SPACE
New image from James Webb Space Telescope reveals astonishing Saturn and its rings
Get ready to be amazed by the latest James Webb Space Telescope (JWST) image.
Reports and ProceedingsIMAGE: IMAGE OF SATURN AND SOME OF ITS MOONS, CAPTURED BY THE JAMES WEBB SPACE TELESCOPE’S NIRCAM INSTRUMENT ON JUNE 25, 2023. IN THIS MONOCHROME IMAGE, NIRCAM FILTER F323N (3.23 MICRONS) WAS COLOR MAPPED WITH AN ORANGE HUE. view more
CREDIT: CREDITS: NASA, ESA, CSA, STSCI, M. TISCARENO (SETI INSTITUTE), M. HEDMAN (UNIVERSITY OF IDAHO), M. EL MOUTAMID (CORNELL UNIVERSITY), M. SHOWALTER (SETI INSTITUTE), L. FLETCHER (UNIVERSITY OF LEICESTER), H. HAMMEL (AURA); IMAGE PROCESSING BY J. DEPASQUALE (STSCI).
New Image from James Webb Space Telescope Reveals Astonishing Saturn and its Rings
June 30, 2023, Mountain View, CA – Get ready to be amazed by the latest James Webb Space Telescope (JWST) image. Saturn’s iconic rings seem to glow eerily in this incredible infrared picture, which also unveils unexpected features in Saturn’s atmosphere.
This image serves as context for an observing program that will test the telescope’s capacity to detect faint moons around the planet and its bright rings. Any newly discovered moons could help scientists put together a more complete picture of the current system of Saturn, as well as its past.
Methane gas absorbs almost all the sunlight falling on the atmosphere at this picture’s specific infrared wavelength (3.23 microns). As a result, Saturn’s familiar striped patterns aren’t visible because the methane-rich upper atmosphere blocks our view of the primary clouds. Instead, Saturn’s disk appears dark, and we see features associated with high-altitude stratospheric aerosols, including large, dark, and diffuse structures in Saturn’s northern hemisphere that don’t align with the planet’s lines of latitude. Interestingly, researchers previously spotted similar wave-like in early JWST NIRCam observations of Jupiter.
Unlike the atmosphere, Saturn’s rings lack methane, so at this infrared wavelength, they are no darker than usual and thus easily outshine the darkened planet. This new image of Saturn also reveals intricate details within the ring system, showcasing several of the planet’s moons like Dione, Enceladus, and Tethys.
“We are very pleased to see JWST produce this beautiful image, which is confirmation that our deeper scientific data also turned out well,” said Dr. Matthew Tiscareno, a senior research scientist at the SETI Institute who led the process of designing this observation. “We look forward to digging into the deep exposures to see what discoveries may await.”
Over the past few decades, missions like NASA’s Pioneer 11, Voyagers 1 and 2, the Cassini spacecraft and the Hubble Space Telescope have observed Saturn’s atmosphere and rings. The image captured by JWST is just a taste of what this observatory will uncover about Saturn in the coming years as scientists. This image is part of a suite of deeply exposed images where researchers hope to identify new ring structures and perhaps even new moons of Saturn.
Moving from the inner to the outer features of Saturn’s rings, we can observe the dark C ring, the bright B ring, the narrow and dark Cassini Division, and the medium-bright A ring with the dark Encke Gap near its outer edge. Additionally, off the outer edge of the A ring, we can see the narrow strand known as the F ring. The rings cast a shadow on the planet and vice versa, creating intriguing visual effects.
In-depth exposures not shown in this image will allow scientists to investigate Saturn’s fainter rings, including the thin G ring and diffuse E ring, which are not visible here. Saturn’s rings consist of an assortment of rocky and icy fragments, ranging in size from smaller than a grain of sand to as large as mountains on Earth. Recently, researchers used JWST to explore Enceladus and discovered a substantial plume emanating from the moon’s southern pole. This plume contains particles and copious amounts of water vapor, contributing to Saturn’s E ring.
Comparing the northern and southern poles of Saturn in this image, we can observe typical
seasonal changes. It’s currently summertime in Saturn’s northern hemisphere, while the southern hemisphere emerges from winter darkness. However, the northern pole appears unusually dark, potentially due to an unknown seasonal process affecting polar aerosols. A faint brightening at the edge of Saturn’s disk might be attributed to high-altitude methane fluorescence or emission from the ionosphere’s trihydrogen ion (H3+). Spectroscopy from JWST could help confirm these possibilities.
Science Credits
NASA, ESA, CSA, STScI, Matt Tiscareno (SETI Institute), Matt Hedman (University of Idaho), Maryame El Moutamid (Cornell University), Mark Showalter (SETI Institute), Leigh Fletcher (University of Leicester), Heidi Hammel (AURA)
Image Processing Credits
J. DePasquale (STScI)
About the Authors
Heidi B. Hammel is a JWST interdisciplinary scientist leading JWST’s Cycle 1 Guaranteed Time Observations (GTO) of the solar system. She is the vice president for science at the Association of Universities for Research in Astronomy (AURA) in Washington, D.C.
Leigh Fletcher is a professor of planetary science at the University of Leicester in England. Leigh is the principal investigator for several of JWST’s Guaranteed Time Observation Programs, including Program 1247 highlighted here.
Matt Tiscareno is a Senior Research Scientist at the SETI Institute, California, where he studies the dynamics of planetary systems, including planetary rings. He is an integral member of the JWST Guaranteed Time Observation team for the study of Saturn.
About the SETI Institute
Founded in 1984, the SETI Institute is a non-profit, multi-disciplinary research and education organization whose mission is to lead humanity’s quest to understand the origins and prevalence of life and intelligence in the Universe and to share that knowledge with the world. Its research encompasses the physical and biological sciences and leverages expertise in data analytics, machine learning and advanced signal detection technologies. The SETI Institute is a distinguished research partner for industry, academia and government agencies, including NASA and NSF.
NASA’s Webb identifies the earliest strands of the cosmic web
IMAGE: THIS DEEP GALAXY FIELD FROM WEBB’S NIRCAM (NEAR-INFRARED CAMERA) SHOWS AN ARRANGEMENT OF 10 DISTANT GALAXIES MARKED BY EIGHT WHITE CIRCLES IN A DIAGONAL, THREAD-LIKE LINE. (TWO OF THE CIRCLES CONTAIN MORE THAN ONE GALAXY.) THIS 3 MILLION LIGHT-YEAR-LONG FILAMENT IS ANCHORED BY A VERY DISTANT AND LUMINOUS QUASAR – A GALAXY WITH AN ACTIVE, SUPERMASSIVE BLACK HOLE AT ITS CORE. THE QUASAR, CALLED J0305-3150, APPEARS IN THE MIDDLE OF THE CLUSTER OF THREE CIRCLES ON THE RIGHT SIDE OF THE IMAGE. ITS BRIGHTNESS OUTSHINES ITS HOST GALAXY. THE 10 MARKED GALAXIES EXISTED JUST 830 MILLION YEARS AFTER THE BIG BANG. THE TEAM BELIEVES THE FILAMENT WILL EVENTUALLY EVOLVE INTO A MASSIVE CLUSTER OF GALAXIES. view more
CREDIT: CREDITS: NASA, ESA, CSA, FEIGE WANG (UNIVERSITY OF ARIZONA), AND JOSEPH DEPASQUALE (STSCI)
Galaxies are not scattered randomly across the universe. They gather together not only into clusters, but into vast interconnected filamentary structures with gigantic barren voids in between. This “cosmic web” started out tenuous and became more distinct over time as gravity drew matter together.
Astronomers using NASA’s James Webb Space Telescope have discovered a thread-like arrangement of 10 galaxies that existed just 830 million years after the big bang. The 3 million light-year-long structure is anchored by a luminous quasar – a galaxy with an active, supermassive black hole at its core. The team believes the filament will eventually evolve into a massive cluster of galaxies, much like the well-known Coma Cluster in the nearby universe.
“I was surprised by how long and how narrow this filament is,” said team member Xiaohui Fan of the University of Arizona in Tucson. “I expected to find something, but I didn't expect such a long, distinctly thin structure.”
“This is one of the earliest filamentary structures that people have ever found associated with a distant quasar,” added Feige Wang of the University of Arizona in Tucson, the principal investigator of this program.
This discovery is from the ASPIRE project (A SPectroscopic survey of biased halos In the Reionization Era), whose main goal is to study the cosmic environments of the earliest black holes. In total, the program will observe 25 quasars that existed within the first billion years after the big bang, a time known as the Epoch of Reionization.
“The last two decades of cosmology research have given us a robust understanding of how the cosmic web forms and evolves. ASPIRE aims to understand how to incorporate the emergence of the earliest massive black holes into our current story of the formation of cosmic structure,” explained team member Joseph Hennawi of the University of California, Santa Barbara.
Growing Monsters
Another part of the study investigates the properties of eight quasars in the young universe. The team confirmed that their central black holes, which existed less than a billion years after the big bang, range in mass from 600 million to 2 billion times the mass of our Sun. Astronomers continue seeking evidence to explain how these black holes could grow so large so fast.
“To form these supermassive black holes in such a short time, two criteria must be satisfied. First, you need to start growing from a massive ‘seed’ black hole. Second, even if this seed starts with a mass equivalent to a thousand Suns, it still needs to accrete a million times more matter at the maximum possible rate for its entire lifetime,” explained Wang.
“These unprecedented observations are providing important clues about how black holes are assembled. We have learned that these black holes are situated in massive young galaxies that provide the reservoir of fuel for their growth,” said Jinyi Yang of the University of Arizona, who is leading the study of black holes with ASPIRE.
Webb also provided the best evidence yet of how early supermassive black holes potentially regulate the formation of stars in their galaxies. While supermassive black holes accrete matter, they also can power tremendous outflows of material. These winds can extend far beyond the black hole itself, on a galactic scale, and can have a significant impact on the formation of stars.
“Strong winds from black holes can suppress the formation of stars in the host galaxy. Such winds have been observed in the nearby universe but have never been directly observed in the Epoch of Reionization,” said Yang. “The scale of the wind is related to the structure of the quasar. In the Webb observations, we are seeing that such winds existed in the early universe.”
These results were published in two papers in The Astrophysical Journal Letters on June 29.
The James Webb Space Telescope is the world's premier space science observatory. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency), and CSA (Canadian Space Agency).
JOURNAL
The Astrophysical Journal
ARTICLE PUBLICATION DATE
29-Jun-2023
Space debris: a quantitative analysis of the in-orbit collision risk and its effects on the earth
The model developed by researchers at the Faculty of Economics of the UMA establishes the optimal rate of satellite launches to maximize benefits
Peer-Reviewed PublicationVIDEO: THE MODEL DEVELOPED BY RESEARCHERS AT THE FACULTY OF ECONOMICS OF THE UMA ESTABLISHES THE OPTIMAL RATE OF SATELLITE LAUNCHES TO MAXIMIZE BENEFITS view more
CREDIT: UNIVERSITY OF MALAGA
The amount of space debris has not stopped increasing since the first satellite was launched in 1957. The European Space Agency (ESA) estimates that there are more than 131,000,000 useless space waste objects, between 1 millimeter and 10 centimeters, currently orbiting around the Earth at an average speed of 36,000 kilometers per hour, which come from different sources such as last stages of rockets, satellites that are no longer operational, and even tools lost in space by astronauts.
“Any piece larger than 1 centimeter is potentially lethal in case of collision”, says the Professor at the University of Malaga José Luis Torres, who, together with Professor Anelí Bongers, has coordinated a project on Space Economy that establishes, from a quantitative point of view, a theoretical model that determines the rate of satellite launches that is optimal to maximize benefits based on the amount of space debris.
Particularly, using data from the NASA and the ESA, the developed model is based on computational simulations that analyze the effects of anti-satellite tests on the amount of space debris and the probability of collision with operational satellites –there are currently around 6,000 satellites in orbit.
This way, the model proposed by these researchers at the UMA, which has been published in the scientific journal Defense and Peace Economics, dynamically determines the amount of space debris based on the optimal behavior of companies operating in space when establishing the rate of launches and the number of satellites.
According to these experts, the number of launches and satellites is negatively affected by the amount of space debris. “The calculations also show that anti-satellite tests generate more than 102,000 new pieces of this waste larger than 1 centimeter and that its negative effects take 1,000 years to disappear due to the high altitude at which tests are carried out”, they assure.
Market failure
The researchers at the UMA have studied the space from an economic point of view, since, as they say, it is a global common good that, as with the high seas, “will end up being overexploited”. Moreover, since there is no express regulation, except for a non-binding International Treaty of the United Nations, it is an example of “market failure”, because due to the absence of property rights, there is a tendency to misuse this resource and, therefore, generate 'negative externalities'.
Likewise, they warn that, as we are increasingly dependent on the companies operating in space, especially tech companies, the volume of space debris will continue rising and so will the likelihood of collision.
“We are facing with a huge unregulated market, which problems have just started”, underline the researchers at the UMA.
Star Wars: a war in space
Finally, the study quantifies the effects of a hypothetic war in space that simulates the destruction of 250 satellites. Using this model proposed by the UMA, it is estimated that space debris would rise by 25,500,000 fragments larger than 1 centimeter, thus increasing the probability of collision and the number of destroyed satellites.
The objective is to warn of the effects of space debris on the global economy and the potential physical problems that it may cause on the Earth, as well as on the human use of space, which, as they warn on the basis of this simulation, will disappear for both commercial and scientific activities if the current rate of space debris generation continues.
The model developed by researchers at the Faculty of Economics of the UMA establishes the optimal rate of satellite launches to maximize benefits
The Professor at the University of Malaga José Luis Torres, who, together with Professor Anelí Bongers, have coordinated a project on Space Economy that establishes, from a quantitative point of view, a theoretical model that determines the rate of satellite launches that is optimal to maximize benefits based on the amount of space debris
CREDIT
University of Malaga
Bibliography:
Bongers, A., Torres, J.L. (2023). Star Wars: Anti-Satellite Weapons and Orbital Debris. Defence and Peace Economics, 1-20. https://doi.org/10.1080/10242694.2023.2208020
JOURNAL
Defence and Peace Economics
METHOD OF RESEARCH
Meta-analysis
SUBJECT OF RESEARCH
People
ARTICLE TITLE
Star Wars: Anti-Satellite Weapons and Orbital Debris
Astrophysicists propose a new way of measuring cosmic expansion: lensed gravitational waves
IMAGE: WHEN TWO BLACK HOLES MERGE, THEY RELEASE GRAVITATIONAL WAVES, THAT WHEN LENSED BY MASSIVE OBJECTS AS THEY TRAVEL TO EARTH, COULD BE USED TO CALCULATE THE RATE OF COSMIC EXPANSION. view more
CREDIT: NASA'S GODDARD SPACE FLIGHT CENTER/SCOTT NOBLE; SIMULATION DATA, D'ASCOLI ET AL. 2018
(Santa Barbara, Calif.) — The universe is expanding; we’ve had evidence of that for about a century. But just how quickly celestial objects are receding from each other is still up for debate.
It’s no small feat to measure the rate at which objects move away from each other across vast distances. Since the discovery of cosmic expansion, its rate has been measured and re-measured with increasing precision, with some of the latest values ranging from 67.4 up to 76.5 kilometers per second per megaparsec, which relates the recession velocity (in kilometers per second) to the distance (in megaparsecs).
The discrepancy between different measurements of cosmic expansion is called the “Hubble tension.” Some have called it a crisis in cosmology. But for UC Santa Barbara theoretical astrophysicist Tejaswi Venumadhav Nerella and colleagues at the Tata Institute of Fundamental Research in Bangalore, India, and the Inter-University Center for Astronomy and Astrophysics in Pune, India, it is an exciting time.
Since the first detection of gravitational waves in 2015, detectors have been significantly improved and are poised to yield a rich haul of signals in the coming years. Nerella and his colleagues have come up with a method to use these signals to measure the universe’s expansion, and perhaps help to settle the debate once and for all. “A major scientific goal of future detectors is to deliver a comprehensive catalog of gravitational wave events, and this will be a completely novel use of the remarkable dataset,” said Nerella, co-author of a paper published in Physical Review Letters.
Measurements of the cosmic expansion rate boil down to velocity and distance. Astronomers use two kinds of methods to measure distances: the first start with objects with a known length (“standard rulers”) and look at how big they appear in the sky. These "objects" are features in cosmic background radiation, or in the distribution of galaxies in the universe.
A second class of methods starts with objects of known luminosity (“standard candles”) and measures their distances from Earth using their apparent brightness. These distances are connected to those of farther bright objects and so on, which builds up a chain of measurement schemes that is often called the “cosmic distance ladder.” Incidentally, gravitational waves themselves can also help measure cosmic expansion, since the energy released by the collision of neutron stars or black holes can be used to estimate the distance to these objects.
The method that Nerella and his co-authors propose belongs to the second class but uses gravitational lensing. This is a phenomenon that occurs when massive objects warp spacetime, and bend waves of all kinds that travel near the objects. In rare cases, lensing can produce multiple copies of the same gravitational wave signal that reach Earth at different times — the delays between the signals for a population of multiple imaged events can be used to calculate the universe’s expansion rate, according to the researchers.
“We understand very well just how sensitive gravitational wave detectors are, and there are no astrophysical sources of confusion, so we can properly account for what gets into our catalog of events,” Nerella said. “The new method has sources of error that are complementary to those of existing methods, which makes it a good discriminator.”
The sources of these signals would be binary black holes: systems of two black holes that orbit each other and ultimately merge, releasing massive amounts of energy in the form of gravitational waves. We haven’t yet detected strongly lensed examples of these signals, but the upcoming generation of ground-based detectors is expected to have the necessary level of sensitivity.
“We expect the first observation of lensed gravitational waves in the next few years,” said study co-author Parameswaran Ajith. Additionally, these future detectors should be able to see farther into space and detect weaker signals.
The authors expect these advanced detectors to start their search for merging black holes in the next decade. They anticipate recording signals from a few million black hole pairs, a small fraction (about 10,000) of which will appear multiple times in the same detector due to gravitational lensing. The distribution of the delays between these repeat appearances encodes the Hubble expansion rate.
According to lead author Souvik Jana, unlike other methods of measurement, this method does not rely on knowing the exact locations of, or the distances to, these binary black holes. The only requirement is to accurately identify a sufficiently large number of these lensed signals. The researchers add that observations of lensed gravitational waves can even provide clues on other cosmological questions, such as the nature of the invisible dark matter that makes up much of the energy content of the universe.
JOURNAL
Physical Review Letters
ARTICLE TITLE
Cosmography Using Strongly Lensed Gravitational Waves from Binary Black Holes
Unveiling the origins of merging black holes in galaxies like our own
Harnessing advanced simulation tools, a team of scientists from UNIGE, Northwestern University and University of Florida shed light on the enigmatic nature of these celestial "beasts".
Peer-Reviewed PublicationIMAGE: A 31.5 SOLAR-MASS BLACK HOLE WITH AN 8.38 SOLAR-MASS BLACK HOLE COMPANION VIEWED IN FRONT OF ITS (COMPUTER GENERATED) STELLAR NURSERY PRIOR TO MERGING. view more
CREDIT: © AARON M. GELLER / NORTHWESTERN CIERA & NUIT-RCS; ESO / S. BRUNIER
Black holes, some of the most captivating entities in the cosmos, possess an immense gravitational pull so strong that not even light can escape. The groundbreaking detection of gravitational waves in 2015, caused by the coalescence of two black holes, opened a new window into the universe. Since then, dozens of such observations have sparked the quest among astrophysicists to understand their astrophysical origins. Thanks to the POSYDON code’s recent major advancements in simulating binary-star populations, a team of scientists, including some from the University of Geneva (UNIGE), Northwestern University and the University of Florida (UF) predicted the existence of merging massive, 30 solar mass black hole binaries in Milky Way-like galaxies, challenging previous theories. These results are published in Nature Astronomy.
Stellar-mass black holes are celestial objects born from the collapse of stars with masses of a few to low hundreds of times that of our sun. Their gravitational field is so intense that neither matter nor radiation can evade them, making their detection exceedingly difficult. Therefore, when the tiny ripples in spacetime produced by the merger of two black holes were detected in 2015, by the Laser Interferometer Gravitational-wave Observatory (LIGO), it was hailed as a watershed moment. According to astrophysicists, the two merging black holes at the origin of the signal were about 30 times the mass of the sun and located 1.5 billion light-years away.
Bridging Theory and Observation
What mechanisms produce these black holes? Are they the product of the evolution of two stars, similar to our sun but significantly more massive, evolving within a binary system? Or do they result from black holes in densely populated star clusters running into each other by chance? Or might a more exotic mechanism be involved? All of these questions are still hotly debated today.
The POSYDON collaboration, a team of scientists from institutions including the University of Geneva (UNIGE), Northwestern and the University of Florida (UF) has made significant strides in simulating binary-star populations. This work is helping to provide more accurate answers and reconcile theoretical predictions with observational data. "As it is impossible to directly observe the formation of merging binary black holes, it is necessary to rely on simulations that reproduce their observational properties. We do this by simulating the binary-star systems from their birth to the formation of the binary black hole systems," explains Simone Bavera, a post-doctoral researcher at the Department of Astronomy of the UNIGE’s Faculty of Science and leading author of this study.
Pushing the Limits of Simulation
Interpreting the origins of merging binary black holes, such as those observed in 2015, requires comparing theoretical model predictions with actual observations. The technique used to model these systems is known as "binary population synthesis". "This technique simulates the evolution of tens of millions of binary star systems in order to estimate the statistical properties of the resulting gravitational-wave source population. However, to achieve this in a reasonable time frame, researchers have until now relied on models that use approximate methods to simulate the evolution of the stars and their binary interactions. Hence, the oversimplification of single and binary stellar physics leads to less accurate predictions," explains Anastasios Fragkos, assistant professor in the Department of Astronomy at the UNIGE Faculty of Science.
POSYDON has overcome these limitations. Designed as open-source software, it leverages a pre-computed large library of detailed single- and binary-star simulations to predict the evolution of isolated binary systems. Each of these detailed simulations might take up to 100 CPU hours to run on a supercomputer, making this simulation technique not directly applicable for binary population synthesis. "However, by precomputing a library of simulations that cover the entire parameter space of initial conditions, POSYDON can utilize this extensive dataset along with machine learning methods to predict the complete evolution of binary systems in less than a second. This speed is comparable to that of previous-generation rapid population synthesis codes, but with improved accuracy," explains Jeffrey Andrews, assistant professor in the Department of Physics at UF.
Introducing a New Model
"Models prior to POSYDON predicted a negligible formation rate of merging binary black holes in galaxies similar to the Milky Way, and they particularly did not anticipate the existence of merging black holes as massive as 30 times the mass of our sun. POSYDON has demonstrated that such massive black holes might exist in Milky Way-like galaxies," explains Vicky Kalogera, a Daniel I. Linzer Distinguished University Professor of Physics and Astronomy in the Department of Physics and Astronomy at Northwestern, director of the Center of Interdisciplinary Exploration and Research in Astrophysics (CIERA), and co-author of this study.
Previous models overestimated certain aspects, such as the expansion of massive stars, which impacts their mass loss and the binary interactions. These elements are key ingredients that determine the properties of merging black holes. Thanks to fully self-consistent detailed stellar-structure and binary-interaction simulations, POSYDON achieves more accurate predictions of merging binary black hole properties such as their masses and spins.
This study is the first to utilize the newly released open-source POSYDON software to investigate merging binary black holes. It provides new insights into the formation mechanisms of merging black holes in galaxies like our own. The research team is currently developing a new version of POSYDON, which will include a larger library of detailed stellar and binary simulations, capable of simulating binaries in a wider range of galaxy types.
JOURNAL
Nature Astronomy
METHOD OF RESEARCH
News article
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
The formation of merging black holes with masses beyond 30 M⊙ at solar metallicity
ARTICLE PUBLICATION DATE
29-Jun-2023
WVU faculty, students contribute to cosmic breakthrough uncovering evidence of low-frequency gravitational waves
IMAGE: RESEARCHERS AT WEST VIRGINIA UNIVERSITY — WORKING AS PART OF THE NORTH AMERICAN NANOHERTZ OBSERVATORY FOR GRAVITATIONAL WAVES, OR NANOGRAV, COLLABORATION — UTILIZED THE GREEN BANK TELESCOPE IN POCAHONTAS COUNTY TO HELP UNCOVER EVIDENCE OF LOW-FREQUENCY GRAVITATIONAL WAVES FOR THE FIRST TIME. view more
CREDIT: SUBMITTED PHOTO/JAY YOUNG, GREEN BANK OBSERVATORY
More than two dozen researchers with ties to West Virginia University have helped unearth evidence of ripples in spacetime that have never been observed before now.
Gravitational waves travel outwards from a source at light speed, stretching and squeezing the very fabric of spacetime — for instance, making the length of a ruler longer or shorter, or making time tick a little faster or slower as the wave passes. The first evidence for these ripples at very low frequencies was identified by a cohort of nearly 200 scientists from the United States and Canada. These low-frequency oscillations happen with periods of years to decades and were recognized through high-precision timing of cosmic radio clocks called pulsars.
This result emerged from 15 years of data acquired by the North American Nanohertz Observatory for Gravitational Waves, or NANOGrav, which includes many researchers from the WVU Department of Physics and Astronomy and the Center for Gravitational Waves and Cosmology.
Of the 95 authors documenting this evidence in newly published papers, 30 are associated with WVU, including 11 authors currently at the University and 19 from past years, generally those trained as undergraduate students, graduate students or postdoctoral researchers.
Maura McLaughlin, Eberly Distinguished Professor in the Department of Physics and Astronomy, and director of the Center for Gravitational Waves and Cosmology, was a founding member of the NANOGrav collaboration and serves as co-director of the NANOGrav Physics Frontier Center. She is also a member of the international team of scientists collaborating globally on the International Pulsar Timing Array project.
“NANOGrav and its international partners have discovered the first evidence for a background hum of gravitational waves,” McLaughlin said. “The universe is not static and never changing — we are awash in a space that is constantly stretching and squeezing.”
A series of papers on NANOGrav’s findings and observations has been published in The Astrophysical Journal Letters.
“The papers describe the evidence as arising from a ‘gravitational wave background,’ which refers to the indiscernible signals coming from many sources of gravitational waves in the universe,” said Sarah Burke-Spolaor, assistant professor at WVU, who founded NANOGrav’s Astrophysics Working Group in 2011.
“This can be understood by thinking about a huge orchestra tuning up their instruments: you know it’s an orchestra, and know there are many instruments, but can’t necessarily make one out specifically. We don’t yet know what is giving rise to this signal, but our publications discuss several possibilities: supermassive black holes in galaxy mergers, cosmic strings and relic echoes of the big bang.”
One popular theory is that pairs of supermassive black holes orbiting one another could be the dominant source of these low-frequency gravitational waves. The black holes are estimated to be billions of times the mass of the sun.
Supermassive black holes are believed to reside at the centers of the largest galaxies in the universe, although they have never been directly detected. When two galaxies merge, black holes from each wind up sinking to the center of the newly combined galaxy, orbiting each other as a binary system. Ultimately, the two black holes also merge. In the meantime, they stretch and squeeze the fabric of spacetime, generating gravitational waves that propagate away from their origin galaxy like ripples in a pond.
This isn’t the first gravitational wave breakthrough involving WVU. Sean McWilliams, associate professor of physics and astronomy, was part of the team in 2015 that detected gravitational waves for the first time, confirming Albert Einstein’s general theory of relativity. That finding was made possible by Laser Interferometer Gravitational-Wave Observatory, or LIGO, detectors.
But unlike the fleeting high-frequency gravitational waves seen by ground-based instruments like LIGO, the low-frequency signal observed by NANOGrav could be perceived only with a detector much larger than the Earth. To meet that need, astronomers turned a sector of the Milky Way galaxy into a gravitational wave antenna by making use of pulsars, the ultra-dense remnants of a star’s core following a supernova explosion. When observed from Earth, pulsars appear to “pulse,” making them useful as precise cosmic timepieces. NANOGrav’s effort collected data from 68 pulsars to form a type of detector called a pulsar timing array.
“Gravitational waves were not directly detected until LIGO,” said Emmanuel Fonseca, assistant professor of astronomy and NANOGrav member who was involved in the new discovery. “But it could only observe gravitational waves within a certain part of the spectrum, like seeing gravitational wave versions of optical light when there are gravitational wave versions of X-rays. What NANOGrav did was confirm the existence of gravitational waves at a completely different part of the spectrum.”
The team relied heavily on the Green Bank Telescope located in Pocahontas County — the world’s largest fully steerable radio telescope — for observation and data collection. The Arecibo Observatory in Puerto Rico and the Very Large Array in New Mexico were also utilized.
“Pulsars are actually very faint radio sources, so we require thousands of hours a year on the world’s largest telescopes to carry out this experiment,” McLaughlin said. “These results are made possible through the National Science Foundation’s continued commitment to these exceptionally sensitive radio observatories.”
Burke-Spolaor said this newest discovery is a testament to the University’s expertise and dedication to the space sciences.
“WVU is one of maybe two or three universities that serve as a major hub for all branches of science contributing to NANOGrav as a galaxy-sized detector that is beginning to detect the gravitational universe,” she said. “NANOGrav involves a unique detector — essentially using pulsars as a GPS system — and requires extensive work by experts on stellar evolution, gravity, fundamental physics, galaxy evolution and black holes. We have contributors at WVU who span that range. The University’s close involvement with Green Bank Telescope has contributed a strong West Virginia-based network of scientists.”
Burke-Spolaor also applauded the skill and dedication of University students and postdoctoral researchers who contributed to the project.
Graduate student Andrew Kaiser, of Fayetteville, Arkansas, has spent much of his research experience exploring and characterizing sources of noise and signals in gravitational wave detectors. For this discovery, Kaiser conducted statistical analyses included in the published papers.
“I analyzed specific pulsars by looking at noise and timing in a very myopic way,” he said. “With that information, we can combine it with the statistics we use in our detections.”
After graduating with a bachelor’s degree from the University of Arkansas, Kaiser wound up at WVU because of its opportunities in the field of gravitational waves.
“There were really big exciting things happening in pulsar timing,” he said. “Coming to WVU to witness the triumphs of pulsar timing firsthand has been one of the biggest things for me.”
“Since coming here and joining NANOGrav, I’ve spent a lot of time thinking about using gravitational waves and multi-messenger observations to search for and study sources,” said Tingting Liu, a postdoctoral researcher originally from Nanjing, China.
Liu explained that light is a messenger of astrophysical information, while gravitational waves are another messenger. When two or more messengers combine, that produces multi-messenger observations.
The team said future studies will enable scientists to view gravitational waves through a new window along with how the universe evolved on the largest scales, providing information about how often galaxies collide and what drives black holes to merge.
Researchers also said they believe gravitational ripples of the Big Bang itself may make up a fraction of this new evidence, offering insight into how the universe was formed.ITY
An artist's interpretation shows an array of pulsars being affected by gravitational ripples produced by a supermassive black hole binary in a distant galaxy.
CREDIT
Submitted Illustration/Aurore Simonnet, NANOGrav Collaboration
JOURNAL
The Astrophysical Journal Letters
ARTICLE TITLE
The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background
ARTICLE PUBLICATION DATE
29-Jun-2023
A simulation finds solutions to a central mystery in space physics
How are plasma eruptions in near-Earth space formed? Vlasiator, a model designed at the University of Helsinki for simulating near-Earth space, demonstrated that the two central theories on the occurrence of eruptions are simultaneously valid
Peer-Reviewed PublicationIMAGE: PLASMA ERUPTIONS IN NEAR-EARTH SPACE view more
CREDIT: JANI NÄRHI
How are plasma eruptions in near-Earth space formed? Vlasiator, a model designed at the University of Helsinki for simulating near-Earth space, demonstrated that the two central theories on the occurrence of eruptions are simultaneously valid: eruptions are explained by both magnetic reconnection and kinetic instabilities.
Rapid plasma eruptions known as plasmoids take place on the nightside of the magnetosphere. Plasmoids are also associated with the sudden brightening of the aurora. The space physics research group at the University of Helsinki investigates and simulates these difficult-to-predict eruptions in near-Earth space using the Vlasiator model.
“The phenomena associated with plasmoids cause the most intense but the least predictable magnetic disturbances, which can cause, for example, disturbances in electrical grids,” says Professor of Computational Space Physics Minna Palmroth from the University of Helsinki.
“These eruptions occur on a daily basis, in varying sizes, in the ‘tail’ of the magnetosphere.”
Palmroth, who was recently awarded the Copernicus Medal, is also the director of the Centre of Excellence in Research of Sustainable Space, and the principal investigator for the Vlasiator simulation.
“The chain of events leading to plasmoids is one of the longest-standing unresolved questions in space physics: solutions have been sought for it since the 1960s,” Palmroth says.
Near-Earth space is a unique place for understanding plasma eruptions
Two competing lines of thinking have been proposed to explain the course of events, the first asserting that magnetic reconnection severs a part of the magnetotail into a plasmoid. According to the other explanation, kinetic instabilities disrupt the current sheet (a wide, thin distribution of electric current) maintaining the tail, which eventually results in the ejection of a plasmoid. Arguments about the primacy of these two phenomena have been ongoing for decades.
“It now appears that the causalities are in fact more complex than previously understood,” Palmroth says.
The Vlasiator simulation, which requires the processing power of a supercomputer, modelled near-Earth space for the first time in six dimensions and on a scale corresponding to the size of the magnetosphere. The 6D modelling was successful in describing the physics phenomena underlying both paradigms.
“It was a difficult technical challenge that no one else has been able to model,” Palmroth says. Behind the achievement is more than 10 years of software development.
Consequently, the study was able to demonstrate that both magnetic reconnection and kinetic instabilities explain the functioning of the magnetotail. The phenomena associated with these seemingly contradictory theories actually both take place, and simultaneously.
The finding helps to understand how plasma eruptions can occur. This helps in designing spacecraft and equipment, observing these events for further research, and improving the predictability of space weather by improving the understanding of near-Earth space.
The findings were published in the distinguished Nature Geoscience journal.
JOURNAL
Nature Geoscience
METHOD OF RESEARCH
Computational simulation/modeling
ARTICLE PUBLICATION DATE
29-Jun-2023
To the Moon and back: Australia-first communications network paves the way for high-speed data in space
West Australian researchers are set to build a next-generation communications network that can send high-speed data to and from objects in space
Grant and Award AnnouncementVIDEO: ASSOCIATE PROFESSOR SASCHA SCHEDIWY, FROM THE UNIVERSITY OF WESTERN AUSTRALIA NODE OF THE INTERNATIONAL CENTRE FOR RADIO ASTRONOMY RESEARCH (ICRAR), TALKS ABOUT TERANET: A COMMUNICATIONS NETWORK THAT CAN SEND HIGH-SPEED DATA TO AND FROM SPACE. view more
CREDIT: RED EMPIRE MEDIA
The $6.5 million project, which has received a $4.4 million grant from the Australian Space Agency, $500,000 each from the Western Australian Government and The University of Western Australia, will employ a new technology that uses super-fast lasers to talk to satellites and spacecraft.
It’s called ‘free-space optical communications’, and it’s 1000 times faster than the radio communications currently used to communicate in space.
Project leader Associate Professor Sascha Schediwy, from The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR), is a world expert in optical communications.
He said the project—called TeraNet—will be one of the first commercial optical communications networks in Australia.
The network will be capable of providing day-to-day support to missions in space.
Associate Professor Schediwy said the network’s main commercial application will be transferring data to and from satellites orbiting the planet.
But the team also plans to explore high-speed communications in deep space, including to the Moon.
“It’s about supporting all these different customers and space missions in low Earth orbit,” Associate Professor Schediwy said.
“And then also being capable of advanced communications for things like NASA’s Artemis missions to the Moon.”
It means Western Australia could receive transmissions from the first woman and first person of colour to land on the lunar surface.
The network will be made up of two fixed ground stations at UWA and Mingenew, and a third, mobile station initially deployed at New Norcia.
Associate Professor Schediwy said NASA and other space agencies need communication stations worldwide to maintain continuous contact with missions as the Earth rotates.
“Western Australia’s geography and climate means it’s one of the best places in the world to host these ground stations,” he said.
Associate Professor Schediwy’s team, who are affiliated with UWA’s International Space Centre, will build the network with industry partners Goonhilly Australia and Thales Australia
Goonhilly Earth Station chief executive Ian Jones said the company has collaborated with Associate Professor Schediwy and the UWA team for a few years to develop coherent optical ground-to-space communications.
“We are delighted to now see this move to the next exciting phase where we can assist in turning this into a technically mission-ready and commercially-operational service, especially for lunar communication,” he said.
“Goonhilly is the global pioneer in commercialising lunar communications and UWA is the world leader in this technology.
“This is precisely the reason we intend to grow our business in Western Australia and help to develop the lunar economy and the Australian space economy.”
Along with the support from industry partners, Associate Professor Schediwy said the Australian Space Agency funding will allow Australia to develop its own optical communications infrastructure and partner with international space agencies.
“We have this leapfrog opportunity to get there first and develop this sovereign capability,” he said.
“And we can reap the benefits of having Australian industries and Australian researchers involved from day one.”
One of the strongest drivers for increased data rates is the rise of advanced Earth observation and imaging satellites carrying ‘hyperspectral cameras’.
These satellites take high-resolution images of the Earth’s surface used for disaster management and national defence, generating huge amounts of data.
“Currently, the data on some of those satellites need to be compressed or thrown away, because the capacity is not there to downlink all that data,” Associate Professor Schediwy said.
“So by expanding to optical communications, with a ground station network to support them, we’ll be able to use them to their full capability.”
Australian Space Agency head Enrico Palermo said the projects supported by the Agency show some of the many ways space technologies are improving how we live and work.
“By helping Australian organisations to develop their space heritage, they can break into new markets and supply chains and take their innovative Aussie technology to the world,” he said.
“That will help them to grow, keep their ideas in Australia and generate more employment opportunities here.”
The network is due to be completed in 2026.
Scientists use new method to detect most energetic ultraviolet/optical flare ever
Researchers from the Purple Mountain Observatory (PMO) of the Chinese Academy of Sciences and the Italian National Institute for Astrophysics have proposed a new method to measure moderately saturated sources of the Ultra-Violet Optical Telescope onboard the Swift satellite (Swift/UVOT), and identified GRB 220101A as the most energetic ultraviolet/optical flare ever detected.
The study was published in Nature Astronomy on June 26.
Gamma-Ray Bursts (GRBs) are the most violent explosions in the universe. Their prompt radiation is mainly in the soft gamma-ray band and last briefly (i.e., from milliseconds to at most hours). The prompt emission is then followed by the X-ray, optical and radio afterglow emission, which lasts for weeks or even years.
The prompt optical emission of GRB 080319B sets the universe-wide luminosity record for an ultraviolet/optical emission in 2008. It was so bright that an observer in a dark location could see it with the naked eye. The optical flare radiation from GRB 080319B traced the gamma-ray light curve and hence the activity of the central engine. But now, GRB 220101A has broken the earlier record.
On New Year's Day 2022, the Swift satellite detected a new burst, GRB 220101A. The redshift of GRB 220101A was measured at 4.618. At such a high redshift, the observed optical photons were in the ultraviolet band and suffered from very serious absorption. Consequently, the intrinsic radiation flux was about 100 times higher than the observed value. Just 79 seconds after the burst, Swift/UVOT performed a quick 150-second observation in event mode in the White band.
The researchers then conducted high-time-resolution photometric analysis that revealed a rapid evolution of the flux. In particular, at the peak time the UVOT telescope was already moderately saturated.
"We proposed a processing method for UVOT data, based on the telescope's point spread function, and verified that it indeed provides reliable flux measurements," said Prof. FAN Yizhong from PMO, the corresponding author of the study. After the proper distance and absorption corrections, the absolute magnitude of the ultraviolet/optical emission of GRB 220101A reached -39.4, making it the only source to date with an absolute magnitude brighter than -39.
"It is also the first time to detect an extremely energetic ultraviolet/optical flare with a space telescope," Prof. FAN added.
The luminosity of GRB 220101A is approximately 400 quadrillion times that of the Sun, which breaks the 14-year record held by GRB 080319B. It also suggests a new astrophysical process, demonstrating the diversity of physical origins of super-bright optical-ultraviolet bursts.
The China–France Space Variable Objects Monitor (SVOM) satellite, scheduled to launch in early 2024, is expected to be able to detect extremely energetic ultraviolet/optical flares at even higher redshifts.
JOURNAL
Nature Astronomy
ARTICLE TITLE
An optical–ultraviolet flare with absolute AB magnitude of −39.4 detected in GRB 220101A
ARTICLE PUBLICATION DATE
26-Jun-2023
