticles and the film. “This information is crucial to develop more efficient material combinations.”

An electronic ‘count’-down with TRXPS

Using TRXPS at the ALS, the team shone pulses of laser light to excite electrons in 20-nanometer (20 billionths of a meter) gold nanoparticles (AuNP) attached to a semiconducting film made of nanoporous titanium dioxide (TiO2).

The team then used short X-ray pulses to measure how many of these electrons “traveled” from the AuNP to the TiO2 to form electron-hole pairs, and then back “home” to the holes in the AuNP.

“When you want to take a picture of someone moving very fast, you do it with a short flash of light – for our study, we used short flashes of X-ray light,” Gessner said. “And our camera is the photoelectron spectrometer that takes short ‘snapshots’ at a time resolution of 70 picoseconds.”

The TRXPS measurement revealed a few surprises: They observed two electrons transfer from gold to titanium dioxide – a far smaller number than they had expected based on previous studies. They also learned that only one in 1,000 photons (particles of light) generated an electron-hole pair, and that it takes just a billionth of a second for an electron to recombine with a hole in the gold nanoparticle.

Altogether, these findings and methods described in the current study could help researchers better estimate the optimal time needed to trigger solar fuels production at the nanoscale.

“Although X-ray photoelectron spectroscopy is a common technique used at universities and research institutions around the world, the way we expanded it for time-resolved studies and used it here is very unique and can only be done at Berkeley Lab’s Advanced Light Source,” said Monika Blum, a co-author of the study and research scientist at the ALS.

“Monika’s and Oliver’s unique use of TRXPS made it possible to identify how many electrons on gold are activated to become charge carriers – and to locate and track their movement throughout the surface region of a nanomaterial – with unprecedented chemical specificity and picosecond time resolution,” said co-author Francesca Toma, a staff scientist at the Joint Center for Artificial Photosynthesis (JCAP) in Berkeley Lab’s Chemical Sciences Division. “These findings will be key to gaining a better understanding of how plasmonic materials can advance solar fuels.”

The team next plans to push their measurements to even faster time scales with a free-electron laser, and to capture even finer nanoscale snapshots of electrons at work in a PEC device when water is added to the mix.

References: Mario Borgwardt, Johannes Mahl, Friedrich Roth, Lukas Wenthaus, Felix Brauße, Monika Blum, Klaus Schwarzburg, Guiji Liu, Francesca M. Toma, and Oliver Gessner, “Photoinduced Charge Carrier Dynamics and Electron Injection Efficiencies in Au Nanoparticle-Sensitized TiO2 Determined with Picosecond Time-Resolved X-ray Photoelectron Spectroscopy”, J. Phys. Chem. Lett. 2020, 11, 14, 5476–5481, 2020

Provided by University Of Berkeley

Shhh! These Tests Will Enable a Quieter Search for Dark Matter (Physics)

LUX-ZEPLIN collaboration publishes results showing radioactive background levels for experiment’s components, creates library for future rare event searches.

Brianna Mount at work in the Black Hills State University Underground Campus (BHUC) at Sanford Lab, where components of the LUX-ZEPLIN experiment were tested to better understand backgrounds of the materials.
Photo by Matthew Kapust.

The subatomic world just got a lot quieter for the LUX-ZEPLIN (LZ) dark matter experiment.

Currently being assembled on the 4850 Level, 4,850 feet below the surface at the Sanford Underground Research Facility (Sanford Lab), LZ will search for theoretical dark matter particles known as WIMPs, or weakly interacting massive particles.

In a paper accepted for publication in the European Physics Journal, the LZ collaboration shares the results of more than 1,200 assays – tests that describe the levels of radioactive decay of the LZ detector components – with the scientific community. These results also effectively create a library of resources for future experiments.

“This effort dramatically increases our ability to seek out dark matter signals in our detector,” said Kevin Lesko, spokesperson for the LZ collaboration and lead for the effort to achieve a low radioactive background for the LZ experiment.

“The whole experiment participated in this effort; everyone understood the importance of achieving a very low background level and a strong background model,” he added. Lesko is also a senior scientist at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), the lead institution for the LZ project, which is supported by DOE’s Office of Science.

The paper, entitled “The LUX-ZEPLIN radioactivity and cleanliness control programs,” details the results of assays completed by the collaboration at the Black Hills State University Underground Campus (BHUC), Boulby Underground Germanium Suite (BUGS), and the Berkeley Low Background Facility (BLBF).

What’s that sound?

The quantum soundscape is a boisterous one.

A constant barrage of cosmic rays from our sun showers the Earth, reverberating through matter. Atoms decay and reconfigure. Protons pop free from one nucleus only to be picked up by another. Electrons, stripped from their orbit, are sent ricocheting through surrounding matter. And though we normally think of radiation in the context of X-ray machines and nuclear power sources, everything – from bananas to skin cells to dust – contributes to a constant hum of background radiation in our world.

Most of us are oblivious to this ongoing racket. Particle physicists are not.

Experiments searching for extremely rare particle interactions (like interactions with dark matter particles) are most bothered by this noise. When they tune their experiments to eavesdrop on the particle world, they get a deafening cacophony that obscures the very signal they want to hear. Physicists call this effect background.

Turning down the volume

Before looking for dark matter, LZ physicists needed to turn down the background volume.

First, LZ researchers constructed the experiment’s inner detector inside a class-1000 clean room, requiring everyone to wear a full body clean suit before entering. This prevented dust, a source of radioactive decay, from accumulating on the detector. During months of assembly, less than one gram of dust accumulated on the surface of the 5,000 pound, 9-foot-tall inner detector after remedial cleaning.

Researchers examine the foil-wrapped LUX-ZEPLIN inner detector that was assembled in a class-100 cleanroom in the Surface Assembly Lab at Sanford Lab. Photo by Matthew Kapust

Next, the detector was transported nearly a mile underground to the 4850 Level of Sanford Lab. There, the rock overburden shields the experiment from the Sun’s cosmic rays. In the underground cavern, they inserted the detector inside a water tank that will be filled with more than 200 tons of deionized water. This liquid shield will absorb radiation emanating from the cavern’s rock or other experiment support systems.

But what about the detector itself? How could researchers be sure the materials used to build the detector wouldn’t create backgrounds of their own?

Testing every component

“Early on, we decided we wanted the backgrounds in the experiment to be dominated by nature—by things we can’t eradicate, like neutrinos—not by the materials we were using to build the detector,” Lesko said.

The collaboration’s recent paper is the result of efforts to assay, or test, nearly every component that went into the detector.

“We required every subsystem to send in samples for testing,” Lesko said. “At this point, we’ve assayed every nut, every screw, every washer, every component. We either have a characteristic assay of the raw materials, or of the finished component.”

Of the 1,200 assays in the publication, 969 assays used high purity germanium (HP Ge) to examine the radiopurity of components. Roughly seventy percent of the HP Ge assays were completed by the BHUC on the 4850 Level of Sanford Lab. Working one sample at a time, researchers placed LZ’s components inside detectors for weeks at a time, quietly listening to and recording the noise they produced.

In the BHUC, this low background counter uses a high purity germanium detector to assay materials, telling researchers more about a given materials radiopurity or “quietness.” Photo by Matthew Kapust

“In the past five years, the majority of the samples counted at the BHUC have been for the LZ experiment,” said Brianna Mount, director of the BHUC. “This paper is the culmination of that effort, and it demonstrates what the BHUC is capable of doing for the scientific community.”

Using this process, researchers learned that some materials were 10 to 100 times more radioactive than others. This helped researchers make informed decisions when selecting materials. In some cases, they even worked with manufacturers to redesign components to have lower backgrounds. Finally, researchers tallied the collective backgrounds of all the components to better understand how much interference they can expect to see when they turn on the detector.

“This effort gives us a very strong prediction of the limits of the radioactive components as we try to decipher dark matter signals from backgrounds,” Lesko said.

The LZ dark matter experiment is being assembled inside a large water tank on the 4850 Level of Sanford Lab. LZ will search for theoretical dark matter particles, known as WIMPs. Photo by Nick Hubbard

Provided by Sanford Underground Research Facility

New Type Of Plastic Made From Reclaimed Waste (Material Science)

A new type of plastic made of reclaimed waste readily degrades in less than a year. The substance that will soon serve to manufacture and break down mainly disposable products in an ecofriendly way goes by the name of polyhydroxybutyrate. This innovative material can be produced on an industrial scale in a new process developed by the Fraunhofer Institute for Production Systems and Design Technology IPK and its partners.

Compounded and granulated polyhydroxybutyrate (PHB). © Fraunhofer IPK/Andy King

Everyday life devoid of plastics – that would be hard to imagine. They figure prominently in packaging and consumer goods, and are indispensable to industry applications such as automotive and medical engineering. Reuse and recycling of plastics from fossil resources is hardly common practice. On top of that, they degrade at a glacial pace and pollute the environment for a long time to come. The great patches of plastic waste floating on our oceans attest to their power to pollute. Plastic bottles and bags despoil beaches and, in many places, entire stretches of land.

The Fraunhofer IPK team developed this injection molding tool to replicate prototype components made of polyhydroxybutyrate. © Fraunhofer IPK/Andy King

The Bioeconomy International research initiative

The need for global recycling strategies is urgent, given plastics’ heavy use all over the world. More and more governments are resorting to bans to curb the swelling tide of plastic waste. A viable option to replace fossil-based plastics on a large scale has yet to be found. This is why the German Federal Ministry of Education and Research (BMBF) launched the “Bioökonomie International” (Bioeconomy International) research initiative in close cooperation with Fraunhofer IPK, the Department of Bioprocess Technology of the Technical University of Berlin, regional industrial partners and international research partners from Malaysia, Columbia and the USA. These researchers are developing a method of manufacturing polymers without drawing on premium resources such as mineral, palm and rapeseed oils, the production of which is very detrimental to the environment.

A new plastic much like polypropylene

This new process turn industrial leftovers such as waste fats that contain a lot of mineral residue into polyhydroxybutyrate (PHB). Microorganisms can metabolize these residues in special fermentation processes. They deposit the PHB in their cells to store energy. “Once the plastic has been dissolved from the cell, it is still not ready for industrial use, because the hardening process takes far too long,“ says Christoph Hein, head of the Microproduction Technology department at Fraunhofer IPK. The raw material has to be mixed with chemical additives downstream in post-production stages. For example, the research team adjusted the plasticizing and processing parameters to trim the recrystallization time to fit the timing of industrial processing. The resultung biopolymer’s properties resemble those of polypropylene. But unlike PP, this plastic degrades fully in six to twelve months.

In this method of producing plastic, microorganisms synthesize the entire polymer in a biotechnical process. “To this end, we convert biogenic residues such as waste fats into polyesters that can be put to technical use,” says Hein. The researcher and his team opted for microorganisms, genetically modified with molecular methods, to serve as biocatalysts. With the help of chemical purification processes and an extensively optimized material, they have been able to develop a novel family of materials that satisfy the demands of technical plastics.

No petroleum-based synthetic components needed

The new process not only dispenses with petroleum-based synthetic components altogether; it also enables green plastic alternatives. Naturally occurring microorganisms can break down these newly developed plastics, so they need not be subjected to the special conditions that serve to degrade matter in industrial composting plants. They offer an ecofriendly alternative to making and degrading single-use products and other disposable items.

The process also lends itself to producing high-quality plastic parts for certain technical applications and periods of use. The specifications for this sort of product are more demanding. They may have to exhibit specific geometric tolerances and surface qualities or be reproducible with great precision. The researchers developed highly specialized replication processes to meet these requirements.

Provided by Fraunhofer

We Haven’t Find Evidence Of Gravitational Wave Lensing Yet (Physics)

Gravitational wave scientists looking for evidence of ‘lensing’, in which the faintest gravitational wave signals become amplified, are unlikely to make these detections in the near future according to new analysis by scientists at the University of Birmingham.

Credit: University of Birmingham

A team in the University’s School of Physics and Astronomy and the Institute for Gravitational Wave Astronomy has analysed currently available gravitational wave data to predict that these elusive signals are likely to remain undetected by the instruments currently operated by the LIGO and Virgo Collaboration.

The existence of gravitational lensing was predicted by Einstein and is a well-recognised phenomenon in relation to light waves. Light emitted by distant objects in the Universe is bent by the gravitational pull of other massive objects, such as galaxies when the light source passes behind them. When detected by the earth’s telescopes, this distortion might make the light-emitting object seem larger or closer to earth than it actually is.

Scientists predict that the same will be true of signals from gravitational waves – but we won’t find them just yet. In a paper published in Physical Review Letters, the Birmingham team drew together available information on the sensitivity of the current observatories with another key ingredient – the as-yet undetected background – to predict the statistical likelihood of lensing events.

This background is composed of the potentially huge numbers of gravitational wave signals that can only be analysed by their statistical probability because they are too small or too far away to be detected individually.

The team predicted that in order to detect one signal significantly affected by lensing, the observing teams would need to collect at least tens of thousands of them.

Lead author Dr Riccardo Buscicchio explains: “The number of gravitational wave events detected by the LIGO/Virgo Consortium has already reached several dozen (many of them yet to be confirmed) and over the next few years these will expand into hundreds of new detections. As we start to accumulate gravitational wave statistics, it’s likely that we will start to see many new phenomena, so in principle, detecting gravitational lensing becomes more likely.

“In general, however, these events are particularly difficult to positively identify – it’s very hard to tell if the signal a is very distant one that has been amplified through lensing, or if it is simply closer and therefore easier to detect. Our analysis suggests not only that there is actually quite a low probability of seeing this phenomenon given the sensitivity of current instruments, but also that existing detections thought to be potential candidates are in fact unlikely to be examples of lensing.”

References: Riccardo Buscicchio, Christopher J. Moore, Geraint Pratten, Patricia Schmidt, Matteo Bianconi, and Alberto Vecchio, “Constraining the Lensing of Binary Black Holes from Their Stochastic Background”, Phys. Rev. Lett. 125, 141102 – Published 30 September 2020

Provided by University Of Birmingham

Physicists Developed A Mobile Radar Device To Quickly Find Buried People In Lage Areas (Physics)

Whether in an avalanche or in collapsed buildings: Buried people must be rescued as fast as possible. Radar devices can help with the search. To date, however, they have only been able to analyze small areas for vital signs. In the long run, though, new, mobile devices can be carried by helpers or mounted on drones to cover hectare-sized areas.

Breathing and pulse signals of a walking person measured by a MIMO radar from several meters away. © Fraunhofer FHR / Reinhold Herschel

Finding buried people under debris is difficult. But if you want to rescue survivors, time is critical. Radar can be a major help here: The equipment available to date, however, only allows for stationary operation. The system is set up at a certain spot from where it can check an area up to a distance of twenty to thirty meters – depending on the radar.

Pulse Measurable to Ninety-Nine Percent

A technology developed by Fraunhofer FHR can significantly increase the reach of these radar devices. This is made possible by a mobile radar device. In the future, rescue forces could carry this across a field of debris, or a drone equipped with the radar device could fly across the scene of the accident. This way, even hectare-sized areas could be searched effectively and quickly. In doing so, the radar device detects the pulse rate and the breathing frequency of buried people, separating these from arm and leg movements. And it does so with a high accuracy: It measures the pulse rate as accurately as 99%, as the comparison to portable pulse devices has shown.

The technology can also be used the other way around: By positioning the device at a stationary spot, vital signs of people moving in the area surrounding the device can be detected. This can make sense, for example, where there are numerous injured people needing first aid, for instance in a sports facility. The radar device can be used to capture the vital signs and match them to the respective injured persons. Who needs help most urgently? In this process, the algorithm primarily looks at changes: Is the heart fibrillating? Is the patient breathing very fast? Vital parameters are direction-dependent: When a person turns over, this has effects on his or her breathing. The changes in rhythm, while the breathing signal and the movement also overlap. The algorithm is able to break down these signals and show them separately.

The first algorithm is ready for use; the system has already been tested with a person walking past it at a distance of up to 15 meters. In the next steps, the system can be adjusted to different situations. Besides rescue services, one of these situations could be autonomous driving. Here, the ability to distinguish between living beings and other obstacles is fundamental for safety – a child running into the street calls for another evasive maneuver than a ball rolling into the street. The mobile radar is ideal for these questions as well.

Provided by Fraunhofer

Search For New Worlds From Home With NASA’s Planet Patrol Project (Astronomy)

Help NASA find exoplanets, worlds beyond our solar system, through a newly launched website called Planet Patrol. This citizen science platform allows members of the public to collaborate with professional astronomers as they sort through a stockpile of star-studded images collected by NASA’s Transiting Exoplanet Survey Satellite (TESS).

Credit: Nasa/Goddard

“Automated methods of processing TESS data sometimes fail to catch imposters that look like exoplanets,” said project leader Veselin Kostov, a research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the SETI Institute in Mountain View, California. “The human eye is extremely good at spotting such imposters, and we need citizen scientists to help us distinguish between the look-alikes and genuine planets.”

Volunteers will help determine which TESS snapshots include signals from potential planets and which ones show planet impersonators.

Video: Want to hunt the skies for uncharted worlds from home? Join Planet Patrol! Watch to learn how you can collaborate with professional astronomers and analyze images from NASA’s Transiting Exoplanet Survey Satellite (TESS) on your own. You’ll answer questions about each TESS image and help scientists figure out if they contain signals from new worlds or planetary imposters. Credits: NASA’s Goddard Space Flight Center/Conceptual Image Lab

TESS uses its four cameras to take full images of one patch of sky, called a sector, every 10 minutes for a month at a time. This long stare allows TESS to see when planets pass in front of their stars, or transit, and dim their light. Over the course of a year, TESS collects hundreds of thousands of snapshots, each containing thousands of possible planets – too many for scientists to examine without help.

Computers are very good at analyzing such data sets, but they’re not perfect, Kostov said. Even the most carefully crafted algorithms can fail when the signal from a planet is weak. Some of the most interesting exoplanets, like small worlds with long orbits, can be especially challenging. Planet Patrol volunteers will help discover such worlds and will contribute to scientists’ understanding of how planetary systems form and evolve throughout the universe.

Planets aren’t the only source of changes in starlight, though. Some stars naturally change brightness over time, for example. In other cases, a star could actually be an eclipsing binary, where two orbiting stars alternately transit or eclipse each other. Or there may be an eclipsing binary in the background that creates the illusion of a planet transiting a target star. Instrumental quirks can also cause brightness variations. All these false alarms can trick automated planet-hunting processes.

On the new website, participants will help Kostov and his team sift through TESS images of potential planets by answering a set of questions for each – like whether it contains multiple bright sources or if it resembles stray light rather than light from a star. These questions help the researchers narrow down the list of possible planets for further follow-up study.

Citizen scientists can dive even deeper by learning more about the star in each image and by engaging with the Planet Patrol community.

A Goddard summer intern recently helped discover the TESS mission’s first planet orbiting two stars through another citizen science program called Planet Hunters TESS, run by the University of Oxford.

“We’re all swimming through the same sea of data, just using different strokes,” said Marc Kuchner, the citizen science officer for NASA’s Science Mission Directorate. “Planet Hunters TESS asks volunteers to look at light curves, which are graphs of stars’ brightness over time. Planet Patrol asks them to look at the TESS image directly, although we plan to also include light curves for those images in the future.”

Planet Patrol is a collaboration between NASA, the SETI Institute in Mountain View, California, the Space Telescope Science Institute in Baltimore, and Zooniverse, a collaboration of scientists, software developers, and educators who collectively develop and manage citizen science projects on the internet. It is funded by the Sellers Exoplanet Environments Collaboration at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

TESS is a NASA Astrophysics Explorer mission led and operated by MIT in Cambridge, Massachusetts, and managed by NASA’s Goddard Space Flight Center. Additional partners include Northrop Grumman, based in Falls Church, Virginia; NASA’s Ames Research Center in California’s Silicon Valley; the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts; MIT’s Lincoln Laboratory; and the Space Telescope Science Institute in Baltimore. More than a dozen universities, research institutes, and observatories worldwide are participants in the mission.

Provided by NASA’s Goddard Space Flight Center

Hubble Watches Exploding Star Fade Into Oblivion (Astronomy)

When a star unleashes as much energy in a matter of days as our Sun does in several billion years, you know it’s not going to remain visible for long.

Astronomers using NASA’s Hubble Space Telescope captured the quick, fading celebrity status of a supernova, the self-detonation of a star. The supernova, called SN 2018gv, appears in the lower left portion of the frame as a blazing star located on the outer edge of spiral galaxy NGC 2525, located 70 million light-years away.
© NASA, ESA, and A. Riess (STScI/JHU) and the SH0ES team; acknowledgment: M. Zamani (ESA/Hubble)

Like intergalactic paparazzi, NASA’s Hubble Space Telescope captured the quick, fading celebrity status of a supernova, the self-detonation of a star. The Hubble snapshots have been assembled into a telling movie of the titanic stellar blast disappearing into oblivion in the spiral galaxy NGC 2525, located 70 million light-years away.

Hubble began observing SN 2018gv in February 2018, after the supernova was first detected by amateur astronomer Koichi Itagaki a few weeks earlier in mid-January. Hubble astronomers were using the supernova as part of a program to precisely measure the expansion rate of the universe — a key value in understanding the physical underpinnings of the cosmos. The supernova serves as a milepost marker to measure galaxy distances, a fundamental value needed for measuring the expansion of space.

Fig: SN 2018gv fades (IMAGE). Astronomers using NASA’s Hubble Space Telescope captured the quick, fading celebrity status of a supernova, the self-detonation of a star. The Hubble snapshots have been assembled into a telling movie of the titanic stellar blast disappearing into oblivion in the spiral galaxy NGC 2525, located 70 million light-years away. The supernova, named SN 2018gv, appears as a blazing star located on the galaxy’s outer edge. It initially outshines the brightest stars in the galaxy before fading out of sight. The time-lapse video consists of observations taken from February 2018 to February 2019. View animated GIF: NASA, ESA, and A. Riess (STScI/JHU) and the SH0ES team; acknowledgment: M. Zamani (ESA/Hubble)

In the time-lapse sequence, spanning nearly a year, the supernova first appears as a blazing star located on the galaxy’s outer edge. It initially outshines the brightest stars in the galaxy before fading out of sight.

“No Earthly fireworks display can compete with this supernova, captured in its fading glory by the Hubble Space Telescope,” said Nobel laureate Adam Riess, of the Space Telescope Science Institute (STScI) and Johns Hopkins University in Baltimore, leader of the High-z Supernova Search Team and the Supernovae H0 for the Equation of State (SH0ES) Team to measure the universe’s expansion rate.

The type of supernova seen in this sequence originated from a burned-out star — a white dwarf located in a close binary system — that is accreting material from its companion star. When the white dwarf reaches a critical mass, its core becomes hot enough to ignite nuclear fusion, turning it into a giant atomic bomb. This thermonuclear runaway process tears the dwarf apart. The opulence is short-lived as the fireball fades away.

Because supernovae of this type all peak at the same brightness, they are known as “standard candles,” which act as cosmic tape measures. Knowing the actual brightness of the supernova and observing its brightness in the sky, astronomers can calculate the distances of their host galaxies. This allows astronomers to measure the expansion rate of the universe. Over the past 30 years Hubble has helped dramatically improve the precision of the universe’s expansion rate.

Video: This video zooms into the barred spiral galaxy NGC 2525, located 70 million light-years away in the southern constellation Puppis. Roughly half the diameter of our Milky Way, it was discovered by British astronomer William Herschel in 1791 as a “spiral nebula.” The sharpness of the image increases as we zoom into the Hubble view. As we approach an outer spiral arm a Hubble time-lapse video is inserted that shows the fading light of supernova 2018gv. Hubble didn’t record the initial blast in January 2018, but for nearly one year took consecutive photos, from 2018 to 2019, that have been assembled into a time-lapse sequence. At its peak, the exploding star was as bright as 5 billion Suns. Credits: NASA, ESA, J. DePasquale (STScI), M. Kornmesser and M. Zamani (ESA/Hubble), A. Riess (STScI/JHU) and the SH0ES team, and the Digitized Sky Survey

Provided by Nasa/Goddard Space flight center

Hubble Observes Spectacular Supernova Time-Lapse (Astronomy)

The NASA/ESA’s Hubble Space Telescope has tracked the fading light of a supernova in the spiral galaxy NGC 2525, located 70 million light years away. Supernovae like this one can be used as cosmic tape measures, allowing astronomers to calculate the distance to their galaxies. Hubble captured these images as part of one of its major investigations, measuring the expansion rate of the Universe, which can help answer fundamental questions about our Universe’s very nature.

Pictured here is part of the captivating galaxy NGC 2525. Located nearly 70 million light-years from Earth, this galaxy is part of the constellation of Puppis in the southern hemisphere. Together with the Carina and the Vela constellations, it makes up an image of the Argo from ancient greek mythology. On the left, a brilliant supernova is clearly visible in the image. The supernova is formally known as SN2018gv and was first spotted in mid-January 2018. The NASA/ESA Hubble Space Telescope captured the supernova in NGC 2525 as part of one of its major investigations; measuring the expansion rate of the Universe, which can help answer fundamental questions about our Universe’s very nature. Supernovae like this one can be used as cosmic tape measures, allowing astronomers to calculate the distance to their galaxies. ESA/Hubble has now published a unique time-lapse of this galaxy and it’s fading supernova.
CREDIT: ESA/Hubble & NASA, A. Riess and the SH0ES team Acknowledgment: Mahdi Zamani

The supernova, formally known as SN2018gv, was first spotted in mid-January 2018. The NASA/ESA’s Hubble Space Telescope began observing the brilliant brightness of the supernova in February 2018 as part of the research program led by lead researcher and Nobel Laureate Adam Riess of the Space Telescope Science Institute (STScI) and Johns Hopkins University, in Baltimore, USA. The Hubble images center on the barred spiral galaxy NGC 2525, which is located in the constellation of Puppis in the Southern Hemisphere.

The supernova is captured by Hubble in exquisite detail within this galaxy in the left portion of the image. It appears as a very bright star located on the outer edge of one of its beautiful swirling spiral arms. This new and unique time-lapse of Hubble images created by the ESA/Hubble team shows the once bright supernova initially outshining the brightest stars in the galaxy, before fading into obscurity during the year of observations. This time-lapse consists of observations taken over the course of one year, from February 2018 to February 2019.

“No Earthly fireworks display can compete with this supernova, captured in its fading glory by the Hubble Space Telescope,” shared Riess of this new time-lapse of the supernova explosion in NGC 2525.

Supernovae are powerful explosions which mark the end of a star’s life. The type of supernova seen in these images, known as a Type Ia supernova, originate from a white dwarf in a close binary system accreting material from its companion star. If the white dwarf reaches a critical mass (1.44 times the mass of our Sun), its core becomes hot enough to ignite carbon fusion, triggering a thermonuclear runaway process that fuses large amounts of oxygen and carbon together in a matter of seconds. The energy released tears the star apart in a violent explosion, ejecting matter at speeds up to 6% the speed of light and emitting huge amounts of radiation. Type Ia supernovae consistently reach a peak brightness of 5 billion times brighter than our Sun before fading over time.

Because supernovae of this type produce this fixed brightness, they are useful tools for astronomers, known as ‘standard candles’, which act as cosmic tape measures. Knowing the actual brightness of the supernova and observing its apparent brightness in the sky, astronomers can calculate the distance to these grand spectacles and therefore their galaxies. Riess and his team combined the distance measurements from the supernovae with distances calculated using variable stars known as Cepheid variables. Cepheid variables pulsate in size, causing periodic changes in brightness. As this period is directly related to the star’s brightness, astronomers can calculate the distance to them: allowing them to act as another standard candle in the cosmic distance ladder.

Riess and his team are interested in accurately measuring the distance to these galaxies since it helps them better constrain the expansion rate of the Universe, known as the Hubble constant. This value accounts for how fast the Universe is expanding depending on its distance from us, with more distant galaxies moving faster away from us. Since it launched, NASA/ESA’s Hubble Space Telescope has helped dramatically improve the precision of the Hubble constant. Results from the same observing program led by Riess have now reduced the uncertainty of their measurement of the Hubble constant to an unprecedented 1.9%. Further measurements of NGC 2525 will contribute to their goal of reducing the uncertainty down to 1%, pinpointing how fast the Universe is expanding. A more accurate Hubble constant may uncover clues about the invisible dark matter and mysterious dark energy, responsible for accelerating the Universe’s rate of expansion. Together this information can help us understand the history and future fate of our Universe.

A supermassive black hole is also known to be lurking at the centre of NGC 2525. Nearly every galaxy contains a supermassive black hole, which can range in mass from hundreds of thousands to billions of times the mass of the Sun.

Provided by ESA/Hubble Information Center

Einstein’s Theory Of General Relativity Just Got 500 Times Harder To Beat Thanks To The First-Ever Black Hole To Be Caught On Camera (Astronomy)

Albert Einstein’s theory of general relativity proposes that gravity is about matter warping space-time, and it’s stood the test of time for over a century. And, now, observations of the first-ever supermassive black hole to be caught on camera have made it 500 times harder to disprove.

Simulation of M87 black hole showing the motion of plasma as it swirls around the black hole. The bright thin ring that can be seen in blue is the edge of what we call the black hole shadow.University of Arizona

The Event Horizon Telescope’s (EHT) most recent study of the black hole at the center of M87— around 54 million light-years from Earth and 6.5 billion times bigger than our Sun — observed the black hole’s shadow between 2009 to 2017. And it shows that even though it did not change in size, it was a little wobbly.

“Using the gauge we developed, we showed that the measured size of the black hole shadow in M87 tightens the wiggle room for modifications to Einstein’s theory of general relativity by almost a factor of 500 compared to previous tests in the solar system,” explained Feryal Özel, a senior member of the EHT collaboration.

“Many ways to modify general relativity fail at this new and tighter black hole shadow test,” he added.

Einstein’s theory of general relativity survives the extreme

The intense gravity of a black hole curves spacetime, acting like a magnifying glass and causing the black hole shadow to appear larger.

Visualization of the new gauge developed to test the predictions of modified gravity theories against the measurement of the size of the M87 shadow. University of Arizona

The measurement of that visual distortion showed the researchers that the size of the black hole shadow corroborates the predictions of general relativity — a metric theory of gravitation.

According to Einstein, gravity corresponds to changes in the properties of space and time, which in turn changes the straightest-possible paths that objects will naturally follow. Basically, the ‘curvature’ of spacetime is directly related to the energy and momentum of whatever matter and radiation are present.

The supermassive black hole’s ‘wobbly’ shadow proves that Einstein’s theory remains intact even under the most extreme circumstances — a test of gravity along the edge of a supermassive black hole where it’s known to be the strongest.

Black holes exhibit the strongest gravity. University of Arizona

Is there more to a black hole?

The nearly circular shape of the black hole shadow may also lead to a test of the general relativistic no-hair theorem. It states that a black hole is described entirely by its mass, spin, and electrical charge.

This will mean that if two black holes possess the same mass, spin, and electrical charge — they would be considered indistinguishable akin to the identical nature of subatomic particles.

On the other hand, if geometric irregularities are detected, it would potentially indicate the properties that define a black hole extend beyond just its mass, spin, and electrical charge.

“This test will be even more powerful once we image the black hole in the center of our own galaxy and in future EHT observations with additional telescopes that are being added to the array,” said Özel.

Provided by University Of Arizona