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  • richardmitnick 7:13 am on July 21, 2019 Permalink | Reply
    Tags: "Where Do Supermassive Black Holes Come From?", , , , Caltech/MIT Advanced aLigo and Advanced VIRGO, , Gravitational wave astronomy, , , ,   

    From Western University, CA and WIRED: “Where Do Supermassive Black Holes Come From?” 

    From Western University Canada

    2
    Scott Woods, Western University, Illustration of supermassive black hole
    via

    WIRED

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    NASA

    June 28, 2019

    Researchers decipher the history of supermassive black holes in the early universe.

    At Western University
    MEDIA CONTACT:
    Jeff Renaud, Senior Media Relations Officer,
    519-661-2111, ext. 85165,
    519-520-7281 (mobile),
    jrenaud9@uwo.ca, @jeffrenaud99

    07.18.19
    From Wired
    Meredith Fore

    1
    NASA

    A pair of researchers at Western University in Ontario, Canada, developed their model by looking at quasars, which are supermassive black holes.

    Astronomers have a pretty good idea of how most black holes form: A massive star dies, and after it goes supernova, the remaining mass (if there’s enough of it) collapses under the force of its own gravity, leaving behind a black hole that’s between five and 50 times the mass of our Sun. What this tidy origin story fails to explain is where supermassive black holes, which range from 100,000 to tens of billions of times the mass of the Sun, come from. These monsters exist at the center of almost all galaxies in the universe, and some emerged only 690 million years after the Big Bang. In cosmic terms, that’s practically the blink of an eye—not nearly long enough for a star to be born, collapse into a black hole, and eat enough mass to become supermassive.

    One long-standing explanation for this mystery, known as the direct-collapse theory, hypothesizes that ancient black holes somehow got big without the benefit of a supernova stage. Now a pair of researchers at Western University in Ontario, Canada—Shantanu Basu and Arpan Das—have found some of the first solid observational evidence for the theory. As they described late last month in The Astrophysical Journal Letters, they did it by looking at quasars.

    Quasars are supermassive black holes that continuously suck in, or accrete, large amounts of matter; they get a special name because the stuff falling into them emits bright radiation, making them easier to observe than many other kinds of black holes. The distribution of their masses—how many are bigger, how many are smaller, and how many are in between—is the main indicator of how they formed.

    Astrophysicists at Western University have found evidence for the direct formation of black holes that do not need to emerge from a star remnant. The production of black holes in the early universe, formed in this manner, may provide scientists with an explanation for the presence of extremely massive black holes at a very early stage in the history of our universe.

    After analyzing that information, Basu and Das proposed that the supermassive black holes might have arisen from a chain reaction. They can’t say exactly where the seeds of the black holes came from in the first place, but they think they know what happened next. Each time one of the nascent black holes accreted matter, it would radiate energy, which would heat up neighboring gas clouds. A hot gas cloud collapses more easily than a cold one; with each big meal, the black hole would emit more energy, heating up other gas clouds, and so on. This fits the conclusions of several other astronomers, who believe that the population of supermassive black holes increased at an exponential rate in the universe’s infancy.

    “This is indirect observational evidence that black holes originate from direct-collapses and not from stellar remnants,” says Basu, an astronomy professor at Western who is internationally recognized as an expert in the early stages of star formation and protoplanetary disk evolution.

    Basu and Das developed the new mathematical model by calculating the mass function of supermassive black holes that form over a limited time period and undergo a rapid exponential growth of mass. The mass growth can be regulated by the Eddington limit that is set by a balance of radiation and gravitation forces or can even exceed it by a modest factor.

    “Supermassive black holes only had a short time period where they were able to grow fast and then at some point, because of all the radiation in the universe created by other black holes and stars, their production came to a halt,” explains Basu. “That’s the direct-collapse scenario.”

    But at some point, the chain reaction stopped. As more and more black holes—and stars and galaxies—were born and started radiating energy and light, the gas clouds evaporated. “The overall radiation field in the universe becomes too strong to allow such large amounts of gas to collapse directly,” Basu says. “And so the whole process comes to an end.” He and Das estimate that the chain reaction lasted about 150 million years.

    The generally accepted speed limit for black hole growth is called the Eddington rate, a balance between the outward force of radiation and the inward force of gravity. This speed limit can theoretically be exceeded if the matter is collapsing fast enough; the Basu and Das model suggests black holes were accreting matter at three times the Eddington rate for as long as the chain reaction was happening. For astronomers regularly dealing with numbers in the millions, billions, and trillions, three is quite modest.

    “If the numbers had turned out crazy, like you need 100 times the Eddington accretion rate, or the production period is 2 billion years, or 10 years,” Basu says, “then we’d probably have to conclude that the model is wrong.”

    There are many other theories for how direct-collapse black holes could be created: Perhaps halos of dark matter formed ultramassive quasi-stars that then collapsed, or dense clusters of regular mass stars merged and then collapsed.

    For Basu and Das, one strength of their model is that it doesn’t depend on how the giant seeds were created. “It’s not dependent on some person’s very specific scenario, specific chain of events happening in a certain way,” Basu says. “All this requires is that some very massive black holes did form in the early universe, and they formed in a chain reaction process, and it only lasted a brief time.”

    The ability to see a supermassive black hole forming is still out of reach; existing telescopes can’t look that far back yet. But that may change in the next decade as powerful new tools come online, including the James Webb Space Telescope, the Wide Field Infrared Survey Telescope, and the Laser Interferometer Space Antenna—all of which will hover in low Earth orbit—as well as the Large Synoptic Survey Telescope, based in Chile.

    NASA/ESA/CSA Webb Telescope annotated

    NASA/WFIRST

    Gravity is talking. Lisa will listen. Dialogos of Eide

    ESA/LISA Pathfinder

    ESA/NASA eLISA space based, the future of gravitational wave research

    LSST Camera, built at SLAC

    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    In the next five or 10 years, Basu adds, as the “mountain of data” comes in, models like his and his colleague’s will help astronomers interpret what they see.

    Avi Loeb, one of the pioneers of direct-collapse black hole theory and the director of the Black Hole Initiative at Harvard, is especially excited for the Laser Interferometer Space Antenna. Set to launch in the 2030s, it will allow scientists to measure gravitational waves—fine ripples in the fabric of space-time—more accurately than ever before.

    “We have already started the era of gravitational wave astronomy with stellar-mass black holes,” he says, referring to the black hole mergers detected by the ground-based Laser Interferometer Gravitational-Wave Observatory.

    Its space-based counterpart, Loeb anticipates, could provide a better “census” of the supermassive black hole population.

    For Basu, the question of how supermassive black holes are created is “one of the big chinks in the armor” of our current understanding of the universe. The new model “is a way of making everything work according to current observations,” he says. But Das remains open to any surprises delivered by the spate of new detectors—since surprises, after all, are often how science progresses.

    MIT /Caltech Advanced aLigo



    VIRGO Gravitational Wave interferometer, near Pisa, Italy


    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


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

    LSC LIGO Scientific Collaboration


    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

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

    Gravity is talking. Lisa will listen. Dialogos of Eide

    ESA/eLISA the future of gravitational wave research

    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


    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    See the full WIRED article here .
    See the full Western University article here .

    The University of Western Ontario (UWO), corporately branded as Western University as of 2012 and commonly shortened to Western, is a public research university in London, Ontario, Canada. The main campus is on 455 hectares (1,120 acres) of land, surrounded by residential neighbourhoods and the Thames River bisecting the campus’s eastern portion. The university operates twelve academic faculties and schools. It is a member of the U15, a group of research-intensive universities in Canada.

    The university was founded on 7 March 1878 by Bishop Isaac Hellmuth of the Anglican Diocese of Huron as the Western University of London, Ontario. It incorporated Huron University College, which had been founded in 1863. The first four faculties were Arts, Divinity, Law and Medicine. The Western University of London became non-denominational in 1908. Beginning in 1919, the university has affiliated with several denominational colleges. The university grew substantially in the post-World War II era, as a number of faculties and schools were added to university.

    Western is a co-educational university, with more than 24,000 students, and with over 306,000 living alumni worldwide. Notable alumni include government officials, academics, business leaders, Nobel Laureates, Rhodes Scholars, and distinguished fellows. Western’s varsity teams, known as the Western Mustangs, compete in the Ontario University Athletics conference of U Sports.

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    See the full article here .

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  • richardmitnick 2:35 pm on July 10, 2019 Permalink | Reply
    Tags: , , , , , Gravitational wave astronomy, ,   

    From Princeton University: “Princeton scientists spot two supermassive black holes on collision course with each other” 

    Princeton University
    From Princeton University

    1
    Titanic Twosome: A Princeton-led team of astrophysicists has spotted a pair of supermassive black holes, roughly 2.5 billion light-years away, that are on a collision course (inset). The duo can be used to estimate how many detectable supermassive black hole mergers are in the present-day universe and to predict when the historic first detection of the background “hum” of gravitational waves will be made.
    Image courtesy of Andy Goulding et al./Astrophysical Journal Letters 2019

    July 10, 2019

    Each black hole’s mass is more than 800 million times that of our sun. As the two gradually draw closer together in a death spiral, they will begin sending gravitational waves rippling through space-time.


    Two Black Holes Merge into One.
    LIGO Lab Caltech : MIT
    Published on Feb 11, 2016
    A computer simulation shows the collision of two black holes, a tremendously powerful event detected for the first time ever by the Laser Interferometer Gravitational-Wave Observatory, or LIGO. LIGO detected gravitational waves, or ripples in space and time generated as the black holes spiraled in toward each other, collided, and merged. This simulation shows how the merger would appear to our eyes if we could somehow travel in a spaceship for a closer look. It was created by solving equations from Albert Einstein’s general theory of relativity using the LIGO data.

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    The two merging black holes are each roughly 30 times the mass of the sun, with one slightly larger than the other. Time has been slowed down by a factor of about 100. The event took place 1.3 billion years ago.

    The stars appear warped due to the incredibly strong gravity of the black holes. The black holes warp space and time, and this causes light from the stars to curve around the black holes in a process called gravitational lensing. The ring around the black holes, known as an Einstein ring, arises from the light of all the stars in a small region behind the holes, where gravitational lensing has smeared their images into a ring.

    The gravitational waves themselves would not be seen by a human near the black holes and so do not show in this video, with one important exception. The gravitational waves that are traveling outward toward the small region behind the black holes disturb that region’s stellar images in the Einstein ring, causing them to slosh around, even long after the collision. The gravitational waves traveling in other directions cause weaker, and shorter-lived sloshing, everywhere outside the ring.

    Those cosmic ripples will join the as-yet-undetected background noise of gravitational waves from other supermassive black holes. Even before the destined collision, the gravitational waves emanating from the supermassive black hole pair will dwarf those previously detected from the mergers of much smaller black holes and neutron stars.

    “Collisions between enormous galaxies create some of the most extreme environments we know of, and should theoretically culminate in the meeting of two supermassive black holes, so it was incredibly exciting to find such an immensely energetic pair of black holes so close together in our Hubble Space Telescope images,” said Andy Goulding, an associate research scholar in astrophysical sciences at Princeton who is the lead author on a paper appearing July 10 in Astrophysical Journal Letters.

    “Supermassive black hole binaries produce the loudest gravitational waves in the universe,” said co-discoverer and co-author Chiara Mingarelli, an associate research scientist at the Flatiron Institute’s Center for Computational Astrophysics in New York City. Gravitational waves from supermassive black hole pairs “are a million times louder than those detected by LIGO.

    .”

    “When these supermassive black holes merge, they will create a black hole hundreds of times larger than the one at the center of our own galaxy,” said Princeton graduate student Kris Pardo, a co-author on the paper.

    The two supermassive black holes are especially interesting because they are around 2.5 billion light-years away from Earth. Since looking at distant objects in astronomy is like looking back in time, the pair belong to a universe 2.5 billion years younger than our own. Coincidentally, that’s roughly the same amount of time the astronomers estimate the black holes will take to begin producing powerful gravitational waves.

    In the present-day universe, the black holes are already emitting these gravitational waves, but even at light speed the waves won’t reach us for billions of years. The duo is still useful, though. Their discovery can help scientists estimate how many nearby supermassive black holes are emitting gravitational waves that we could detect right now.

    Detecting the gravitational wave background would help answer some of the biggest unknowns in astronomy, such as how often galaxies merge and whether supermassive black hole pairs merge at all, or if they become stuck in a near-endless waltz around each other.

    “It’s a major embarrassment for astronomy that we don’t know if supermassive black holes merge,” said Jenny Greene, a professor of astrophysical sciences at Princeton and a co-author on the paper. “For everyone in black hole physics, observationally this is a long-standing puzzle that we need to solve.”

    Supermassive black holes can contain millions or even billions of suns’ worth of mass. Nearly all galaxies, including our own Milky Way, contain at least one of these behemoths at their core.

    SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory


    SGR A and SGR A* from Penn State and NASA/Chandra

    When galaxies merge, their supermassive black holes meet up and begin orbiting one another. Over time, this orbit tightens as gas and stars pass between the black holes and steal energy.

    Once the supermassive black holes get too close, though, this energy theft all but stops. Some theories suggest that they stall at around 1 parsec apart (roughly 3.2 light-years). This slowdown lasts nearly indefinitely and is known as the “final parsec problem.” In this scenario, only very rare groups of three or more supermassive black holes result in mergers.

    Astronomers can’t just look for stalled pairs, because long before the black holes are a parsec apart, they’re too close to distinguish as two separate objects. Moreover, they don’t produce strong gravitational waves until they overcome the final parsec hurdle and get closer together. (Observed as they were 2.5 billion years ago, the newfound supermassive black holes appear about 430 parsecs apart.)

    If the final parsec problem turns out not to be a problem, then astronomers expect that the universe is filled with the clamor of gravitational waves from supermassive black hole pairs in the process of merging. “This noise is called the gravitational wave background, and it’s a bit like a chaotic chorus of crickets chirping in the night,” Goulding said. “You can’t discern one cricket from another, but the volume of the noise helps you estimate how many crickets are out there.”

    If two supermassive black holes do collide and combine, it will send a thundering “chirp” that will dwarf the background chorus – but it’s no small task to “hear” it.

    The telltale gravitational waves generated by merging supermassive black holes are outside the frequencies currently observable by experiments such as LIGO and Virgo, which have detected the mergers of much smaller black holes and neutron stars. Scientists hunting for the larger gravitational waves from supermassive black hole collisions rely on arrays of special stars called pulsars that act like metronomes, sending out radio waves in a steady rhythm. If a passing gravitational wave stretches or compresses the space between Earth and the pulsar, the rhythm will be thrown off slightly.

    Detecting the gravitational wave background using one of these pulsar timing arrays takes patience and plenty of monitored stars. A single pulsar’s rhythm might be disrupted by only a few hundred nanoseconds over a decade. The louder the background noise, the larger the timing disruptions and the quicker the detection will be made.

    Goulding, Greene and the other observational astronomers on the team detected the two titans with the Hubble Space Telescope. Although supermassive black holes aren’t directly visible through an optical telescope like Hubble, they are surrounded by bright clumps of luminous stars and warm gas drawn in by the powerful gravitational tug.

    Stars around SGR A* including S0-2 Andrea Ghez Keck/UCLA Galactic Center Group.

    For its time in history, the galaxy harboring the newfound supermassive black hole pair “is basically the most luminous galaxy in the universe,” Goulding said. What’s more, the galaxy’s core is shooting out two unusually colossal plumes of gas. When they pointed Hubble at it to uncover the origins of its spectacular gas clouds, the researchers discovered that the system contained not one but two massive black holes.

    The observational astronomers then teamed up with gravitational wave physicists Mingarelli and Pardo to interpret the finding in the context of the gravitational wave background. The discovery provides an anchor point for estimating how many merging supermassive black holes are within detection distance of Earth. Previous estimates relied on computer models of how often galaxies merge, rather than actual observations of supermassive black hole pairs.

    Based on the data, Pardo and Mingarelli predicted that in an optimistic scenario, there are about 112 nearby supermassive black holes emitting gravitational waves. The first detection of the gravitational wave background from supermassive black hole mergers should therefore come within the next five years or so. If such a detection isn’t made, that would be evidence that the final parsec problem may be insurmountable. The team is currently looking at other galaxies similar to the one harboring the newfound supermassive black hole binary. Finding additional pairs will help them further hone their predictions.

    “This is the first example of a close pair of such massive black holes that we’ve found, but there may well be additional binary black holes remaining to be discovered,” said co-author Professor Michael Strauss, the associate chair of Princeton’s Department of Astrophysical Sciences. “The more we can learn about the population of merging black holes, the better we will understand the process of galaxy formation and the nature of the gravitational wave background.”

    See the full article here .

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    Princeton University Campus

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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  • richardmitnick 8:33 am on May 25, 2019 Permalink | Reply
    Tags: , , , , , , , Gravitational wave astronomy,   

    From European Space Agency: “Two merging black holes” 

    ESA Space For Europe Banner

    From European Space Agency

    1

    20/05/2019

    Black holes are among the most fascinating objects in the Universe. Enclosing huge amounts of mass in relatively small regions, these compact objects have enormous densities that give rise to some of the strongest gravitational fields in the cosmos, so strong that nothing can escape – not even light.

    This artistic impression shows two black holes that are spiralling towards each other and will eventually coalesce. A black hole merger was first detected in 2015 by LIGO, the Laser Interferometer Gravitational-Wave Observatory, which detected the gravitational waves – fluctuations in the fabric of spacetime – created by the giant collision.

    Black holes and gravitational waves are both predictions of Albert Einstein’s general relativity, which was presented in 1915 and remains to date the best theory to describe gravity across the Universe.

    Karl Schwarzschild derived the equations for black holes in 1916, but they remained rather a theoretical curiosity for several decades, until X-ray observations performed with space telescopes could finally probe the highly energetic emission from matter in the vicinity of these extreme objects. The first ever image of a black hole’s dark silhouette, cast against the light from matter in its immediate surrounding, was only captured recently by the Event Horizon Telescope and published just last month.

    As for gravitational waves, it was Einstein himself who predicted their existence from his theory, also in 1916, but it would take another century to finally observe these fluctuations. Since 2015, the ground-based LIGO and Virgo observatories have assembled over a dozen detections, and gravitational-wave astronomy is a burgeoning new field of research.

    But another of Einstein’s predictions found observational proof much sooner: the gravitational bending of light, which was demonstrated only a few years after the theory had appeared, during a total eclipse of the Sun in 1919.

    In the framework of general relativity, any object with mass bends the fabric of spacetime, deflecting the path of anything that passes nearby – including light. An artistic view of this distortion, also known as gravitational lensing, is depicted in this representation of two merging black holes.

    One hundred years ago, astronomers set out to test general relativity, observing whether and by how much the mass of the Sun deflects the light of distant stars. This experiment could only be performed by obscuring the Sun’s light to reveal the stars around it, something that is possible during a total solar eclipse.

    On 29 May 1919, Sir Arthur Eddington observed the distant stars around the Sun during an eclipse from the island of Príncipe, in West Africa, while Andrew Crommelin performed similar observations in Sobral, in the north east of Brazil.

    Eddington/Einstein exibition of gravitational lensing solar eclipse of 29 May 1919

    The results, presented six months later, indicated that stars observed near the solar disc during the eclipse were slightly displaced, with respect to their normal position in the sky, roughly by the amount predicted by Einstein’s theory for the Sun’s mass to have deflected their light.

    “Lights All Askew in the Heavens,” headlined the New York Times in November 1919 to announce the triumph of Einstein’s new theory. This inaugurated a century of exciting experiments investigating gravity on Earth and in space, proving general relativity more and more precisely.

    We have made giant leaps over the past hundred years, but there is still much for us to discover. Athena, ESA’s future X-ray observatory, will investigate in unprecedented detail the supermassive black holes that sit at the centre of galaxies.


    LISA, another future ESA mission, will detect gravitational waves from orbit, looking for the low-frequency fluctuations that are released when two supermassive black holes merge and can only be detected from space.

    ESA/NASA eLISA

    ESA/NASA eLISA space based, the future of gravitational wave research

    Both missions are currently in the study phase, and are scheduled to launch in the early 2030s. If Athena and LISA could operate jointly for at least a few years, they could perform a unique experiment: observing the merger of supermassive black holes both in gravitational waves and X-rays, using an approach known as multi-messenger astronomy.

    We have never observed such a merger before: we need LISA to detect the gravitational waves and tell us where to look in the sky, then we need Athena to observe it with high precision in X-rays to see how the mighty collision affects the gas surrounding the black holes. We don’t know what happens during such a cosmic clash so this experiment, much like the eclipse of 1919 that first proved Einstein’s theory, is set to shake our understanding of gravity and the Universe.

    See the full article here .


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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 9:49 am on May 8, 2019 Permalink | Reply
    Tags: , , , , , , , Gravitational wave astronomy, , , Persistent gravitational wave observables, , When two massive objects such as neutron stars or black holes collide they send shockwaves through the Universe rippling the very fabric of space-time itself.   

    From Cornell University via Science Alert: “Gravitational Waves Could Be Leaving Some Weird Lasting Effects in Their Wake” 


    From Cornell University

    via

    ScienceAlert

    Science Alert

    8 MAY 2019
    MICHELLE STARR

    1
    (Henze/NASA)

    The faint, flickering distortions of space-time we call gravitational waves are tricky to detect, and we’ve only managed to do so in recent years. But now scientists have calculated that these waves may leave more persistent traces of their passing – traces we may also be able to detect.

    Such traces are called ‘persistent gravitational wave observables’, and in a new paper [Physical Review D], an international team of researchers [see paper for science team authors] has refined the mathematical framework for defining them. In the process, they give three examples of what these observables could be.

    Here’s the quick lowdown on gravitational waves: When two massive objects such as neutron stars or black holes collide, they send shockwaves through the Universe, rippling the very fabric of space-time itself. This effect was predicted by Einstein in his theory of general relativity in 1916, but it wasn’t until 2015 that we finally had equipment sensitive enough to detect the ripples.

    That equipment is an interferometer that shoots two or more laser beams down arms that are several kilometres in length. The wavelengths of these laser beams interfere to cancel each other out, so, normally, no light hits the instrument’s photodetectors.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy


    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

    Gravity is talking. Lisa will listen. Dialogos of Eide

    ESA/eLISA the future of gravitational wave research

    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


    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    But when a gravitational wave hits, the warping of space-time causes these laser beams to oscillate, shrinking and stretching. This means that their interference pattern is disrupted, and they no longer cancel each other out – so the laser hits the photodetector. The pattern of the light that hits can tell scientists about the event that created the wave.

    But that shrinking and stretching and warping of space-time, according to astrophysicist Éanna Flanagan of Cornell University and colleagues, could be having a much longer-lasting effect.

    As the ripples in space-time propagate, they can change the velocity, acceleration, trajectories and relative positions of objects and particles in their way – and these features don’t immediately return to normal afterwards, making them potentially observable.

    Particles, for instance, disturbed by a burst of gravitational waves, could show changes. In their new framework, the research team mathematically detailed changes that could occur in the rotation rate of a spinning particle, as well as its acceleration and velocity.

    Another of these persistent gravitational wave observables involves a similar effect to time dilation, whereby a strong gravitational field slows time.

    Because gravitational waves warp both space and time, two extremely precise and synchronised clocks in different locations, such as atomic clocks, could be affected by gravitational waves, showing different times after the waves have passed.

    Finally, the gravitational waves could actually permanently shift the relative positions in the mirrors of a gravitational wave interferometer – not by much, but enough to be detectable.

    Between its first detection in 2015 and last year, the LIGO-Virgo gravitational wave collaboration detected a handful of events before LIGO was taken offline for upgrades.

    At the moment, there are not enough detections in the bank for a meaningful statistical database to test these observables.

    But LIGO-Virgo was switched back on on 1 April, and since then has been detecting at least one gravitational wave event per week.

    The field of gravitational wave astronomy is heating up, space scientists are itching to test new mathematical calculations and frameworks, and it won’t be long before we’re positively swimming in data.

    This is just such an incredibly exciting time for space science, it really is.

    See the full article here .

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    Once called “the first American university” by educational historian Frederick Rudolph, Cornell University represents a distinctive mix of eminent scholarship and democratic ideals. Adding practical subjects to the classics and admitting qualified students regardless of nationality, race, social circumstance, gender, or religion was quite a departure when Cornell was founded in 1865.

    Today’s Cornell reflects this heritage of egalitarian excellence. It is home to the nation’s first colleges devoted to hotel administration, industrial and labor relations, and veterinary medicine. Both a private university and the land-grant institution of New York State, Cornell University is the most educationally diverse member of the Ivy League.

    On the Ithaca campus alone nearly 20,000 students representing every state and 120 countries choose from among 4,000 courses in 11 undergraduate, graduate, and professional schools. Many undergraduates participate in a wide range of interdisciplinary programs, play meaningful roles in original research, and study in Cornell programs in Washington, New York City, and the world over.

     
  • richardmitnick 3:39 pm on May 6, 2019 Permalink | Reply
    Tags: , , , , Gravitational wave astronomy, ,   

    From Science News: “LIGO [and VIRGO] on the lookout for these 8 sources of gravitational waves” 

    From Science News

    May 6, 2019
    Lisa Grossman

    Astronomers still hope to catch a star going supernova and a bumpy neutron star, among others.

    1
    BANG, CRASH Physicists using the LIGO and Virgo observatories are catching all sorts of cosmic collisions, including of pairs of neutron stars (illustrated). But scientists hope to bag even more exotic quarry. NASA’s Goddard Space Flight Center/CI Lab

    Seekers of gravitational waves are on a cosmic scavenger hunt.

    Since the Advanced Laser Interferometer Gravitational-wave Observatory turned on in 2015, physicists have caught these ripples in spacetime from several exotic gravitational beasts — and scientists want more.

    This week, LIGO and its partner observatory Virgo announced five new possible gravitational wave detections in a single month, making what was once a decades-long goal almost commonplace (SN Online: 5/2/19).

    _____________________________________________________
    Picking up

    In just one month, scientists have already spotted 5 possible gravitational wave events, plotted here as a function of their approximate distance from Earth. That’s compared to 11 events from all previous observations combined. Most detections are from merging black holes, but neutron star mergers (red) are also in the mix. And one event (yellow) might be a mash up between a black hole and a neutron star.

    Gravitational wave detections by LIGO and Virgo are becoming more frequent

    4
    E. Otwell, T. Tibbitts

    _____________________________________________________

    “We’re just beginning to see the field of gravitational wave astronomy open,” LIGO spokesperson Patrick Brady from the University of Wisconsin–Milwaukee said May 2 in a news conference. “Opening up a new window on the universe like this will hopefully bring us a whole new perspective on what’s out there.”

    The speed and pitch of gravitational wave signals allow astronomers to make out what’s stirring up the waves. Here are the sources of gravitational waves that scientists that already have in their nets, and what they’re still hoping to find.
    1. Pairs of colliding black holes

    Status: Found

    7
    SWEET SUCCESS For the first time, physicists have directly observed gravitational waves, caused by two black holes colliding (illustrated here). SXS collaboration.

    2. Pairs of colliding neutron stars

    Status: Found

    3. A neutron star crashing into a black hole

    Status: Maybe

    3
    TOUGH STUFF An exotic substance thought to exist within a type of collapsed star called a neutron star (illustrated) may be stronger than any other known material.
    Casey Reed/Penn State University, Wikimedia Commons

    4. A collision involving an intermediate-mass black hole

    Status: Not yet

    9
    HIDDEN FIGURE An intermediate-mass black hole about 2,200 times as heavy as the sun may lurk at the center of this dense ball of stars, a globular cluster called 47 Tucanae.
    NASA, ESA, Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, J. Mack/STScI, G. Piotto/University of Padua

    5. A bumpy neutron star

    Status: Not yet

    6. Supernova explosions

    Status: Not yet

    LIGO and Virgo might also be able to pick up gravitational waves from supernova explosions, the bright cataclysms at the end of massive stars’ lives.

    6
    SHINE BRIGHT Supernova 1987A shone as a brilliant point of light near the Tarantula Nebula (pink cloud) in the Large Magellanic Cloud, as pictured from an observatory in Chile.

    Supernovas emit many types of light and particles, including ghostly subatomic particles called neutrinos that are born deep in the heart of the explosions (SN: 2/18/17, p. 20). But scientists still don’t know exactly what makes a star explode as a supernova in the first place.

    What they do know is that during a supernova explosion, the central core of the star collapses, and the resulting proto-neutron star gathers material from the remainder of the collapsing core. The turbulence at the surface of the proto-neutron star makes it vibrate like a bell, sending off gravitational waves. That specific gravitational wave signal is strongly related to the strength of the turbulence and the structure of the nascent neutron star, astrophysicist David Radice of Princeton University and colleagues report April 29 in the Astrophysical Journal Letters.

    7. Waves triggered by the Big Bang

    Status: Not yet

    8. New sources?

    Status: Not yet

    LIGO Caltech. LIGO and Virgo detect neutron star smash-ups. May 2, 2019.
    See https://sciencesprings.wordpress.com/2019/05/06/from-mit-caltech-advanced-aligo-ligo-and-virgo-detect-neutron-star-smash-ups/

    See the full article here .


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  • richardmitnick 9:49 am on May 4, 2019 Permalink | Reply
    Tags: , , , , , , Gravitational wave astronomy, ,   

    From MIT News: “3 Questions: Salvatore Vitale on LIGO’s latest detections” 

    MIT News
    MIT Widget

    From MIT News

    May 2, 2019
    Jennifer Chu

    1
    Salvatore Vitale, assistant professor of physics at MIT and member of the LIGO Scientific Collaboration. Courtesy of MIT Kavli Institute for Astrophysics and Space Research.

    Kavli MIT Institute of Astrophysics and Space Research

    “We will keep listening for these faint and remote cosmic whispers,” says the physics professor.

    It’s been just three weeks since LIGO resumed its hunt for cosmic ripples through space-time, and already the gravitational-wave hunter is off to a running start.

    One of the detections researchers are now poring over is a binary neutron star merger — a collision of two incredibly dense stars, nearly 500 million light years away. The power of this stellar impact set off gravitational waves across the cosmos, eventually reaching Earth as infinitely small ripples that were picked up by LIGO (the Laser Interferometer Gravitational-wave Observatory, operated jointly by Caltech and MIT), as well as by Virgo, LIGO’s counterpart in Italy, on April 25 at 4 a.m. ET.



    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

    Researchers have determined that the source of the gravitational wave signal is likely a binary neutron star merger, which they’ve dubbed #S190425z. This is the second time that LIGO has discovered such a source.

    The other neutron star merger, detected in 2017, was also the first event captured by LIGO that was also observed using optical telescopes. As astronomers around the world pointed telescopes at this first neutron star merger, they were able to see the brilliant “kilonova” explosion generated as the two stars merged. They also detected signatures of gold and platinum in the aftermath — direct evidence for how heavy elements are produced in the universe.

    With LIGO’s new detection, astronomers are again pointing telescopes to the skies and searching for optical traces of the stellar merger and any resulting cosmic goldmine.

    MIT News caught up with Salvatore Vitale, assistant professor of physics at MIT and a member of the LIGO Scientific Collaboration, about this newest stellar discovery and hints of even more “cosmic whispers” on the horizon — including the tantalizing possibility that LIGO has also captured the collision of a black hole and a neutron star.

    Q: Walk us through the moment of discovery. When did this signal come in, and what told you that it was likely a binary neutron star merger?

    A: The signal hit Earth at 4:18 a.m. EDT. Unfortunately, at that time the LIGO detector in Hanford, Washington, was not collecting data. The signal was thus detected by the LIGO instrument in Baton Rouge, Louisiana, and the Virgo detector in Italy.

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

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Having only two detectors online did not affect our confidence of it being real, since neutron star binaries spend more than one minute in our detectors and these kinds of very long chirps cannot easily be confused with instrumental artifacts or other sources of noise. Similarly, we were able to measure extremely well the mass of the source, which told us it was a binary neutron star, the second ever detected by LIGO and Virgo.

    The main consequence of only having two detectors online was that it hurt our ability to localize the source in the sky. The sky map we sent out had a very large uncertainty, over 10,000 square degrees, which is a huge area to follow up, if you are looking for an electromagnetic counterpart.

    Q: Since the notice from LIGO went out, astronomers have been training telescopes on the sky. What have they been able to find about this new merger, and how is it different from the one LIGO detected in 2017?

    A: When two neutron stars smash one against the other, they trigger a cataclysmic explosion that releases huge amounts of energy and creates some of the heaviest elements in the universe (gold, among others). Finding both gravitational and electromagnetic waves can tell us about the environment in which these systems form, how they shine, their role in enriching galaxies with metals, and about the universe. This is why we routinely and automatically send public alerts to astronomers, so that they can try to identify the sources of our gravitational-wave events.

    This is challenging for S190425z, since it has been localized poorly (compare 10,000 square degrees for S190425z with 30 square degrees for the first binary neutron star merger, GW170817). Another important difference is that S190425z was nearly four times further away. Both these factors make it harder to successfully find an electromagnetic counterpart to S190425z. You want to scan a much larger area, and you want to find a weaker and more distant source. This doesn’t mean that astronomers are not trying hard! In fact, in the last 36 hours there have been dozens of observations. So far nothing too convincing, but a lot of excitement! It is nice to see the broader community so engaged with the follow-up of LIGO and Virgo’s events.

    Q: Since it started its newest observing run, LIGO has been detecting at least one gravitational wave source per week. What does this say about what sort of extreme phenomena are happening in the universe, on a daily basis?

    A: The last few weeks have been incredibly exciting! So far we are making discoveries at roughly the rate we were expecting: one binary black hole a week and one binary neutron star a month. This confirms our expectations that gravitational waves can really play a major role in understanding the most extreme objects of the universe.

    It also says that it is not uncommon that two stellar-mass black holes merge, which was not obvious at all before LIGO and Virgo discovered them. We still don’t know if the black holes pairs we are seeing had been together their whole cosmic life, first as normal stars, then as black holes, or if instead they were born separately and then just happened to meet and form a binary system. Both avenues are possible, and with a few more tens of detections we should be able to tell which of these two scenarios happens more often.

    Then there is always the possibility of detecting something new and unexpected! As I started drafting these answers, we detected #S190426c, which, if of astrophysical origin, could be the first neutron star colliding into a black hole ever detected by humans. We will know more in the next few weeks, and we will keep listening for these faint and remote cosmic whispers.

    See the full article here .


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  • richardmitnick 8:12 am on May 3, 2019 Permalink | Reply
    Tags: "Have scientists observed a black hole swallowing a neutron star?", , , , , , , Gravitational wave astronomy, ,   

    From Cardiff University: “Have scientists observed a black hole swallowing a neutron star?” 

    Cardiff University

    From Cardiff University

    3 May 2019

    Professor Mark Hannam
    Head of Gravitational Physics Group
    Director of the Gravity Exploration Institute

    1
    Now iconic image NSF/LIGO/Sonoma State University/A. Simonnet

    Within weeks of switching their machines back on to scour the sky for more sources of gravitational waves, scientists are poring over data in an attempt to further understand an unprecedented cosmic event.

    Astronomers working at the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the European-based Virgo detector have reported the possible detection of gravitational waves emanating from the collision of a neutron star and a black hole.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy


    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

    Gravity is talking. Lisa will listen. Dialogos of Eide

    ESA/eLISA the future of gravitational wave research

    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


    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    The signal, detected on 26 April, came just weeks after the teams turned the updated detectors back on to start their third observation run, named “O3”.

    “The universe is keeping us on our toes,” says Patrick Brady, spokesperson for the LIGO Scientific Collaboration and a professor of physics at the University of Wisconsin-Milwaukee. “We’re especially curious about the April 26 candidate. Unfortunately, the signal is rather weak. It’s like listening to somebody whisper a word in a busy café; it can be difficult to make out the word or even to be sure that the person whispered at all. It will take some time to reach a conclusion about this candidate.”

    The possible detection not only throws light on an event that up until now has never been observed, but also confirms the unprecedented accuracy with which the gravitational wave detectors are now operating.

    Included in the latest batch of discoveries is another possible merger between two neutron stars – potentially the second time this has been observed by the LIGO and Virgo teams – as well as a further three interesting black hole mergers.

    Professor Mark Hannam, a member of the LIGO team and Director of Cardiff University’s Gravity Exploration Institute said: “Yet again the LIGO and Virgo detectors have surpassed expectations. Our most optimistic estimates were for a detection every week, and the first month of the run gave us five candidates.”

    Dr Vivien Raymond, from Cardiff University’s Gravity Exploration Institute, said: “LIGO-Virgo’s third observing run has already proven to be more interesting than we expected, barely a month after it started. It’s exciting to think about the next surprises in the Universe for us to discover.”

    Gravitational waves are ripples in space produced by massive cosmic events such as the collision of black holes or the explosion of supernovae.

    Research undertaken by Cardiff University’s Gravity Exploration Institute has laid the foundations for how we go about detecting gravitational waves with the development of novel algorithms and software that have now become standard tools for detecting the elusive signals.

    The Institute also includes world-leading experts in the collision of black holes, who have produced large-scale computer simulations of what is to be expected and observed when these violent events occur, as well as experts in the design of gravitational-wave detectors.

    The twin detectors of LIGO—one in Washington and one in Louisiana—along with Virgo, located at the European Gravitational Observatory (EGO) in Italy, resumed operations on 1 April , after undergoing a series of upgrades to increase their sensitivities to gravitational waves—ripples in space and time.

    Each detector now surveys larger volumes of the universe than before, searching for extreme events such as smash-ups between black holes and neutron stars.

    In total, since making history with the first-ever direct detection of gravitational waves in 2015, the network has spotted evidence for two neutron star mergers; 13 black hole mergers; and one possible black hole-neutron star merger.

    See the full article here .


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    Cardiff Unversity is an ambitious and innovative university with a bold and strategic vision located in a beautiful and thriving capital city. Our research is world-leading and we provide an educationally outstanding experience for our students.

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  • richardmitnick 2:02 pm on May 1, 2019 Permalink | Reply
    Tags: , , , , , Gravitational wave astronomy, , , QRPN-quantum radiation pressure noise   

    From MIT News: “Quantum measurement could improve gravitational wave detection sensitivity” 

    MIT News
    MIT Widget

    From MIT News

    May 1, 2019
    Brittany Flaherty | School of Science

    Research could enable a new suite of experiments to measure quantum activity at room temperature.

    1
    New technology allows LIGO researchers to model noise from quantum phenomena at room temperature. The green path shows the optical fiber that carries light into the chamber, and the red path shows where the light exits.

    Minutes before dawn on Sept. 14, 2015, the Laser Interferometer Gravitational-wave Observatory (LIGO) became the first-ever instrument on Earth to directly detect a gravitational wave. This work, led by the LIGO Scientific Collaboration with prominent roles from MIT and Caltech, was the first confirmation of this consequence of Albert Einstein’s theory of general relativity — 100 years after he first predicted it. The groundbreaking detection represented an enormous step forward in the field of astrophysics. In the years since, scientists have striven to achieve even greater sensitivity in the LIGO detectors.

    New research has taken investigators one step closer to this goal. Nergis Mavalvala, the Curtis and Kathleen Marble Professor of Astrophysics at MIT, postdoc Robert Lanza, graduate student Nancy Aggarwal, and their collaborators at Louisiana State University (LSU) recently conducted experiments that could help overcome a future limitation in Advanced LIGO. In their laboratory study, the team successfully measured a type of noise that will soon hold the LIGO instruments back from detecting gravitational waves with greater sensitivity.

    Their study, reported recently in Nature, was the first to measure an important source of quantum noise at room temperature and at frequencies relevant to gravitational wave detectors. Funded by the National Science Foundation, this work could enable researchers to understand this limiting noise source and test ideas for circumventing it to further increase LIGO’s sensitivity to gravitational waves.

    In addition to future applications for improving LIGO’s detection abilities, Mavalvala says these observations of quantum effects at room temperature could help scientists learn more about how quantum mechanics can disturb the precision of measurements generally — and how best to get around these quantum noise limits.

    “This result was important for the gravitational wave community,” says Mavalvala. “But more broadly, this is essentially a room-temperature quantum resource, and that’s something that many communities should care about.”

    Sensitivity upgrade

    LIGO has undergone upgrades since its first gravitational wave searches in 2002; the currently operating version of the instrumentation is called Advanced LIGO following major upgrades in 2015. But to get LIGO to its maximum design sensitivity, Mavalvala says her team needs to be able to conduct experiments and test improvement strategies in the laboratory rather than on the LIGO instruments themselves. LIGO’s astrophysical detection work is too important to interfere with, so she and her collaborators have developed instruments in the lab that can mimic the sensitivity of the real thing. In this case, the team aimed to reproduce processes that occur in LIGO to measure a type of noise called quantum radiation pressure noise (QRPN).

    In LIGO, gravitational waves are detected by using lasers to probe the motion of mirrors. The mirrors are suspended as pendulums, allowing them to have periodic motion similar to a mass on a spring. When laser beams hit the movable mirrors, the momentum carried by the light applies pressure on the mirror and causes them to move slightly.

    “I like to think of it like a pool table,” says Aggarwal. “When your white cue ball strikes the ball in front of it, the cue ball comes back but it still moves the other ball. When a photon that was traveling forward then travels backwards, the momentum went somewhere; [in this case] that momentum went into the mirror.”

    The quantum nature of light, which is made up of photons, dictates that there are quantum fluctuations in the number of photons hitting the mirrors, creating an uncertain amount of force on the mirrors at any given moment. This uncertainty results in random perturbations of the mirror. When the laser power is high enough, this QRPN can interfere with gravitational wave detection. At Advanced LIGO’s full design sensitivity, with many hundreds of kilowatts of laser power hitting 40-kilogram mirrors, QRPN will become a dominant limitation.

    Minuscule mirrors

    To address this imminent issue, Mavalvala, Aggarwal, and their collaborators designed an experiment to recreate the effects of QRPN in a laboratory setting. One challenge was that the team could not use lasers as powerful as those in Advanced LIGO in their lab experiments. The greater the laser power and the lighter the mass of the mirror oscillator, the stronger the radiation pressure-driven motion. To be able to detect this motion with less laser power, they needed to create an extremely low-mass mirror oscillator. They scaled down the 40-kilogram mirrors of Advanced LIGO with a 100-nanogram mirror oscillator (less than the mass of a grain of salt).

    The team also faced the significant challenge of designing a mirror oscillator that could exhibit quantum behavior at room temperature. Previously, observing quantum effects like QRPN required cryogenic cooling so that the motion due to heat energy of the oscillator would not mask the QRPN. In addition to being challenging and impractical, vibrations associated with cryogenic cooling interferes with LIGO’s operation, so conducting experiments at room temperature would be more readily applicable to LIGO itself. After many iterations of design and testing, Mavalvala and her MIT colleagues designed a mirror oscillator that allowed the team to reach a low enough level of thermally driven fluctuations that the mirror motion was dominated by QRPN at room temperature — the first-ever study to do so.

    “It’s really pretty mind-boggling that we can observe this room-temperature, macroscopic object — you can see it with the naked eye if you squint enough — being pushed around by quantum fluctuations,” Mavalvala says. “Its thermal jitter is small enough that it’s being tickled ever-so-slightly by quantum fluctuations, and we can measure that.”

    This was also the first study to detect QRPN at frequencies relevant to gravitational wave detectors. Their success means that they can now design additional experiments that reflect the radiation pressure conditions in Advanced LIGO itself.

    “This experiment mimics an important noise source in Advanced LIGO,” says Mavalvala. “It’s now a test bed where we can try out new ideas for improving Advanced LIGO without impinging on the instrument’s own operating time.”

    Advanced LIGO does not yet run its lasers at strong enough power for QRPN to be a limiting factor in gravitational wave detections. But, as the instruments become more sensitive, this type of noise will soon become a problem and limit Advanced LIGO’s capabilities. When Mavalvala and her collaborators recognized QRPN as an imminent issue, they strove to recreate its effects in the laboratory so that they can start exploring ways to overcome this challenge.

    “We’ve known for a long time that this QRPN would be a limitation for Advanced LIGO,” says Mavalvala. “Now that we are able to reproduce that effect in a laboratory setting, we can start to test ideas for how to improve that limit.”

    Mavalvala’s primary collaborator at LSU was Thomas Corbitt, an associate professor of physics and astronomy. Corbitt was formerly a graduate student and post-doctoral scholar in Mavalvala’s lab at MIT. They have since collaborated for many years.

    “This is the first time this effect has been observed in a system similar to gravitational wave interferometers and in LIGO’s frequency band,” says Corbitt. “While this work was motivated by the imperative to make ever-more-sensitive gravitational wave detectors, it is of wide interest.”

    New directions

    Since the original detection of a binary black hole merger in 2015, LIGO has also captured signals from collisions of neutron stars, as well as additional black hole collisions. These waves ripple outward from interactions that can take place more than a billion light years away. While LIGO’s capabilities are impressive, Mavalvala and her team plan to continue finding ways to make LIGO even more powerful.

    Before they collide, black holes, for example, orbit each other slowly and at lower frequencies. As the two black holes get closer, their orbits speed up and they swirl around each other at high speeds and high frequencies. If Advanced LIGO becomes sensitive enough to pick up lower frequencies, Mavalvala says we may someday detect these systems earlier in the process, before the pair collides, allowing us to draw an ever-clearer picture of these distant spacetime phenomena. She and her team aim to make sure that factors such as QRPN don’t limit Advanced LIGO’s growing power.

    “At this moment in time, Advanced LIGO is the best it can be at its job: to look out at the sky and detect gravitational wave events,” says Mavalvala. “In parallel, we have all of these ideas for making it better, and we have to be able to try those out in laboratories. This measurement allows that to happen with QRPN for the first time.”

    See the full article here .


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  • richardmitnick 11:26 am on April 26, 2019 Permalink | Reply
    Tags: , , , , , , Gravitational wave astronomy, IPTA-International Pulsar Timing Array, , , ,   

    From University of Maryland CMNS: “The Past, Present and Future of Gravitational Wave Astronomy” 

    U Maryland bloc

    From University of Maryland


    CMNS

    Matthew Wright
    301-405-9267
    mewright@umd.edu

    UMD Astronomy Professor Coleman Miller co-authored wide-ranging review article for 150th anniversary of the journal Nature.

    1
    Coleman Miller, University of Maryland Astronomy Professor and Co-Director of the Joint Space-Science Institute. Miller co-authored a new review of the past, present, and future of gravitational wave astronomy for the journal Nature. Image credit: Coleman Miller.

    When Albert Einstein published his general theory of relativity in 1915, he gave the scientific community a wealth of theoretical predictions about the nature of space, time, matter and gravity. Unlike much of his prior work, however, general relativity wasn’t easily testable with experiments and direct observation.

    That all changed a century later, on September 14, 2015, when the twin Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors registered gravitational waves from the merger of two black holes.

    For the first time, the scientific community had definitive support for one of the greatest predictions arising from Einstein’s general theory of relativity—that the acceleration of massive objects can produce ripples in the fabric of spacetime.

    In just three short years since that initial observation, LIGO has made or contributed to a landslide of new discoveries, helping to usher in the age of gravitational wave astronomy. University of Maryland Astronomy Professor Coleman Miller, an expert in the theory and modeling of gravity, co-authored a review of the past, present, and future of gravitational wave astronomy for the journal Nature, published on April 25, 2019. The article is part of a series that celebrates the 150th anniversary of the journal, which was first published on November 4, 1869.

    “Direct observation of gravitational waves was an important test of general relativity that gave us access to information we simply didn’t have before,” said Miller, who is also a co-director of the Joint Space-Science Institute (JSI), a partnership between UMD and NASA’s Goddard Space Flight Center. “There is a very limited set of ways we can get information about the distant universe beyond our solar system. We were missing a lot of non-trivial events before we could detect gravitational waves. To offer some perspective: the final plunge of a black hole merger emits tens of times more energy in gravitational waves than all the stars in the visible universe radiate within the same period of time.”

    Miller is a co-author of more than 20 publications related to gravitational radiation. Although he served as the chair of the LIGO Program Advisory Committee for four years (2010-2014), Miller has not been directly involved in LIGO’s science operations. This provides him with a uniquely knowledgeable, yet scientifically objective, viewpoint on the topic.

    Co-authored with Nicolás Yunes of Montana State University, the review article traces the early history of attempts to investigate general relativity, including several indirect observations and theoretical work. Then, Miller and Yunes describe the contributions of UMD Physics Professor Joseph Weber (1919-2000), who was the first to suggest that it was physically possible to detect and measure gravitational waves.

    Beginning in the 1960s, Weber designed, built and operated a pair of solid aluminum bars—one near UMD’s campus and another just outside Chicago—which he suggested would resonate like a bell when struck by passing gravitational waves. Thus began a decades-long scientific quest that would involve hundreds of scientists the world over, including many UMD faculty and staff members and alumni. The physics community eventually settled on a completely different interferometer design that would become the basis for LIGO’s twin detector facilities in Livingston, Louisiana, and Hanford, Washington.

    3
    The collision of two black holes—a tremendously powerful event detected for the first time ever by the Laser Interferometer Gravitational-Wave Observatory, or LIGO on September 14, 2015—is seen in this still from a computer simulation. LIGO detected gravitational waves, or ripples in space and time generated as the black holes spiraled in toward each other, collided, and merged. This simulation shows how the merger would appear to human eyes. It was created by solving equations from Albert Einstein’s general theory of relativity using the LIGO data. Illustration: SXS.

    With the help of UMD Physics Professor and JSI Fellow Peter Shawhan and UMD College Park Professor of Physics Alessandra Buonanno—both principal investigators with the LIGO Scientific Collaboration—the construction and fine-tuning of the detectors resulted in LIGO’s historic first observation in 2015. Just two years later, in 2017, LIGO project leads Rainer Weiss of the Massachusetts Institute of Technology and Kip Thorne and Barry Barish of Caltech were recognized with the Nobel Prize in physics for the groundbreaking observation.

    LIGO followed the initial 2015 detection with several more observations of black hole mergers. But another major turning point came on August 17, 2017, when scientists across the world made the first direct observation of a merger between two neutron stars—the dense, collapsed cores that remain after large stars die in a supernova. The merger was the first cosmological event observed in both gravitational waves and—with the help of a large array of ground- and space-based telescopes—the entire spectrum of light, from gamma rays to radio waves.

    “This event gave us instant confirmation that gravitational waves travel at a speed that is indistinguishable from the speed of light,” Miller explained. “For years, there have been alternate theories of gravity that would explain what dark matter is thought to do. But many of these relied on gravitational waves reacting to the gravity of massive objects differently than light does. This was not found to be the case in the wake of a neutron star merger, so observing this event eliminated a wide swath of these theories immediately.”

    The neutron star merger also yielded the first direct observation of a kilonova—a massive explosion now believed to create most of the heavy elements in the universe. Led by UMD’s Eleonora Troja, an associate research scientist in the Department of Astronomy, an early analysis of the kilonova suggested that the explosion produced a staggering amount of platinum and gold, with a combined mass several hundred times that of Earth.

    4
    This iconc illustration depicts the merger of two neutron stars. The rippling spacetime grid represents gravitational waves that travel out from the collision, while the narrow beams show the burst of gamma rays launched just seconds after the gravitational waves. Swirling clouds of material ejected from the merging stars glow with visible and other wavelengths of light. Image credit: National Science Foundation/LIGO/Sonoma State University/A. Simonnet

    This finding alone strongly swung the needle toward a conclusion that all elements heavier than iron are all produced in neutron star mergers,” Miller explained. “That’s very exciting.”

    On April 1, 2019, LIGO began its third observing run, after a series of upgrades to its lasers, mirrors and other components. While Miller is hesitant to set his own expectations too high, he is hopeful that the latest round will yield some new surprises.

    “The universe will give us what it will give us. That said, it would be wonderful to see a merger between a black hole and a neutron star,” Miller said. “And a few extra double neutron star mergers certainly wouldn’t hurt.”

    Looking further down the line, Miller and Yunes also assessed the prospects for observing the gravitational wave background. This ever-present hum of gravitational waves is thought to contain the fingerprints of orbiting black holes, neutron stars and other massive objects. These pairs of objects may be tens, hundreds or even thousands of years away from merging—and thus are unable to produce a spike in gravitational waves detectable with current technology. Miller likens the effort to adjusting one’s ears to the din of conversation in a crowded room.

    “Imagine arriving at a party. At first, you can see that everyone is talking, but the sound registers quietly, if at all,” Miller said. “Then your hearing gets better. You’re not yet able to hear every individual, but you can hear the sum total. Then, as your hearing gets better, you can hear some nearby conversations and can distinguish between people who are near and far.”

    Within the next few years, the International Pulsar Timing Array (IPTA) collaboration could become the first to detect the subtle drone from thousands of pairs of supermassive black holes.

    4

    With the help of the world’s largest radio telescopes, IPTA will carefully track deviations in the precise, clock-like flashing of roughly 100 small, rotating neutron stars called millisecond pulsars. These deviations will help IPTA detect gravitational fluctuations from orbiting pairs of supermassive black holes, each of which contains billions of times the mass of the sun.

    The next big step in gravitational wave astronomy will be the launch of the Laser Interferometer Space Antenna (LISA) mission, led by the European Space Agency in partnership with NASA.


    ESA/NASA eLISA space based, the future of gravitational wave research

    This trio of satellites, currently slated for deployment by 2034, will be sensitive to a lower range of gravitational wave frequencies than LIGO. As such, LISA should be able to observe events that LIGO cannot detect, such as mergers that involve one or more supermassive black holes.

    “A lot can happen in 15 years. In the meantime, I plan to eat my vegetables so I can be around to appreciate LISA’s findings when the satellites are launched,” Miller said. “The excitement in the astrophysical community is only increasing. Expectation of new discovery has been one the enduring excitements of gravitational wave astronomy.”

    See the full article here .

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    About CMNS

    The thirst for new knowledge is a fundamental and defining characteristic of humankind. It is also at the heart of scientific endeavor and discovery. As we seek to understand our world, across a host of complexly interconnected phenomena and over scales of time and distance that were virtually inaccessible to us a generation ago, our discoveries shape that world. At the forefront of many of these discoveries is the College of Computer, Mathematical, and Natural Sciences (CMNS).

    CMNS is home to 12 major research institutes and centers and to 10 academic departments: astronomy, atmospheric and oceanic science, biology, cell biology and molecular genetics, chemistry and biochemistry, computer science, entomology, geology, mathematics, and physics.

    Our Faculty

    Our faculty are at the cutting edge over the full range of these disciplines. Our physicists fill in major gaps in our fundamental understanding of matter, participating in the recent Higgs boson discovery, and demonstrating the first-ever teleportation of information between atoms. Our astronomers probe the origin of the universe with one of the world’s premier radio observatories, and have just discovered water on the moon. Our computer scientists are developing the principles for guaranteed security and privacy in information systems.

    Our Research

    Driven by the pursuit of excellence, the University of Maryland has enjoyed a remarkable rise in accomplishment and reputation over the past two decades. By any measure, Maryland is now one of the nation’s preeminent public research universities and on a path to become one of the world’s best. To fulfill this promise, we must capitalize on our momentum, fully exploit our competitive advantages, and pursue ambitious goals with great discipline and entrepreneurial spirit. This promise is within reach. This strategic plan is our working agenda.

    The plan is comprehensive, bold, and action oriented. It sets forth a vision of the University as an institution unmatched in its capacity to attract talent, address the most important issues of our time, and produce the leaders of tomorrow. The plan will guide the investment of our human and material resources as we strengthen our undergraduate and graduate programs and expand research, outreach and partnerships, become a truly international center, and enhance our surrounding community.

    Our success will benefit Maryland in the near and long term, strengthen the State’s competitive capacity in a challenging and changing environment and enrich the economic, social and cultural life of the region. We will be a catalyst for progress, the State’s most valuable asset, and an indispensable contributor to the nation’s well-being. Achieving the goals of Transforming Maryland requires broad-based and sustained support from our extended community. We ask our stakeholders to join with us to make the University an institution of world-class quality with world-wide reach and unparalleled impact as it serves the people and the state of Maryland.

    Our researchers are also at the cusp of the new biology for the 21st century, with bioscience emerging as a key area in almost all CMNS disciplines. Entomologists are learning how climate change affects the behavior of insects, and earth science faculty are coupling physical and biosphere data to predict that change. Geochemists are discovering how our planet evolved to support life, and biologists and entomologists are discovering how evolutionary processes have operated in living organisms. Our biologists have learned how human generated sound affects aquatic organisms, and cell biologists and computer scientists use advanced genomics to study disease and host-pathogen interactions. Our mathematicians are modeling the spread of AIDS, while our astronomers are searching for habitable exoplanets.

    Our Education

    CMNS is also a national resource for educating and training the next generation of leaders. Many of our major programs are ranked among the top 10 of public research universities in the nation. CMNS offers every student a high-quality, innovative and cross-disciplinary educational experience that is also affordable. Strongly committed to making science and mathematics studies available to all, CMNS actively encourages and supports the recruitment and retention of women and minorities.

    Our Students

    Our students have the unique opportunity to work closely with first-class faculty in state-of-the-art labs both on and off campus, conducting real-world, high-impact research on some of the most exciting problems of modern science. 87% of our undergraduates conduct research and/or hold internships while earning their bachelor’s degree. CMNS degrees command respect around the world, and open doors to a wide variety of rewarding career options. Many students continue on to graduate school; others find challenging positions in high-tech industry or federal laboratories, and some join professions such as medicine, teaching, and law.

     
  • richardmitnick 3:48 pm on April 16, 2019 Permalink | Reply
    Tags: A bright burst of X-rays has been discovered by NASA's Chandra X-ray Observatory in a galaxy 6.6 billion light years from Earth., , , , Chandra observed the source dubbed XT2 as it suddenly appeared and then faded away after about seven hours., , Gravitational wave astronomy, , , , The neutron star merger produced a new larger neutron star and not a black hole., This event likely signaled the merger of two neutron stars and could give astronomers fresh insight into how neutron stars — dense stellar objects packed mainly with neutrons — are built.   

    From NASA Chandra: “A New Signal for a Neutron Star Collision Discovered” 

    NASA Chandra Banner

    NASA/Chandra Telescope


    From NASA Chandra

    April 16, 2019

    Megan Watzke
    Chandra X-ray Center, Cambridge, Mass.
    617-496-7998
    mwatzke@cfa.harvard.edu

    1
    Credit: X-ray: NASA/CXC/Uni. of Science and Technology of China/Y. Xue et al; Optical: NASA/STScI

    A bright burst of X-rays has been discovered by NASA’s Chandra X-ray Observatory in a galaxy 6.6 billion light years from Earth. This event likely signaled the merger of two neutron stars and could give astronomers fresh insight into how neutron stars — dense stellar objects packed mainly with neutrons — are built.

    When two neutron stars merge they produce jets of high energy particles and radiation fired in opposite directions. If the jet is pointed along the line of sight to the Earth, a flash, or burst, of gamma rays can be detected. If the jet is not pointed in our direction, a different signal is needed to identify the merger.

    The detection of gravitational waves — ripples in spacetime — is one such signal. Now, with the observation of a bright flare of X-rays, astronomers have found another signal, and discovered that two neutron stars likely merged to form a new, heavier and fast-spinning neutron star with an extraordinarily strong magnetic field.

    “We’ve found a completely new way to spot a neutron star merger,” said Yongquan Xue of the University of Science and Technology of China and lead author of a paper appearing in Nature. “The behavior of this X-ray source matches what one of our team members predicted for these events.”

    Chandra observed the source, dubbed XT2, as it suddenly appeared and then faded away after about seven hours.The source is located in the Chandra Deep Field-South, the deepest X-ray image ever taken that contains almost 12 weeks of Chandra observing time, taken at various intervals over several years. The source appeared on March 22nd, 2015 and was discovered later in analysis of archival data.

    “The serendipitous discovery of XT2 makes another strong case that nature’s fecundity repeatedly transcends human imagination,”said co-author Niel Brandt of the Pennsylvania State University and principal investigator of the relevant Chandra Deep Field-South.

    The researchers identified the likely origin of XT2 by studying how its X-ray light varied with time, and comparing this behavior with predictions made in 2013 by Bing Zhang from the University of Nevada in Las Vegas, one of the corresponding authors of the paper. The X-rays showed a characteristic signature that matched those predicted for a newly-formed magnetar — a neutron star spinning around hundreds of times per second and possessing a tremendously strong magnetic field about a quadrillion times that of Earth’s.

    The team think that the magnetar lost energy in the form of an X-ray-emitting wind, slowing down its rate of spin as the source faded. The amount of X-ray emission stayed roughly constant in X-ray brightness for about 30 minutes, then decreased in brightness by more than a factor of 300 over 6.5 hours before becoming undetectable. This showed that the neutron star merger produced a new, larger neutron star and not a black hole.

    This result is important because it gives astronomers a chance to learn about the interior of neutron stars, objects that are so dense that their properties could never be replicated on Earth.

    “We can’t throw neutron stars together in a lab to see what happens, so we have to wait until the Universe does it for us,” said Zhang. “If two neutron stars can collide and a heavy neutron star survives, then this tells us that their structure is relatively stiff and resilient.”

    Neutron star mergers have been prominent in the news since the advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) detected gravitational waves from one in 2017. That source, known as GW170817, produced a burst of gamma rays and an afterglow in light detected by many other telescopes, including Chandra. Xue’s team think that XT2 would also have been a source of gravitational waves, however it occurred before Advanced LIGO started its first observing run, and it was too distant to have been detected in any case.

    Xue’s team also considered whether the collapse of a massive star could have caused XT2, rather than a neutron star merger. The source is in the outskirts of its host galaxy, which aligns with the idea that supernova explosions that left behind the neutron stars kicked them out of the center a few billion years earlier. The galaxy itself also has certain properties — including a low rate of star formation compared to other galaxies of a similar mass — that are much more consistent with the type of galaxy where the merger of two neutron stars is expected to occur.Massive stars are young and are associated with high rates of star formation.

    “The host-galaxy properties of XT2 indeed boost our confidence in explaining its origin,”said co-author Ye Li from Peking University.

    The team estimated the rate at which events like XT2 should occur, and found that it agrees with the rate deduced from the detection of GW170817. However, both estimates are highly uncertain because they depend on the detection of just one object each, so more examples are needed.

    “We’ve started looking at other Chandra data to see if similar sources are present”, said co-author Xuechen Cheng, also of the University of Science and Technology of China. “Just as with this source, the data sitting in archives might contain some unexpected treasures.”

    A paper describing these results appeared in the April 11th issue of Nature.

    Other materials about the findings are available at:
    http://chandra.si.edu

    For more Chandra images, multimedia and related materials, visit:
    http://www.nasa.gov/chandra

    See the full article here.


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    Please help promote STEM in your local schools.

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    NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

     
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