From Pennsylvania State University: “Excess neutrinos and missing gamma rays?”

From Pennsylvania State University

June 30, 2020
Sam Sholtis

Coronae of supermassive black holes may be the hidden sources of mysterious cosmic neutrinos seen on Earth.

NASA Hubble Space Telescope image of Galaxy NGC 1068 with its active black hole shown as an illustration in the zoomed-in inset. A new model suggests that the corona around such supermassive black holes could be the source of high-energy cosmic neutrinos observed by the IceCube Neutrino Observatory. Image: NASA/JPL-Caltech

The origin of high-energy cosmic neutrinos observed by the IceCube Neutrino Observatory, whose detector is buried deep in the Antarctic ice, is an enigma that has perplexed physicists and astronomers.

U Wisconsin ICECUBE neutrino detector at the South Pole

A new model could help explain the unexpectedly large flux of some of these neutrinos inferred by recent neutrino and gamma-ray data. A paper by Penn State researchers describing the model, which points to the supermassive black holes found at the cores of active galaxies as the sources of these mysterious neutrinos, appears June 30 in the journal Physical Review Letters.

“Neutrinos are subatomic particles so tiny that their mass is nearly zero and they rarely interact with other matter,” said Kohta Murase, assistant professor of physics and of astronomy and astrophysics at Penn State and a member of Center for Multimessenger Astrophysics in the Institute for Gravitation and the Cosmos (IGC), who led the research. “High-energy cosmic neutrinos are created by energetic cosmic-ray accelerators in the universe, which may be extreme astrophysical objects such as black holes and neutron stars. They must be accompanied by gamma rays or electromagnetic waves at lower energies, and even sometimes gravitational waves. So, we expect the levels of these various ‘cosmic messengers’ that we observe to be related. Interestingly, the IceCube data have indicated an excess emission of neutrinos with energies below 100 teraelectron volt (TeV), compared to the level of corresponding high-energy gamma rays seen by the Fermi Gamma-ray Space Telescope.”

NASA/Fermi Gamma Ray Space Telescope

Scientists combine information from all of these cosmic messengers to learn about events in the universe and to reconstruct its evolution in the burgeoning field of “multimessenger astrophysics.” For extreme cosmic events, like massive stellar explosions and jets from supermassive black holes, that create neutrinos, this approach has helped astronomers pinpoint the distant sources and each additional messenger provides additional clues about the details of the phenomena.

For cosmic neutrinos above 100 TeV, previous research by the Penn State group [Nature Physics] showed that it is possible to have concordance with high-energy gamma rays and ultra-high-energy cosmic rays which fits with a multimessenger picture. However, there is growing evidence for an excess of neutrinos below 100 TeV, which cannot simply be explained. Very recently, the IceCube Neutrino Observatory reported another excess of high-energy neutrinos in the direction of one of the brightest active galaxies, known as NGC 1068, in the northern sky.

“We know that the sources of high-energy neutrinos must also create gamma rays, so the question is: Where are these missing gamma rays?” said Murase. “The sources are somehow hidden from our view in high-energy gamma rays, and the energy budget of neutrinos released into the universe is surprisingly large. The best candidates for this type of source have dense environments, where gamma rays would be blocked by their interactions with radiation and matter but neutrinos can readily escape. Our new model shows that supermassive black hole systems are promising sites and the model can explain the neutrinos below 100 TeV with modest energetics requirements.”

The new model suggests that the corona — the aura of superhot plasma that surrounds stars and other celestial bodies — around supermassive black holes found at the core of galaxies, could be such a source. Analogous to the corona seen in a picture of the Sun during a solar eclipse, astrophysicists believe that black holes have a corona above the rotating disk of material, known as an accretion disk, that forms around the black hole through its gravitational influence. This corona is extremely hot (with a temperature of about one billion degrees kelvin), magnetized, and turbulent. In this environment, particles can be accelerated, which leads to particle collisions that would create neutrinos and gamma rays, but the environment is dense enough to prevent the escape of high-energy gamma rays.

“The model also predicts electromagnetic counterparts of the neutrino sources in ‘soft’ gamma-rays instead of high-energy gamma rays,” said Murase. “High-energy gamma rays would be blocked but this is not the end of the story. They would eventually be cascaded down to lower energies and released as ‘soft’ gamma rays in the megaelectron volt range, but most of the existing gamma-ray detectors, like the Fermi Gamma-ray Space Telescope, are not tuned to detect them.”

There are projects under development that are designed specifically to explore such soft gamma-ray emission from space. Furthermore, upcoming and next-generation neutrino detectors, KM3Net in the Mediterranean Sea and IceCube-Gen2 in Antarctica will be more sensitive to the sources.

Artist’s expression of the KM3NeT neutrino telescope

IceCube Gen-2 DeepCore anotated

The promising targets include NGC 1068 in the northern sky, for which the excess neutrino emission was reported, and several of the brightest active galaxies in the southern sky.

“These new gamma-ray and neutrino detectors will enable deeper searches for multimessenger emission from supermassive black hole coronae,” said Murase. “This will make it possible to critically examine if these sources are responsible for the large flux of mid-energy level neutrinos observed by IceCube as our model predicts.”

In addition to Murase, the research team at Penn State includes the former IGC fellow Shigeo S. Kimura and Eberly Chair Professor Emeritus Peter Mészáros.

The Alfred P. Sloan Foundation, the U.S. National Science Foundation, the Japanese Society for the Promotion of Science, NASA, the Penn State Institute for Gravitation and the Cosmos, and the Eberly Foundation funded this work.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

About Penn State

WHAT WE DO BEST

We teach students that the real measure of success is what you do to improve the lives of others, and they learn to be hard-working leaders with a global perspective. We conduct research to improve lives. We add millions to the economy through projects in our state and beyond. We help communities by sharing our faculty expertise and research.

Penn State lives close by no matter where you are. Our campuses are located from one side of Pennsylvania to the other. Through Penn State World Campus, students can take courses and work toward degrees online from anywhere on the globe that has Internet service.

We support students in many ways, including advising and counseling services for school and life; diversity and inclusion services; social media sites; safety services; and emergency assistance.

Our network of more than a half-million alumni is accessible to students when they want advice and to learn about job networking and mentor opportunities as well as what to expect in the future. Through our alumni, Penn State lives all over the world.

The best part of Penn State is our people. Our students, faculty, staff, alumni, and friends in communities near our campuses and across the globe are dedicated to education and fostering a diverse and inclusive environment.

From Vanderbilt University: “To find giant black holes, start with Jupiter”

From Vanderbilt University

Jun. 30, 2020
Marissa Shapiro

The revolution in our understanding of the night sky and our place in the universe began when we transitioned from using the naked eye to a telescope in 1609. Four centuries later, scientists are experiencing a similar transition in their knowledge of black holes by searching for gravitational waves.

In the search for previously undetected b lack holes that are billions of times more massive than the sun, assistant professor of physics Stephen Taylor and astronomy and former astronomer at NASA’s Jet Propulsion Laboratory (JPL) together with the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration has moved the field of research forward by finding the precise location – the center of gravity of our solar system – with which to measure the gravitational waves that signal the existence of these black holes.

The potential presented by this advancement, co-authored by Taylor, was published in The Astrophysical Journal in April 2020.

Black holes are regions of pure gravity formed from extremely warped spacetime. Finding the most titanic black holes in the Universe that lurk at the heart of galaxies will help us understand how such galaxies (including our own) have grown and evolved over the billions of years since their formation. These black holes are also unrivaled laboratories for testing fundamental assumptions about physics.

Gravitational waves are ripples in spacetime predicted by Einstein’s general theory of relativity. When black holes orbit each other in pairs, they radiate gravitational waves that deform spacetime, stretching and squeezing space. Gravitational waves were first detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2015, opening new vistas on the most extreme objects in the universe.

Caltech/MIT Advanced aLigo Hanford, WA, USA installation

Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

ESA/eLISA the future of gravitational wave research

Whereas LIGO observes relatively short gravitational waves by looking for changes in the shape of a 4-km long detector, NANOGrav, a National Science Foundation (NSF) Physics Frontiers Center, looks for changes in the shape of our entire galaxy.

NANOGrave Gravitational waves JPL-Caltech. Detecting gravitational waves using an array of pulsars (David Champion)

Taylor and his team are searching for changes to the arrival rate of regular flashes of radio waves from pulsars. These pulsars are rapidly spinning neutron stars, some going as fast as a kitchen blender. They also send out beams of radio waves, appearing like interstellar lighthouses when these beams sweep over Earth. Over 15 years of data have shown that these pulsars are extremely reliable in their pulse arrival rates, acting as outstanding galactic clocks. Any timing deviations that are correlated across lots of these pulsars could signal the influence of gravitational waves warping our galaxy.

“Using the pulsars we observe across the Milky Way galaxy, we are trying to be like a spider sitting in stillness in the middle of her web,” explains Taylor. “How well we understand the solar system barycenter is critical as we attempt to sense even the smallest tingle to the web.” The solar system barycenter, its center of gravity, is the location where the masses of all planets, moons, and asteroids balance out.

Where is the center of our web, the location of absolute stillness in our solar system? Not in the center of the sun as many might assume, rather it is closer to the surface of the star. This is due to Jupiter’s mass and our imperfect knowledge of its orbit. It takes 12 years for Jupiter to orbit the sun, just shy of the 15 years that NANOGrav has been collecting data. JPL’s Galileo probe (named for the famed scientist that used a telescope to observe the moons of Jupiter) studied Jupiter between 1995 and 2003, but experienced technical maladies that impacted the quality of the measurements taken during the mission.

NASA/Galileo 1989-2003

Identifying the center of the solar system’s gravity has long been calculated with data from Doppler tracking to get an estimate of the location and trajectories of bodies orbiting the sun. “The catch is that errors in the masses and orbits will translate to pulsar-timing artifacts that may well look like gravitational waves,” explains JPL astronomer and co-author Joe Simon.

Taylor and his collaborators were finding that working with existing solar system models to analyze NANOGrav data gave inconsistent results. “We weren’t detecting anything significant in our gravitational wave searches between solar system models, but we were getting large systematic differences in our calculations,” notes JPL astronomer and the paper’s lead author Michele Vallisneri. “Typically, more data delivers a more precise result, but there was always an offset in our calculations.”

The group decided to search for the center of gravity of the solar system at the same time as sleuthing for gravitational waves. The researchers got more robust answers to finding gravitational waves and were able to more accurately localize the center of the solar system’s gravity to within 100 meters. To understand that scale, if the sun were the size of a football field, 100 meters would be the diameter of a strand of hair. “Our precise observation of pulsars scattered across the galaxy has localized ourselves in the cosmos better than we ever could before,” said Taylor. “By finding gravitational waves this way, in addition to other experiments, we gain a more holistic overview of all different kinds of black holes in the Universe.”

As NANOGrav continues to collect ever more abundant and precise pulsar timing data, astronomers are confident that massive black holes will show up soon and unequivocally in the data.

Taylor was partially supported by an appointment to the NASA Postdoctoral Program at JPL. The NANOGrav project receives support from the NSF Physics Frontier Center award #1430284 and this work was supported in part by NSF Grant PHYS-1066293 and by the hospitality of the Aspen Center for Physics. Data for this project were collected using the facilities of the Green Bank Observatory and the Arecibo Observatory.

GBO radio telescope, Green Bank, West Virginia, USA

NAIC Arecibo Observatory operated by University of Central Florida, Yang Enterprises and UMET, Altitude 497 m (1,631 ft).

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Commodore Cornelius Vanderbilt was in his 79th year when he decided to make the gift that founded Vanderbilt University in the spring of 1873.
The $1 million that he gave to endow and build the university was the commodore’s only major philanthropy. Methodist Bishop Holland N. McTyeire of Nashville, husband of Amelia Townsend who was a cousin of the commodore’s young second wife Frank Crawford, went to New York for medical treatment early in 1873 and spent time recovering in the Vanderbilt mansion. He won the commodore’s admiration and support for the project of building a university in the South that would “contribute to strengthening the ties which should exist between all sections of our common country.”

McTyeire chose the site for the campus, supervised the construction of buildings and personally planted many of the trees that today make Vanderbilt a national arboretum. At the outset, the university consisted of one Main Building (now Kirkland Hall), an astronomical observatory and houses for professors. Landon C. Garland was Vanderbilt’s first chancellor, serving from 1875 to 1893. He advised McTyeire in selecting the faculty, arranged the curriculum and set the policies of the university.

For the first 40 years of its existence, Vanderbilt was under the auspices of the Methodist Episcopal Church, South. The Vanderbilt Board of Trust severed its ties with the church in June 1914 as a result of a dispute with the bishops over who would appoint university trustees.

From the outset, Vanderbilt met two definitions of a university: It offered work in the liberal arts and sciences beyond the baccalaureate degree and it embraced several professional schools in addition to its college. James H. Kirkland, the longest serving chancellor in university history (1893-1937), followed Chancellor Garland. He guided Vanderbilt to rebuild after a fire in 1905 that consumed the main building, which was renamed in Kirkland’s honor, and all its contents. He also navigated the university through the separation from the Methodist Church. Notable advances in graduate studies were made under the third chancellor, Oliver Cromwell Carmichael (1937-46). He also created the Joint University Library, brought about by a coalition of Vanderbilt, Peabody College and Scarritt College.

Remarkable continuity has characterized the government of Vanderbilt. The original charter, issued in 1872, was amended in 1873 to make the legal name of the corporation “The Vanderbilt University.” The charter has not been altered since.

The university is self-governing under a Board of Trust that, since the beginning, has elected its own members and officers. The university’s general government is vested in the Board of Trust. The immediate government of the university is committed to the chancellor, who is elected by the Board of Trust.

The original Vanderbilt campus consisted of 75 acres. By 1960, the campus had spread to about 260 acres of land. When George Peabody College for Teachers merged with Vanderbilt in 1979, about 53 acres were added.

Vanderbilt’s student enrollment tended to double itself each 25 years during the first century of the university’s history: 307 in the fall of 1875; 754 in 1900; 1,377 in 1925; 3,529 in 1950; 7,034 in 1975. In the fall of 1999 the enrollment was 10,127.

In the planning of Vanderbilt, the assumption seemed to be that it would be an all-male institution. Yet the board never enacted rules prohibiting women. At least one woman attended Vanderbilt classes every year from 1875 on. Most came to classes by courtesy of professors or as special or irregular (non-degree) students. From 1892 to 1901 women at Vanderbilt gained full legal equality except in one respect — access to dorms. In 1894 the faculty and board allowed women to compete for academic prizes. By 1897, four or five women entered with each freshman class. By 1913 the student body contained 78 women, or just more than 20 percent of the academic enrollment.

National recognition of the university’s status came in 1949 with election of Vanderbilt to membership in the select Association of American Universities. In the 1950s Vanderbilt began to outgrow its provincial roots and to measure its achievements by national standards under the leadership of Chancellor Harvie Branscomb. By its 90th anniversary in 1963, Vanderbilt for the first time ranked in the top 20 private universities in the United States.

Vanderbilt continued to excel in research, and the number of university buildings more than doubled under the leadership of Chancellors Alexander Heard (1963-1982) and Joe B. Wyatt (1982-2000), only the fifth and sixth chancellors in Vanderbilt’s long and distinguished history. Heard added three schools (Blair, the Owen Graduate School of Management and Peabody College) to the seven already existing and constructed three dozen buildings. During Wyatt’s tenure, Vanderbilt acquired or built one-third of the campus buildings and made great strides in diversity, volunteerism and technology.

The university grew and changed significantly under its seventh chancellor, Gordon Gee, who served from 2000 to 2007. Vanderbilt led the country in the rate of growth for academic research funding, which increased to more than $450 million and became one of the most selective undergraduate institutions in the country.

On March 1, 2008, Nicholas S. Zeppos was named Vanderbilt’s eighth chancellor after serving as interim chancellor beginning Aug. 1, 2007. Prior to that, he spent 2002-2008 as Vanderbilt’s provost, overseeing undergraduate, graduate and professional education programs as well as development, alumni relations and research efforts in liberal arts and sciences, engineering, music, education, business, law and divinity. He first came to Vanderbilt in 1987 as an assistant professor in the law school. In his first five years, Zeppos led the university through the most challenging economic times since the Great Depression, while continuing to attract the best students and faculty from across the country and around the world. Vanderbilt got through the economic crisis notably less scathed than many of its peers and began and remained committed to its much-praised enhanced financial aid policy for all undergraduates during the same timespan. The Martha Rivers Ingram Commons for first-year students opened in 2008 and College Halls, the next phase in the residential education system at Vanderbilt, is on track to open in the fall of 2014. During Zeppos’ first five years, Vanderbilt has drawn robust support from federal funding agencies, and the Medical Center entered into agreements with regional hospitals and health care systems in middle and east Tennessee that will bring Vanderbilt care to patients across the state.

Today, Vanderbilt University is a private research university of about 6,500 undergraduates and 5,300 graduate and professional students. The university comprises 10 schools, a public policy center and The Freedom Forum First Amendment Center. Vanderbilt offers undergraduate programs in the liberal arts and sciences, engineering, music, education and human development as well as a full range of graduate and professional degrees. The university is consistently ranked as one of the nation’s top 20 universities by publications such as U.S. News & World Report, with several programs and disciplines ranking in the top 10.

Cutting-edge research and liberal arts, combined with strong ties to a distinguished medical center, creates an invigorating atmosphere where students tailor their education to meet their goals and researchers collaborate to solve complex questions affecting our health, culture and society.

Vanderbilt, an independent, privately supported university, and the separate, non-profit Vanderbilt University Medical Center share a respected name and enjoy close collaboration through education and research. Together, the number of people employed by these two organizations exceeds that of the largest private employer in the Middle Tennessee region.

From Max Planck Gesellschaft and Northwestern University: “A black hole with a puzzling companion”

From Max Planck Gesellschaft

and

Northwestern University

June 23, 2020

Media contacts

Dr. Benjamin Knispel
Press and Public Relations Officer
+49 511 762-19104
benjamin.knispel@aei.mpg.de
Albert-Einstein-Institut , Hannover

Dr. Elke Müller
Press Officer Max Planck Institute for Gravitational Physics, Potsdam-Golm
+49 331 567-7303
elke.mueller@aei.mpg.de

Scientific contacts
Prof. Dr. Alessandra Buonanno
Max Planck Institute for Gravitational Physics, Potsdam-Golm
+49 331 567-7220
alessandra.buonanno@aei.mpg.de

Prof. Dr. Karsten Danzmann
Max Planck Institute for Gravitational Physics (Hannover), Hannover
+49 511 762-2356
karsten.danzmann@aei.mpg.de

Dr. Frank Ohme
Max Planck Institute for Gravitational Physics (Hannover), Hannover
+49 511 762-17171
frank.ohme@aei.mpg.de

Dr. Jonathan Gair
Max Planck Institute for Gravitational Physics, Potsdam-Golm
+49 331 567-7305
jonathan.gair@aei.mpg.de

LIGO and Virgo find another surprising binary system.

MIT /Caltech Advanced aLigo

VIRGO Gravitational Wave interferometer, near Pisa, Italy

The harvest of exceptional gravitational-wave events from LIGO’s and Virgo’s third observing run (O3) grows. A new signal published today [ The Astrophysical Letters ] comes from the merger of a 23-solar-mass black hole with an object 9 times lighter. The second object is mysterious: its measured mass puts it in the so-called “mass gap” between the heaviest known neutron stars and the lightest known black holes. While the researchers cannot be sure about its true nature, one thing is clear: the observation of this unusual pair challenges the current understanding of how such systems are born and evolve.

Visualization of the coalescence of two black holes that inspiral and merge, emitting gravitational waves. One black hole is 9.2 times more massive than the other and both objects are non-spinning.
© N. Fischer, S. Ossokine, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes (SXS) Collaboration

“GW190814 is an unexpected and a really exciting discovery,” says Abhirup Ghosh, a post-doctoral researcher in the “Astrophysical and Cosmological Relativity” division at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Potsdam. “It is unique because of two outstanding features. Never before have we witnessed a gravitational-wave signal from a system in which the individual masses are this different: a black hole 23 times the mass of our Sun merging with an object just 2.6 times the mass of the Sun. But what adds to the mystery is that we are not sure about the nature of the lighter object. If it’s indeed a black hole, it’s the lightest, and if it’s a neutron star it’s the most massive we have ever observed in a binary system of two compact objects.”

Because of the unequal masses, the telltale fingerprints of the neutron star’s tidal deformation that would give away its presence are hard to detect – and were not seen – in GW190814. Therefore, it remains unclear whether the lighter object is a black hole or a neutron star. If it actually is a neutron star, it would be exceptionally massive and would challenge our understanding of how neutron-star matter behaves and how massive these objects can be.

“Because the objects’ masses are so different, we clearly identified the gravitational-wave hum of a higher harmonic, which is similar to overtones of musical instruments,” says Jonathan Gair, group leader in the “Astrophysical and Cosmological Relativity” division at the AEI in Potsdam. “These harmonics – seen in GW190814 only for the second time ever – allow us to more precisely measure some astrophysical properties of the binary system and enable new tests of Einstein’s theory of general relativity.”

GW190814 was observed by both LIGO detectors and the Virgo detector on 14th of August 2019, during the detectors’ third observing run O3 – to the day two years after GW170814, the first signal observed by all three instruments.

“Due to the favourable circumstance of having observed such a loud signal with quite different component masses and for about 10 seconds, we achieved the most precise gravitational-wave measurement of a black hole spin to date,” explains Alessandra Buonanno, director of the “Astrophysical and Cosmological Relativity” division at the AEI in Potsdam. “This is important, because the spin of a black hole carries information about its birth and evolution. We find that this 23-solar-mass black hole spins rather slowly: less than 7% of the maximum spin allowed by general relativity.”

“Knowing in which environment this unusual binary system was born and how it evolved is really hard. It’s unlike most of the systems we know from simulations of the binary merger population,” says Frank Ohme, leader of an independent Max Planck Research Group at AEI Hannover. “GW190814 and similar future signals could help us to better understand this unexpected new kind of binary system and the processes which give birth to massive neutron stars or light-weight black holes,” he adds.

The astronomers’ best guess is that the system formed either in young, dense star clusters or the surroundings of active galactic nuclei. Based on their estimates of how many such systems exist in the Universe and how often they merge, they expect to observe more such systems in future LIGO/Virgo observing runs.

Each of these four images shows a different mode (or overtone) of the gravitational-wave signal in a different color. From left to right and top to bottom, the panels show the quadrupolar (orange), octupolar (magenta), hexadecupolar (purple) and 32-polar (blue) modes.
© N. Fischer, S. Ossokine, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes (SXS) Collaboration

The unequal masses imprint themselves on the emitted gravitational-wave signal, which in turn allows scientists to more precisely determine some of its astrophysical properties, such as the distance to the system.

Detailed analyses of the LIGO and Virgo data show that the merger happened at a distance of about 780 million light-years from Earth. Its sky position could be determined to an area equivalent to approximately 90 full moons towards the southern-sky constellation “Sculptor”.

AEI researchers contributed to detecting and analyzing GW190814. They have provided accurate models of the gravitational waves from coalescing black holes that included, for the first time, the precession of the black-holes’ spins, multipole moments beyond the dominant quadrupole, as well as tidal effects introduced by the potential neutron-star companion. Those features imprinted in the waveform are crucial to extract unique information about the source’s properties and carry out tests of general relativity. The high-performance computer clusters “Minerva” and “Hypatia” at AEI Potsdam were employed to develop the waveform models used for the analyses.

With the distance and the sky position precisely determined, LIGO and Virgo scientists also used GW190814 (and their earlier observation of a binary neutron star merger) to obtain a new gravitational-wave measurement of the Hubble constant, the rate at which the Universe expands. The result improves on previous such gravitational wave determinations; it is less precise than but in agreement with other Hubble constant measurements.

LIGO and Virgo scientists also used GW190814 to look for deviations of the signal from predictions of Einstein’s general theory of relativity. Even this unusual signal that represents a new type of binary merger follows the theory’s predictions.

This discovery is the third reported from the third observing run (O3) of the international gravitational-wave detector network. Scientists at the three large detectors have made several technological upgrades to the instruments.

“In O3 we used squeezed light to enhance the sensitivity of LIGO and Virgo by 40%. We pioneered this technique of carefully tuning the quantum-mechanical properties of the laser light at the German-British detector GEO600,” explains Karsten Danzmann, director at the AEI Hannover and director of the Institute for Gravitational Physics at Leibniz University Hannover. “The AEI is leading the world-wide efforts to maximize the degree of squeezing and our advances in this technology will benefit all future gravitational-wave detectors.”

The LIGO and Virgo researchers have issued alerts for 56 possible gravitational-wave events (candidates) in O3, which lasted from 1 April 2019 to 27 March 2020. So far, three candidates have been confirmed and made public. LIGO and Virgo scientists are examining all remaining 53 candidates and will publish all those for which detailed follow-up analyses confirm their astrophysical origin.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

The Max Planck Society is Germany’s most successful research organization. Since its establishment in 1948, no fewer than 18 Nobel laureates have emerged from the ranks of its scientists, putting it on a par with the best and most prestigious research institutions worldwide. The more than 15,000 publications each year in internationally renowned scientific journals are proof of the outstanding research work conducted at Max Planck Institutes – and many of those articles are among the most-cited publications in the relevant field.

What is the basis of this success? The scientific attractiveness of the Max Planck Society is based on its understanding of research: Max Planck Institutes are built up solely around the world’s leading researchers. They themselves define their research subjects and are given the best working conditions, as well as free reign in selecting their staff. This is the core of the Harnack principle, which dates back to Adolph von Harnack, the first president of the Kaiser Wilhelm Society, which was established in 1911. This principle has been successfully applied for nearly one hundred years. The Max Planck Society continues the tradition of its predecessor institution with this structural principle of the person-centered research organization.

The currently 83 Max Planck Institutes and facilities conduct basic research in the service of the general public in the natural sciences, life sciences, social sciences, and the humanities. Max Planck Institutes focus on research fields that are particularly innovative, or that are especially demanding in terms of funding or time requirements. And their research spectrum is continually evolving: new institutes are established to find answers to seminal, forward-looking scientific questions, while others are closed when, for example, their research field has been widely established at universities. This continuous renewal preserves the scope the Max Planck Society needs to react quickly to pioneering scientific developments.

South Campus

On May 31, 1850, nine men gathered to begin planning a university that would serve the Northwest Territory.

Given that they had little money, no land and limited higher education experience, their vision was ambitious. But through a combination of creative financing, shrewd politicking, religious inspiration and an abundance of hard work, the founders of Northwestern University were able to make that dream a reality.

In 1853, the founders purchased a 379-acre tract of land on the shore of Lake Michigan 12 miles north of Chicago. They established a campus and developed the land near it, naming the surrounding town Evanston in honor of one of the University’s founders, John Evans. After completing its first building in 1855, Northwestern began classes that fall with two faculty members and 10 students.
Twenty-one presidents have presided over Northwestern in the years since. The University has grown to include 12 schools and colleges, with additional campuses in Chicago and Doha, Qatar.

Northwestern is recognized nationally and internationally for its educational programs.

From University of Birmingham UK via phys.org: “New gravitational-wave model can bring neutron stars into even sharper focus”

From University of Birmingham UK

via

phys.org

May 21, 2020

The results from a numerical relativity simulation of two merging neutron stars similar to GW170817. Credit: University of Birmingham

Gravitational-wave researchers at the University of Birmingham have developed a new model that promises to yield fresh insights into the structure and composition of neutron stars.

The model shows that vibrations, or oscillations, inside the stars can be directly measured from the gravitational-wave signal alone. This is because neutron stars will become deformed under the influence of tidal forces, causing them to oscillate at characteristic frequencies, and these encode unique information about the star in the gravitational-wave signal.

This makes asteroseismology—the study of stellar oscillations—with gravitational waves from colliding neutron stars a promising new tool to probe the elusive nature of extremely dense nuclear matter.

Neutron stars are the ultradense remnants of collapsed massive stars. They have been observed in the thousands in the electromagnetic spectrum and yet little is known about their nature. Unique information can be gleaned through measuring the gravitational waves emitted when two neutron stars meet and form a binary system. First predicted by Albert Einstein, these ripples in spacetime were first detected by the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO) in 2015.

By utilising the gravitational wave signal to measure the oscillations of the neutron stars, researchers will be able to discover new insights into the interior of these stars. The study is published in Nature Communications.

Dr. Geraint Pratten, of the University of Birmingham’s Gravitational Wave Institute, is lead author of the study. He explained: “As the two stars spiral around each other, their shapes become distorted by the gravitational force exerted by their companion. This becomes more and more pronounced and leaves a unique imprint in the gravitational wave signal.

“The tidal forces acting on the neutron stars excite oscillations inside the star giving us insight into their internal structure. By measuring these oscillations from the gravitational-wave signal, we can extract information about the fundamental nature and composition of these mysterious objects that would otherwise be inaccessible.”

The model developed by the team enables the frequency of these oscillations to be determined directly from gravitational-wave measurements for the first time. The researchers used their model on the first observed gravitational-wave signal from a binary neutron star merger—GW170817.

Co-lead author, Dr. Patricia Schmidt, added: “Almost three years after the first gravitational-waves from a binary neutron star were observed, we are still finding new ways to extract more information about them from the signals. The more information we can gather by developing ever more sophisticated theoretical models, the closer we will get to revealing the true nature of neutron stars.”

Next generation gravitational wave observatories planned for the 2030s, will be capable of detecting far more binary neutron stars and observing them in much greater detail than is currently possible. The model produced by the Birmingham team will make a significant contribution to this science.

“The information from this initial event was limited as there was quite a lot of background noise that made the signal difficult to isolate,” says Dr. Pratten. “With more sophisticated instruments we can measure the frequencies of these oscillations much more precisely and this should start to yield some really interesting insights.”

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Birmingham has been challenging and developing great minds for more than a century. Characterised by a tradition of innovation, research at the University has broken new ground, pushed forward the boundaries of knowledge and made an impact on people’s lives. We continue this tradition today and have ambitions for a future that will embed our work and recognition of the Birmingham name on the international stage.

From ARC Centres of Excellence for Gravitational Wave Discovery: “Scientists reveal new insights of exploding massive stars and future gravitational-wave detectors”

From ARC Centres of Excellence for Gravitational Wave Discovery

Artist’s impression of a supernova. Source: Pixabay

11/5/2020

​
​In a study recently published in the Monthly Notices of the Royal Astronomical Society, researchers Dr Jade Powell and Dr Bernhard Mueller from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) simulated three core-collapse supernovae using supercomputers from across Australia, including the OzSTAR supercomputer at Swinburne University of Technology. The simulation models—which are 39 times, 20 times and 18 times more massive than our Sun— revealed new insights into exploding massive stars and the next generation of gravitational-wave detectors.

Core-collapse supernovae are the explosive deaths of massive stars at the end of their lifetime. They are some of the most luminous objects in the Universe and are the birthplace of black holes and neutron stars. The gravitational waves—ripples in space and time—detected from these supernovae, help scientists better understand the astrophysics of black holes and neutron stars.

A 3D-volume render of a core-collapse supernova. Credit: Bernhard Mueller, Monash University

Future advanced gravitational-wave detectors, engineered to be more sensitive, could possibly detect a supernova—a core-collapse supernova could be the first object to be observed simultaneously in electromagnetic light, neutrinos and gravitational waves.

To detect a core-collapse supernova in gravitational waves, scientists need to predict what the gravitational wave signal will look like. Supercomputers are used to simulate these cosmic explosions to understand their complicated physics. This allows scientists to predict what the detectors will see when a star explodes and its observable properties.

In the study, the simulations of three exploding massive stars follow the operation of the supernova engine over a long duration—this is important for accurate predictions of the neutron star masses and observable explosion energy.

OzGrav postdoctoral researcher Jade Powell says: ‘Our models are 39 times, 20 times and 18 times more massive than our Sun. The 39-solar mass model is important because it’s rotating very rapidly, and most previous long duration core-collapse supernova simulations do not include the effects of rotation’.

The two most massive models produce energetic explosions powered by the neutrinos, but the smallest model did not explode. Stars that do not explode emit lower amplitude gravitational waves, but the frequency of their gravitational waves lies in the most sensitive range of gravitational wave detectors.

‘For the first time, we showed that rotation changes the relationship between the gravitational-wave frequency and the properties of the newly-forming neutron star,’ explains Powell.

The rapidly rotating model showed large gravitational-wave amplitudes that would make the exploding star detectable almost 6.5 million light years away by the next generation of gravitational-wave detectors, like the Einstein Telescope.

Depiction of the ASPERA Albert Einstein Telescope, Albert Einstein Institute Hannover and Max Planck Institute for Gravitational Physics and Leibniz Universitat Hannover

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

OzGrav

THE ARC CENTRE of excellence FOR GRAVITATIONAL WAVE DISCOVERY
A new window of discovery.
A new age of gravitational wave astronomy.
One hundred years ago, Albert Einstein produced one of the greatest intellectual achievements in physics, the theory of general relativity. In general relativity, spacetime is dynamic. It can be warped into a black hole. Accelerating masses create ripples in spacetime known as gravitational waves (GWs) that carry energy away from the source. Recent advances in detector sensitivity led to the first direct detection of gravitational waves in 2015. This was a landmark achievement in human discovery and heralded the birth of the new field of gravitational wave astronomy. This was followed in 2017 by the first observations of the collision of two neutron-stars. The accompanying explosion was subsequently seen in follow-up observations by telescopes across the globe, and ushered in a new era of multi-messenger astronomy.

The mission of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is to capitalise on the historic first detections of gravitational waves to understand the extreme physics of black holes and warped spacetime, and to inspire the next generation of Australian scientists and engineers through this new window on the Universe.

OzGrav is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme, and is a partnership between Swinburne University (host of OzGrav headquarters), the Australian National University, Monash University, University of Adelaide, University of Melbourne, and University of Western Australia, along with other collaborating organisations in Australia and overseas.

________________________________________________________

The objectives for the ARC Centres of Excellence are to to:

undertake highly innovative and potentially transformational research that aims to achieve international standing in the fields of research envisaged and leads to a significant advancement of capabilities and knowledge
link existing Australian research strengths and build critical mass with new capacity for interdisciplinary, collaborative approaches to address the most challenging and significant research problems
develope relationships and build new networks with major national and international centres and research programs to help strengthen research, achieve global competitiveness and gain recognition for Australian research
build Australia’s human capacity in a range of research areas by attracting and retaining, from within Australia and abroad, researchers of high international standing as well as the most promising research students
provide high-quality postgraduate and postdoctoral training environments for the next generation of researchers
offer Australian researchers opportunities to work on large-scale problems over long periods of time
establish Centres that have an impact on the wider community through interaction with higher education institutes, governments, industry and the private and non-profit sector.

From National Astronomical Observatory of Japan: “TAMA300 Blazes Trail for Improved Gravitational Wave Astronomy”

Figure: Vacuum chambers in the infrastructure of the former TAMA300 detector used in this experiment. (Credit: NAOJ)

From National Astronomical Observatory of Japan

April 28, 2020

Figure: Vacuum chambers in the infrastructure of the former TAMA300 detector used in this experiment. (Credit: NAOJ)

Researchers at the National Astronomical Observatory of Japan (NAOJ) have used the infrastructure of the former TAMA300 gravitational wave detector in Mitaka, Tokyo to demonstrate a new technique to reduce quantum noise in detectors. This new technique will help increase the sensitivity of the detectors comprising a collaborative worldwide gravitational wave network, allowing them to observe fainter waves.

When it began observations in 2000, TAMA300 was one of the world’s first large-scale interferometric gravitational wave detectors. At that time TAMA300 had the highest sensitivity in the world, setting an upper limit on the strength of gravitational wave signals; but the first detection of actual gravitational waves was made 15 years later in 2015 by LIGO. Since then detector technology has improved to the point that modern detectors are observing several signals per month. The scientific results obtained from these observations are already impressive and many more are expected in the next decades. TAMA300 is no longer participating in observations, but is still active, acting as a testbed for new technologies to improve other detectors.

The sensitivity of current and future gravitational wave detectors is limited at almost all the frequencies by quantum noise caused by the effects of vacuum fluctuations of the electromagnetic fields. But even this inherent quantum noise can be sidestepped. It is possible to manipulate the vacuum fluctuations to redistribute the quantum uncertainties, deceasing one type of noise at the expense of increasing a different, less obstructive type of noise. This technique, known as vacuum squeezing, has already been implemented in gravitational wave detectors, greatly increasing their sensitivity to higher frequency gravitational waves. But the optomechanical interaction between the electromagnetic field and the mirrors of the detector cause the effects of vacuum squeezing to change depending on the frequency. So at low frequencies vacuum squeezing increases the wrong type of noise, actually degrading sensitivity.

To overcome this limitation and achieve reduced noise at all frequencies, a team at NAOJ composed of members of the in-house Gravitational Wave Science Project and the KAGRA collaboration (but also including researchers of the Virgo and GEO collaborations) has recently demonstrated the feasibility of a technique known as frequency dependent vacuum squeezing, at the frequencies useful for gravitational wave detectors. Because the detector itself interacts with the electromagnetic fields differently depending on the frequency, the team used the infrastructure of the former TAMA300 detector to create a field which itself varies depending on frequency. A normal (frequency independent) squeezed vacuum field is reflected off an optical cavity 300-m long, such that a frequency dependence is imprinted and it is able counteract the optomechanical effect of the interferometer.

This technique will allow improved sensitivity at both high and low frequencies simultaneously. This is a crucial result demonstrating a key-technology to improve the sensitivity of future detectors. Its implementation, planned as a near term upgrade together with other improvements, is expected to double the observation range of second-generation detectors.

These results will appear as Zhao, Y., et al. “Frequency-dependent squeezed vacuum source for broadband quantum noise reduction in advanced gravitational-wave detectors” in Physical Review Letters on April 28, 2020. A similar result has been obtained by a group in MIT using a 16-m filter cavity, and the two papers will be published jointly.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

NAOJ

The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level

ESO/NRAO/NAOJ ALMA Array

Solar Flare Telescope

Nobeyama Millimeter Array Radioheliograph, located near Minamimaki, Nagano at an elevation of 1350m

Mizusawa VERA Observatory

Okayama Astrophysical Observatory

From Max Planck Institute for Gravitational Physics : “A signal like none before”

From Max Planck Institute for Gravitational Physics

April 20, 2020

Media Contacts

Dr. Benjamin Knispel
Press Officer AEI Hannover
Phone:+49 511 762-19104Fax:+49 511 762-17182
benjamin.knispel@aei.mpg.de

Dr. Elke Müller
Press Officer AEI Potsdam
Phone:+49 331 567-7303Fax:+49 331 567-7298
elke.mueller@aei.mpg.de

Science Contacts

Prof. Dr. Alessandra Buonanno
Director
Phone:+49 331 567-7220Fax:+49 331 567-7298
alessandra.buonanno@aei.mpg.de
LSC Principal Investigator

Prof. Dr. Karsten Danzmann
Director
Phone:+49 511 762-2356Fax:+49 511 762-5861
karsten.danzmann@aei.mpg.de
LSC Principal Investigator

Dr. Frank Ohme
Research Group Leader
Phone:+49 511 762-17171Fax:+49 511 762-2784
frank.ohme@aei.mpg.de
LSC Principal Investigator

Publication

The LIGO Scientific Collaboration and the Virgo Collaboration
GW190412: Observation of a Binary-Black-Hole Coalescence with Asymmetric Masses
arXiv:2004.08342

The expectations of the gravitational-wave research community have been fulfilled: gravitational-wave discoveries are now part of their daily work as they have identified in the past observing run, O3, new gravitational-wave candidates about once a week. But now, the researchers have published a remarkable signal unlike any of those seen before: GW190412 is the first observation of a binary black hole merger where the two black holes have distinctly different masses of about 8 and 30 times that of our Sun. This not only has allowed more precise measurements of the system’s astrophysical properties, but it has also enabled the LIGO/Virgo scientists to verify a so far untested prediction of Einstein’s theory of general relativity.

Binary black hole merger where the two black holes have distinctly different masses of about 8 and 30 times that of our Sun.
© N. Fischer, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes project.

“For the very first time we have ‘heard’ in GW190412 the unmistakable gravitational-wave hum of a higher harmonic, similar to overtones of musical instruments,” explains Frank Ohme, leader of the Independent Max Planck Research Group “Binary Merger Observations and Numerical Relativity” at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover. “In systems with unequal masses like GW190412 – our first observation of this type – these overtones in the gravitational-wave signal are much louder than in our usual observations. This is why we couldn’t hear them before, but in GW190412, we finally can.” This observation once again confirms Einstein’s theory of general relativity, which predicts the existence of these higher harmonics, i.e. gravitational waves at two or three times the fundamental frequency observed so far.

“The black holes at the heart of GW190412 have 8 and 30 times the mass of our Sun, respectively. This is the first binary black-hole system we have observed for which the difference between the masses of the two black holes is so large!” says Roberto Cotesta, a PhD student in the “Astrophysical and Cosmological Relativity” division at the AEI in Potsdam. “This big mass difference means that we can more precisely measure several properties of the system: its distance to us, the angle we look at it, and how fast the heavy black hole spins around its axis.”

© N. Fischer, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes project
GW190412: Binary Black Hole Merger
Numerical simulation of a black-hole binary merger with asymmetric masses and orbital precession (GW190412).

GW190412 was observed by both LIGO detectors and the Virgo detector on 12th of April 2019, early during the detectors’ third observation run O3. Analyses reveal that the merger happened at a distance of 1.9 to 2.9 billion light-years from Earth. The new unequal mass system is a unique discovery since all binaries observed previously by the LIGO and Virgo detectors consisted of two roughly similar masses.

Unequal masses imprint themselves on the observed gravitational-wave signal, which in turn allow scientists to more precisely measure certain astrophysical properties of the system. The presence of higher harmonics makes it possible to break an ambiguity between the distance to the system and the angle we look at its orbital plane; therefore these properties can be measured with higher precision than in equal-mass systems without higher harmonics.

Numerical simulation of a black-hole binary merger with asymmetric masses and orbital precession (GW190412)
© N. Fischer, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes project.

“During O1 and O2, we have observed the tip of the iceberg of the binary population composed of stellar-mass black holes,” says Alessandra Buonanno, director of the “Astrophysical and Cosmological Relativity” division at the AEI in Potsdam and College Park professor at the University of Maryland. “Thanks to the improved sensitivity, GW190412 has begun to reveal us a more diverse, submerged population, characterized by mass asymmetry as large as 4 and black holes spinning at about 40% the possible maximum value allowed by general relativity,” she adds.

AEI researchers contributed to detecting and analyzing GW190412. They have provided accurate models of the gravitational waves from coalescing black holes that included, for the first time, both the precession of the black-holes’ spins and multipole moments beyond the dominant quadrupole. Those features imprinted in the waveform were crucial to extract unique information about the source’s properties and carry out tests of general relativity. The high-performance computer clusters “Minerva” and “Hypatia” at AEI Potsdam and “Holodeck” at AEI Hannover contributed significantly to the analysis of the signal.

Minerva

Hypatia

Testing Einstein’s theory

LIGO/Virgo scientists also used GW190412 to look for deviations of the signals from what Einstein’s general theory of relativity predicts. Even though the signal has properties unlike all others found so far, the researchers could find no significant departure from the general-relativistic predictions.

An improved international network of detectors using squeezed light

This discovery is the second reported from the third observation run (O3) of the international gravitational-wave detector network. Scientists at the three large detectors have made several technological upgrades to the instruments.

“During O3, squeezed light was used to enhance the sensitivity of LIGO and Virgo. This technique of carefully tuning the quantum-mechanical properties of the laser light was pioneered at the German-British detector GEO600,” explains Karsten Danzmann, director at the AEI Hannover and director of the Institute for Gravitational Physics at Leibniz University Hannover. “The AEI is leading the world-wide efforts to maximize the degree of squeezing, which has already improved the sensitivity of the GEO600 detector by a factor of two. Our advances in this technology will benefit all future gravitational-wave detectors.”

2 done, 54 on the to-do list

The detector network has issued alerts for 56 possible gravitational-wave events (candidates) in O3 (April 1, 2019 to March 27, 2020 with an interruption for upgrades and commissioning in October 2019). Out of these 56, one other confirmed signal, GW190425, has already been published. LIGO and Virgo scientists are examining all remaining 54 candidates and will publish all those for which detailed follow-up analyses confirm their astrophysical origin.

The observation of GW190412 means that similar systems are probably not as rare as predicted by some models. Therefore, with additional gravitational-wave observations and growing event catalogues in the future, more such signals are to be expected. Each of them could help astronomers better understand how black holes and their binary systems are formed, and shed new light on the fundamental physics of space-time.

___________________________________________________________
LIGO Scientific and Virgo Collaborations

LIGO is funded by the National Science Foundation (NSF) and operated by Caltech and MIT, which conceived of LIGO and lead the project.

Caltech/MIT Advanced aLigo Hanford, WA, USA installation

Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

ESA/eLISA the future of gravitational wave research

Financial support for the Advanced LIGO project was led by the NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council-OzGrav) making significant commitments and contributions to the project. Approximately 1,300 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration. A list of additional partners is available at https://my.ligo.org/census.php.

VIRGO Gravitational Wave interferometer, near Pisa, Italy

VIRGO Gravitational Wave interferometer, near Pisa, Italy

The Virgo Collaboration is currently composed of more than 500 scientists, engineers, and technicians from 99 institutes from Belgium, France, Germany, Hungary, Italy, the Netherlands, Poland, and Spain. The European Gravitational Observatory (EGO) hosts the Virgo detector near Pisa in Italy, and is funded by Centre National de la Recherche Scientifique (CNRS) in France, the Istituto Nazionale di Fisica Nucleare (INFN) in Italy, and Nikhef in the Netherlands. A list of the Virgo Collaboration members can be found at http://public.virgo-gw.eu/the-virgo-collaboration/. More information is available on the Virgo website at http://www.virgo-gw.eu.

See the full article here.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

The Max Planck Institute for Gravitational Physics (Albert Einstein Institute) is the largest research institute in the world specializing in general relativity and beyond. The institute is located in Potsdam and in Hannover where it is closely related to the Leibniz Universität Hannover.

From Nature (via SymmetryMag): “This black-hole collision just made gravitational waves even more interesting”

From Nature

20 April 2020
Davide Castelvecchi

An unprecedented signal from unevenly sized objects gives astronomers rare insight into how black holes spin.

A visualization of a collision between two differently sized black holes.Credit: N. Fischer, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes (SXS) Collaboration

Gravitational-wave astronomers have for the first time detected a collision between two black holes of substantially different masses — opening up a new vista on astrophysics and on the physics of gravity. The event offers the first unmistakable evidence from these faint space-time ripples that at least one black hole was spinning before merging, giving astronomers rare insight into a key property of these these dark objects.

“It’s an exceptional event,” said Maya Fishbach, an astrophysicist at the University of Chicago in Illinois. Similar mergers on which data have been published all took place between black holes with roughly equal masses, so this new one dramatically upsets that pattern, she says. The collision was detected last year, and was unveiled on 18 April by Fishbach and her collaborators at a virtual meeting of the American Physical Society, held entirely online because of the coronavirus pandemic.

The Laser Interferometer Gravitational-Wave Observatory (LIGO) — a pair of twin detectors based in Hanford, Washington, and Livingston, Louisiana — and the Virgo observatory near Pisa, Italy, both detected the event, identified as GW190412, with high confidence on 12 April 2019.

MIT /Caltech Advanced aLigo

VIRGO Gravitational Wave interferometer, near Pisa, Italy

The LIGO–Virgo collaboration, which includes Fishbach, posted its findings on the arXiv preprint server [https://arxiv.org/abs/2004.08342].

LIGO made the first discovery of gravitational waves in September 2015, detecting the space-time ripples from two merging black holes. LIGO, later joined by Virgo, subsequently made ten more detections in two observing runs that ended in 2017: nine more black-hole mergers and one collision of two neutron stars, which helped to explain the origin of the Universe’s heavy chemical elements.

The third and most recent run started on 1 April 2019 and ended on 27 March 2020, with a month-long break in October. Greatly improved sensitivity enabled the network to accumulate around 50 more ‘candidate events’ at a rate of roughly one per week. Until now, the international collaboration had unveiled only one other event from this observation period — a second merger between two neutron stars, dubbed GW190425, that was revealed in January.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Nature is a weekly international journal publishing the finest peer-reviewed research in all fields of science and technology on the basis of its originality, importance, interdisciplinary interest, timeliness, accessibility, elegance and surprising conclusions. Nature also provides rapid, authoritative, insightful and arresting news and interpretation of topical and coming trends affecting science, scientists and the wider public.

From AAS NOVA: “Learning from LIGO’s Second Binary Neutron Star Detection”

From AAS NOVA

20 March 2020
Susanna Kohler

LIGO has discovered another likely binary neutron star merger — and this one has new, interesting implications. [NASA/Goddard Space Flight Center]

In case you missed the news in January: the Laser Interferometer Gravitational-Wave Observatory (LIGO) has detected its second merger of two neutron stars — probably. In a recent publication, the collaboration details the interesting uncertainties and implications of this find.

MIT /Caltech Advanced aLigo

VIRGO Gravitational Wave interferometer, near Pisa, Italy

Artist’s illustration of a binary neutron star merger. [National Science Foundation/LIGO/Sonoma State University/A. Simonnet]

What We Saw and Why It’s Weird

On April 25, 2019, the LIGO detector in Livingston, Louisiana, spotted a gravitational-wave signal from a merger roughly 520 million light-years away. This single-detector observation — LIGO Hanford was offline at the time, and the Virgo detector in Europe didn’t spot it — was nonetheless strong enough to qualify as a definite detection of a merger.

Analysis of the GW190425 signal indicates that we saw the collision of a binary with a total mass of 3.3–3.7 times the mass of the Sun. While the estimated masses of the merging objects — between 1.1 and 2.5 solar masses — are consistent with the expected masses of neutron stars, that total mass measurement is much larger than any neutron star binary we’ve observed in our galaxy. We know of 17 galactic neutron star pairs with measured total masses, and these masses range from just 2.5 to 2.9 times that of the Sun. Why is GW190425 so heavy?

What It Suggests For Formation Channels

Blue and orange curves show the estimated total mass of GW190425 under different spin assumptions. In either case, the estimated mass is dramatically different from the total masses for the known galactic population of binary neutron stars, indicated with the grey histogram bars and the dashed line. [Abbott et al. 2020]

GW190425’s unusual mass may indicate that it formed differently from known galactic neutron star binaries.

Theory suggests that massive, fast-merging neutron-star pairs like GW190425 could potentially result from especially low-metallicity stars evolving in close binary systems. Under the right conditions, the energetic kicks caused by supernova explosions might be suppressed, allowing the objects to stay together in the close binary even after their evolution into neutron stars.

If this is the case, GW190425 could represent a population of binary neutron stars that we haven’t observed before. These binaries have remained invisible due to their ultra-tight orbits with sub-hour periods; the rapid accelerations of these objects would obscure their signals in pulsar surveys. The shortest-period neutron star binary we’ve detected with pulsar surveys has a period of 1.88 hours, and it won’t merge for another 46 million years. GW190425 could represent a very different binary neutron star population that’s just as common as the galactic population we know.

What If It’s Not Neutron Stars?

Unfortunately, the single-detector observation of GW190425 means we couldn’t pin down the gravitational-wave source’s location well — so follow-up observations haven’t yet spotted an electromagnetic counterpart like the one we had for GW170817, the first binary neutron star merger LIGO observed.

GW190425’s signal was localized to an unfortunately large area of ~16% of the sky, providing a challenge for electromagnetic and neutrino observatories hoping to discover counterparts. [Abbott et al. 2020]

This means we’re missing outside information confirming that this was a neutron star binary; it’s therefore possible that one or both of the merging objects was actually a black hole. If so, this would be smaller than any black holes we’ve detected so far, and we would need to significantly revamp our models of black hole binary formation.

There are clearly still a lot of open questions, but it’s early days yet! With the many recent upgrades to the LIGO and Virgo detectors, we can hope for more binary neutron star detections soon — and every new signal brings us a wealth of information in this rapidly developing field.

Citation

“GW190425: Observation of a Compact Binary Coalescence with Total Mass ~ 3.4 M⊙,” B. P. Abbott et al 2020 ApJL 892 L3.
https://iopscience.iop.org/article/10.3847/2041-8213/ab75f5

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

AAS Mission and Vision Statement

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009

From University of Waterloo: “Gravitational wave echoes may confirm Stephen Hawking’s hypothesis of quantum black holes”

From University of Waterloo

January 21, 2020

Echoes in gravitational wave signals suggest that the event horizon of a black hole may be more complicated than scientists currently think.

Gravitational waves Werner Benger-ZIB-AEI-CCT-LSU

Research from the University of Waterloo reports the first tentative detection of these echoes, caused by a microscopic quantum “fuzz” that surrounds newly formed black holes.

Gravitational waves are ripples in the fabric of space-time, caused by the collision of massive, compact objects in space, such as black holes or neutron stars.

“According to Einstein’s Theory of General Relativity, nothing can escape from the gravity of a black hole once it has passed a point of no return, known as the event horizon,” explained Niayesh Afshordi, a physics and astronomy professor at Waterloo. “This was scientists’ understanding for a long time, until Stephen Hawking used quantum mechanics to predict that quantum particles will slowly leak out of black holes, which we now call Hawking radiation.

Afshordi and his coauthor Jahed Abedi from Max-Planck-Institut für Gravitationsphysik in Germany, have reported the first tentative findings of these repeating echoes, providing experimental evidence that black holes may be radically different from what Einstein’s theory of relativity predicts, and lack event horizons.

They used gravitational wave data from the first observation of a neutron star collision, recorded by the LIGO/Virgo gravitational wave detectors.

MIT /Caltech Advanced aLigo

Localizations of gravitational-wave signals detected by LIGO in 2015 (GW150914, LVT151012, GW151226, GW170104), more recently, by the LIGO-Virgo network (GW170814, GW170817). After Virgo came online in August 2018

The echoes observed by Afshordi and Abedi match the simulated echoes predicted by models of black holes that account for the effects of quantum mechanics and Hawking radiation.

“Our results are still tentative because there is a very small chance that what we see is due to random noise in the detectors, but this chance becomes less likely as we find more examples,” said Afshordi. “Now that scientists know what we’re looking for, we can look for more examples, and have a much more robust confirmation of these signals. Such a confirmation would be the first direct probe of the quantum structure of space-time.”

The study Echoes from the Abyss: A highly spinning black hole remnant for the binary neutron star merger GW170817 was published in the Journal of Cosmology and Astroparticle Physics in November, and was awarded the first place Buchalter Cosmology Prize this month.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

In just half a century, the University of Waterloo, located at the heart of Canada’s technology hub, has become a leading comprehensive university with nearly 36,000 full- and part-time students in undergraduate and graduate programs.

Consistently ranked Canada’s most innovative university, Waterloo is home to advanced research and teaching in science and engineering, mathematics and computer science, health, environment, arts and social sciences. From quantum computing and nanotechnology to clinical psychology and health sciences research, Waterloo brings ideas and brilliant minds together, inspiring innovations with real impact today and in the future.

As home to the world’s largest post-secondary co-operative education program, Waterloo embraces its connections to the world and encourages enterprising partnerships in learning, research, and commercialization. With campuses and education centres on four continents, and academic partnerships spanning the globe, Waterloo is shaping the future of the planet.