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  • richardmitnick 12:17 pm on July 14, 2020 Permalink | Reply
    Tags: "Gravitational wave researchers go beyond the quantum limit", , , , Caltech/MIT Advanced aLigo, , , ,   

    From University of Birmingham UK: “Gravitational wave researchers go beyond the quantum limit” 

    From University of Birmingham UK

    14 Jul 2020

    Scientists working at the LIGO facility in the United States, including a team from the University of Birmingham, have demonstrated how the ultra-fine tuning of the instruments enable it to push the boundaries of fundamental laws of physics.

    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

    The US-based Laser Interferometer Gravitational-wave Observatory detects gravitational waves produced by catastrophic events in the universe, such as mergers of neutron stars and black holes. These space-time ripples are enabling scientists to observe gravitational effects in extreme conditions and probe fundamental questions about the universe and its history.

    In the core of the LIGO detectors are km-scale laser interferometers that measure the distance between 40 kg suspended mirrors with the best precision ever achieved. Typical LIGO sources – the gravitational waves – modulate the distance between the mirrors by 1/1000 of a nucleus size but are still observed with high fidelity. The unprecedented level of the LIGO sensitivity is achieved by the state-of-the-art engineering required to suppress vibrational and thermal noises in the detectors.

    At these levels of sensitivity, quantum mechanics starts to play an important role. The revolutionary and counter-intuitive theories developed in the 20th century typically describe the microscopic world, such as atoms and molecules, but also puts stringent constraints on the continuous measurement of the giant LIGO mirrors.

    Scientists at the LIGO site have now succeeded in looking below the so-called standard quantum limit – the limit when only natural quantum states are utilised in the measurement. Their results are published in Nature.

    The experiment the LIGO team carried out used non-classical ‘squeezed light’ which reduces quantum fluctuations of the laser field. Denis Martynov, one of the Birmingham scientists who contributed to the research, says: “Just a few years ago, this type of quantum behaviour would have been too weak to be observed. But new measurement techniques are now enabling us to go beyond these limits. Not only that, but the approach taken by LIGO scientists in these experiments means that future improvements and upgrades to the instruments can be made with increased confidence that they will yield the improved sensitivity that we are looking for.”

    The ability to make these measurements, opens up the possibility of reducing the effects of quantum mechanics and improving overall the sensitivity of the instruments. The research marks an important step towards making further improvements in the sensitivity of gravitational wave technologies, enabling instruments in the future to reach even further through space and time to detect the echoes of these massive collisions.

    See the full article here .


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    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.

  • richardmitnick 12:17 pm on July 9, 2020 Permalink | Reply
    Tags: "ASKAP searches for afterglow of gravitational wave", , , , Caltech/MIT Advanced aLigo, , , LIGO-Virgo Finds Mystery Object in "Mass Gap"   

    From CSIROscope: “ASKAP searches for afterglow of gravitational wave” 

    CSIRO bloc

    From CSIROscope

    24 June 2020
    Annabelle Young

    Scientists have made a new gravitational waves discovery. Image credit: C. Knox/ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav).

    Scientists are puzzled by a new gravitational waves discovery. Have they discovered the heaviest neutron star or the lightest black hole ever observed?

    More than a century ago, Albert Einstein predicted massive objects like neutron stars and black holes produce ripples in space as they orbit one another and eventually merge in a violent clash.

    Gravitational waves from a black hole merger were first detected in 2015. Two years later researchers found not only gravitational waves but gamma-rays, light and radio waves from the merger of a pair of neutron stars.

    The Laser Interferometer Gravitational-Wave Observatory (LIGO) discovered these gravitational waves or ‘ripples’ in space.

    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

    It bagged three of its founders the 2017 Nobel prize in physics.

    LIGO’s system of lasers, mirrors and vacuum tubes make it the most precise ‘ruler’ on Earth. It’s capable of detecting these previously invisible ripples in space, which are smaller than the diameter of a proton.

    In August 2019, astronomers received an alert that LIGO had detected gravitational waves from a new type of event. The long-awaited merger of a suspected neutron star and a black hole!

    ASKAP [below] on patrol for a gravitational waves discovery

    Within minutes of receiving the alert, a team led by Professor Tara Murphy at The University of Sydney activated plans to use our ASKAP radio telescope. They were searching for the afterglow produced by the merger.

    Because gravitational waves are so hard to detect, LIGO can’t pinpoint where these mergers occur. So, they send the astronomy community a ‘sky map’ indicating a region where the event happened. Often these maps cover as much as a quarter of the sky. This takes hundreds of hours to search using a regular telescope.

    ASKAP is equipped with novel receivers that give it a wide-angle lens on the sky. In one pointing, ASKAP can view an area of sky about the size of the Southern Cross.

    Coincidentally, the sky map sent by LIGO for the detection of this merger was about the same size as ASKAP’s field of view. This allowed Tara’s team to observe almost the whole area of the map at once.

    Nine days after the merger, the ASKAP team found a source known as AT2019osy that had nearly doubled in brightness over the course of a week. The smoking gun of a radio afterglow?

    “We immediately alerted thousands of astronomers involved in the gravitational wave follow-up effort, and telescopes across the world, and in space, began slewing to observe our candidate,” team member Dougal Dobie, a co-supervised PhD student at The University of Sydney and CSIRO said.

    False start but the tide’s rising

    “Unfortunately, these observations suggested AT2019osy was produced by normal activity from the black hole at the centre of a galaxy and unrelated to the merger,” Dougal said.

    Continued ASKAP searches didn’t find any other candidates. This might seem disappointing but the ASKAP team say the effort was not wasted. A non-detection rules out several scenarios and helps place limits on the energy released during the merger.

    Hints of a deeper mystery

    Ongoing analysis of the LIGO data has shown the lack of a radio counterpart may even support the idea something unexpected is happening. The signal received by LIGO when a merger occurs depends on the mass of the two objects involved. Initial analysis suggested the merger of a neutron star and a black hole. But a recent announcement suggests this may not be the entire story.


    “We may have discovered either the heaviest neutron star or the lightest black hole ever observed. If it really is a heavy neutron star, this will radically alter our understanding of nuclear matter in the densest, most extreme environments in the Universe,” Rory Smith from OzGrav-Monash University said.

    The presence or absence of a radio counterpart may help tip the balance one way or another.

    Catching the next wave

    The era of gravitational wave research is still young. As the sensitivity of LIGO improves, it will detect more mergers at even greater distances.

    “This is just the tip of the iceberg. ASKAP’s fast survey capability will enable us to probe the sky deeper and wider than ever before, playing a key role in understanding these mergers,” Tara said.

    We acknowledge the Wajarri Yamatji as the traditional owners of the Murchison Radio-astronomy Observatory site.

    See the full article here .


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    Australian Square Kilometre Array Pathfinder (ASKAP) is a radio telescope array located at Murchison Radio-astronomy Observatory (MRO) in the Australian Mid West. ASKAP consists of 36 identical parabolic antennas, each 12 metres in diameter, working together as a single instrument with a total collecting area of approximately 4,000 square metres.

    So what can we expect these new radio projects to discover? We have no idea, but history tells us that they are almost certain to deliver some major surprises.

    Making these new discoveries may not be so simple. Gone are the days when astronomers could just notice something odd as they browse their tables and graphs.

    Nowadays, astronomers are more likely to be distilling their answers from carefully-posed queries to databases containing petabytes of data. Human brains are just not up to the job of making unexpected discoveries in these circumstances, and instead we will need to develop “learning machines” to help us discover the unexpected.

    With the right tools and careful insight, who knows what we might find.

    CSIRO campus

    CSIRO, the Commonwealth Scientific and Industrial Research Organisation, is Australia’s national science agency and one of the largest and most diverse research agencies in the world.

  • richardmitnick 11:33 am on July 7, 2020 Permalink | Reply
    Tags: "Quantum fluctuations can jiggle objects on the human scale", , Caltech/MIT Advanced aLigo, , ,   

    From MIT News and Caltech: “Quantum fluctuations can jiggle objects on the human scale” 

    Caltech Logo

    From Caltech


    MIT News

    MIT News

    July 1, 2020
    Jennifer Chu

    MIT physicists have observed that LIGO’s 40-kilogram mirrors can move in response to tiny quantum effects. In this photo, a LIGO optics technician inspects one of LIGO’s mirrors. Credit: Matt Heintze/Caltech/MIT/LIGO Lab

    Study shows LIGO’s 40-kilogram mirrors can move in response to tiny quantum effects, revealing the “spooky popcorn of the universe.”

    The universe, as seen through the lens of quantum mechanics, is a noisy, crackling space where particles blink constantly in and out of existence, creating a background of quantum noise whose effects are normally far too subtle to detect in everyday objects.

    Now for the first time, a team led by researchers at MIT LIGO Laboratory has measured the effects of quantum fluctuations on objects at the human scale. In a paper published today in Nature, the researchers report observing that quantum fluctuations, tiny as they may be, can nonetheless “kick” an object as large as the 40-kilogram mirrors of the U.S. National Science Foundation’s Laser Interferometer Gravitational-wave Observatory (LIGO), causing them to move by a tiny degree, which the team was able to measure.

    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

    It turns out the quantum noise in LIGO’s detectors is enough to move the large mirrors by 10^20 meters — a displacement that was predicted by quantum mechanics for an object of this size, but that had never before been measured.

    “A hydrogen atom is 10^10 meters, so this displacement of the mirrors is to a hydrogen atom what a hydrogen atom is to us — and we measured that,” says Lee McCuller, a research scientist at MIT’s Kavli Institute for Astrophysics and Space Research.

    The researchers used a special instrument that they designed, called a quantum squeezer, to “manipulate the detector’s quantum noise and reduce its kicks to the mirrors, in a way that could ultimately improve LIGO’s sensitivity in detecting gravitational waves,” explains Haocun Yu, a physics graduate student at MIT.

    “What’s special about this experiment is we’ve seen quantum effects on something as large as a human,” says Nergis Mavalvala, the Marble Professor and associate head of the physics department at MIT. “We too, every nanosecond of our existence, are being kicked around, buffeted by these quantum fluctuations. It’s just that the jitter of our existence, our thermal energy, is too large for these quantum vacuum fluctuations to affect our motion measurably. With LIGO’s mirrors, we’ve done all this work to isolate them from thermally driven motion and other forces, so that they are now still enough to be kicked around by quantum fluctuations and this spooky popcorn of the universe.”

    Yu, Mavalvala, and McCuller are co-authors of the new paper, along with graduate student Maggie Tse and Principal Research Scientist Lisa Barsotti at MIT, along with other members of the LIGO Scientific Collaboration.

    A quantum kick

    LIGO is designed to detect gravitational waves arriving at the Earth from cataclysmic sources millions to billions of light years away. It comprises twin detectors, one in Hanford, Washington, and the other in Livingston, Louisiana. Each detector is an L-shaped interferometer made up of two 4-kilometer-long tunnels, at the end of which hangs a 40-kilogram mirror.

    To detect a gravitational wave, a laser located at the input of the LIGO interferometer sends a beam of light down each tunnel of the detector, where it reflects off the mirror at the far end, to arrive back at its starting point. In the absence of a gravitational wave, the lasers should return at the same exact time. If a gravitational wave passes through, it would briefly disturb the position of the mirrors, and therefore the arrival times of the lasers.

    Much has been done to shield the interferometers from external noise, so that the detectors have a better chance of picking out the exceedingly subtle disturbances created by an incoming gravitational wave.

    Mavalvala and her colleagues wondered whether LIGO might also be sensitive enough that the instrument might even feel subtler effects, such as quantum fluctuations within the interferometer itself, and specifically, quantum noise generated among the photons in LIGO’s laser.

    “This quantum fluctuation in the laser light can cause a radiation pressure that can actually kick an object,” McCuller adds. “The object in our case is a 40-kilogram mirror, which is a billion times heavier than the nanoscale objects that other groups have measured this quantum effect in.”

    Noise squeezer

    To see whether they could measure the motion of LIGO’s massive mirrors in response to tiny quantum fluctuations, the team used an instrument they recently built as an add-on to the interferometers, which they call a quantum squeezer. With the squeezer, scientists can tune the properties of the quantum noise within LIGO’s interferometer.

    The team first measured the total noise within LIGO’s interferometers, including the background quantum noise, as well as “classical” noise, or disturbances generated from normal, everyday vibrations. They then turned the squeezer on and set it to a specific state that altered the properties of quantum noise specifically. They were able to then subtract the classical noise during data analysis, to isolate the purely quantum noise in the interferometer. As the detector constantly monitors the displacement of the mirrors to any incoming noise, the researchers were able to observe that the quantum noise alone was enough to displace the mirrors, by 10^20 meter.

    Mavalvala notes that the measurement lines up exactly with what quantum mechanics predicts. “But still it’s remarkable to see it be confirmed in something so big,” she says.

    Going a step further, the team wondered whether they could manipulate the quantum squeezer to reduce the quantum noise within the interferometer. The squeezer is designed such that when it set to a particular state, it “squeezes” certain properties of the quantum noise, in this case, phase and amplitude. Phase fluctuations can be thought of as arising from the quantum uncertainty in the light’s travel time, while amplitude fluctuations impart quantum kicks to the mirror surface.

    “We think of the quantum noise as distributed along different axes, and we try to reduce the noise in some specific aspect,” Yu says.

    When the squeezer is set to a certain state, it can for example squeeze, or narrow the uncertainty in phase, while simultaneously distending, or increasing the uncertainty in amplitude. Squeezing the quantum noise at different angles would produce different ratios of phase and amplitude noise within LIGO’s detectors.

    The group wondered whether changing the angle of this squeezing would create quantum correlations between LIGO’s lasers and its mirrors, in a way that they could also measure. Testing their idea, the team set the squeezer to 12 different angles and found that, indeed, they could measure correlations between the various distributions of quantum noise in the laser and the motion of the mirrors.

    Through these quantum correlations, the team was able to squeeze the quantum noise, and the resulting mirror displacement, down to 70 percent its normal level. This measurement, incidentally, is below what’s called the standard quantum limit, which, in quantum mechanics, states that a given number of photons, or, in LIGO’s case, a certain level of laser power, is expected to generate a certain minimum of quantum fluctuations that would generate a specific “kick” to any object in their path.

    By using squeezed light to reduce the quantum noise in the LIGO measurement, the team has made a measurement more precise than the standard quantum limit, reducing that noise in a way that will ultimately help LIGO to detect fainter, more distant sources of gravitational waves.

    This research was funded, in part, by the National Science Foundation.

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

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  • richardmitnick 9:40 am on July 6, 2020 Permalink | Reply
    Tags: "The supersizing of quantum physics", , Caltech/MIT Advanced aLigo, , , , Squeezer table   

    From Australian National University via COSMOS: “The supersizing of quantum physics” 

    ANU Australian National University Bloc

    From Australian National University


    Cosmos Magazine bloc


    3 July 2020
    Phil Dooley

    Quantum physics is the realm of tiny particles no longer. Scientists at the giant gravitational wave detector LIGO in the US are now measuring the quantum effects of 40-kilogram mirrors used to detect gravitational waves.

    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

    While physicists routinely observe quantum effects in nanometre-scale experiments, LIGO team member Robert Ward says this new level of sensitivity was unmatched in other experiments.

    ANU’s Nutsinee Kijbunchoo (left) and Terry McRae building a squeezer table at LIGO Hanford. Credit: ANU.

    “There’s nowhere else close, nothing like it. That’s as big as my kids!” says Ward, who is part of the OzGrav Research Centre based at the Australian National University (ANU).

    “The reality that we can measure to this level of precision on an instrument that is so large is incredible,” adds his ANU colleague Terry McRae, who recently spent a year installing new componentry at the Livingston site in Louisiana, US.

    Livingston is one of two linked gravitational wave detectors run by the LIGO organisation. Each detector is made of two high-powered laser beams at right angles, bouncing between mirrors four kilometres apart. The second is in Washington State, 3000 kilometres to the northwest.

    The LIGO team has published results in the journal Nature that accurately show quantum correlations between the 40-kilogram mirrors and the laser beam, which at 200 kilowatts is about 2000 times more powerful than a laser cutter.

    For the purpose of detecting gravitational waves, it has used the correlations and manipulated the quantum properties of the system, to reduce noise and make it more sensitive, a technique called quantum squeezing.

    The sensitivity of LIGO is crucial. Although black hole collisions are the most violent events known to humans, the gravitational waves from them reach earth as tiny flickers in space and time. In the triumphant first detections of gravitational waves, LIGO’s mirrors moved about a billionth of the diameter of the atoms making up the mirrors.

    The two-decade story of LIGO is one of tirelessly removing one noise source after another, says ANU’s Nutsinee Kijbunchoo.

    “We’re always trying to do better: sensitivity less than the width of a hair? Not good enough, we have to keep improving,” she says.

    Kijbunchoo worked with McRae on the recent upgrade at Livingston and was amazed to see people banging on parts of the apparatus to try to induce noise, characterise it precisely and work out how to cut it out.

    A recent paper [Physics]announced the new sensitivity levels reached, thanks to the new quantum squeezing system that Kijbunchoo and McRae were involved in installing. The paper estimated that the improvement would lead to a 50% jump in the rate of gravitational wave detections.

    This new paper takes a step back, however, and discusses the significance of the LIGO’s sensitivity, saying in its conclusions that “the measurements presented here represent long-awaited milestones in verifying the role of quantum mechanics in limiting the measurement of small displacements…”.

    Rob Ward says this moment has been a long time coming, citing Russian scientist Braginsky as one of the first to begin thinking [Reviews of Modern Physics] about the quantum limits of measurement in 1996.

    “Now we’ve crossed that threshold, and now we have to start thinking about the quantum mechanics of our test masses (mirrors). We’re being forced to grapple with the quantum mechanics of a human-sized objects,” Ward says.

    The quantum noise has been revealed after an intricate system of suspension wires, feedback systems, laser stabiliser and cooling systems have stabilised the experiment – removing the so-called classical noise.

    Credit: Nutsinee Kijbunchoo ANU.

    You would think all of these vibrations and wobbles could be cut out completely, but quantum noise is a fundamental property of a system, first expressed by Heisenberg in the famous Uncertainty Principle, which lays out that measurements have limits to their precision, beyond which you cannot pass, no matter how cold, stable or isolated your experiment is.

    But there is a loophole: these measurements come in pairs, and the uncertainty is distributed between the pairs, and can be shifted from one quantity to the other.

    Imagine cleaning the house, which you could measure by how fast it was done, or how clean the house ends up. The quicker the clean-up, the lower the final standard of cleanliness. Or, an exhaustive spring clean could take well past tea time.

    It’s this kind of trade-off that the squeezing system uses – in this case playing off the radiation pressure against the randomness in the arrival time of the photons. The trick is the photons need to be paired – correlated – which enables the quantum link to be leveraged.

    These play into the overall noise differently for different signals, so the LIGO scientists constrain the value of one that will make the experiment most sensitive, say to a neutron star merger, and let the other be a little less certain.

    This is how the LIGO detector achieves sensitivity that is better than non-quantum physics could have imagined – a limit known as the standard quantum limit (SQL).

    These quantum tricks can only be used if the overall noise is infinitesimal, otherwise the pairings become smeared out, and quantum effects can’t be seen.

    This is the case in our everyday world. But now, says Ward, with this exquisite instrument we’re in a realm we’ve never seen before.

    “We never normally see quantum effects of big objects, and we don’t exactly know why, but now we’re getting to that level of precision,” he says. “We’re exploring fundamental questions about reality.”

    See the full article here .


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    ANU is a world-leading university in Australia’s capital city, Canberra. Our location points to our unique history, ties to the Australian Government and special standing as a resource for the Australian people.

    Our focus on research as an asset, and an approach to education, ensures our graduates are in demand the world-over for their abilities to understand, and apply vision and creativity to addressing complex contemporary challenges.

  • richardmitnick 5:12 pm on June 25, 2020 Permalink | Reply
    Tags: "Black Hole Collision May Have Exploded with Light", , , , , , Caltech/MIT Advanced aLigo, ,   

    From Caltech: “Black Hole Collision May Have Exploded with Light” 

    Caltech Logo

    From Caltech

    June 25, 2020
    Whitney Clavin
    (626) 395‑1944

    Artist’s concept of a supermassive black hole and its surrounding disk of gas. Embedded within this disk are two smaller black holes orbiting one another. Using data from the Zwicky Transient Facility (ZTF) at Palomar Observatory, researchers have identified a flare of light suspected to have come from one such binary pair soon after they merged into a larger black hole. The merger of the black holes would have caused them to move in one direction within the disk, plowing through the gas in such a way to create a light flare. The finding, while not confirmed, could amount to the first time that light has been seen from a coalescing pair of black holes. These merging black holes were first spotted on May 21, 2019, by the National Science Foundation’s Laser Interferometer Gravitational-wave Observatory (LIGO) and the European Virgo detector, which picked up gravitational waves generated by the merger.
    Credit: Caltech/R. Hurt (IPAC)

    Zwicky Transient Facility (ZTF) instrument installed on the 1.2m diameter Samuel Oschin Telescope at Palomar Observatory in California. Courtesy Caltech Optical Observatories

    Caltech Palomar Samuel Oschin 48 inch Telescope, located in San Diego County, California, United States, altitude 1,712 m (5,617 ft)

    Possible light flare observed from small black holes within the disk of a massive black hole.

    When two black holes spiral around each other and ultimately collide, they send out ripples in space and time called gravitational waves. Because black holes do not give off light, these events are not expected to shine with any light waves, or electromagnetic radiation. But some theorists have come up with ways in which a black hole merger might explode with light. Now, for the first time, astronomers have seen evidence for one of these light-producing scenarios.

    With the help of Caltech’s Zwicky Transient Facility (ZTF), funded by the National Science Foundation (NSF) and located at Palomar Observatory near San Diego, the scientists have spotted what might be a flare of light from a pair of coalescing black holes. The black hole merger was first witnessed by the NSF’s Laser Interferometer Gravitational-wave Observatory (LIGO) and the European Virgo detector on May 21, 2019, in an event called S190521g. As the black holes merged, jiggling space and time, they sent out gravitational waves.

    MIT /Caltech Advanced aLigo

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    While this was happening, ZTF was performing its robotic survey of the sky that captured all kinds of objects that flare, erupt, or otherwise vary in the night sky. One flare the survey caught, generated by a distant active supermassive black hole, or quasar, called J1249+3449, was pinpointed to the region of the gravitational-wave event S190521g.

    “This supermassive black hole was burbling along for years before this more abrupt flare,” says Matthew Graham, a research professor of astronomy at Caltech and the project scientist for ZTF. “The flare occurred on the right timescale, and in the right location, to be coincident with the gravitational-wave event. In our study, we conclude that the flare is likely the result of a black hole merger, but we cannot completely rule out other possibilities.” Graham is lead author of the new study, published today, June 25, in the journal Physical Review Letters.

    “ZTF was specifically designed to identify new, rare, and variable types of astronomical activity like this,” says NSF Division of Astronomical Science Director Ralph Gaume. “NSF support of new technology continues to expand how we can track such events.”

    How do two merging black holes erupt with light? In the scenario outlined by Graham and his colleagues, two partner black holes were nestled within a disk surrounding a much larger black hole.

    “At the center of most galaxies lurks a supermassive black hole. It’s surrounded by a swarm of stars and dead stars, including black holes,” says co-author K. E. Saavik Ford of the City University of New York (CUNY) Graduate Center, the Borough of Manhattan Community College (BMCC), and the American Museum of Natural History (AMNH). “These objects swarm like angry bees around the monstrous queen bee at the center. They can briefly find gravitational partners and pair up but usually lose their partners quickly to the mad dance. But in a supermassive black hole’s disk, the flowing gas converts the mosh pit of the swarm to a classical minuet, organizing the black holes so they can pair up,” she says.

    Once the black holes merge, the new, now-larger black hole experiences a kick that sends it off in a random direction, and it plows through the gas in the disk. “It is the reaction of the gas to this speeding bullet that creates a bright flare, visible with telescopes,” says co-author Barry McKernan, also of the CUNY Graduate Center, BMCC, and AMNH.

    Such a flare is predicted to begin days to weeks after the initial splash of gravitational waves produced during the merger. In this case, ZTF did not catch the event right away, but when the scientists went back and looked through archival ZTF images months later, they found a signal that started days after the May 2019 gravitational-wave event. ZTF observed the flare slowly fade over the period of a month.

    The scientists attempted to get a more detailed look at the light of the supermassive black hole, called a spectrum, but by the time they looked, the flare had already faded. A spectrum would have offered more support for the idea that the flare came from merging black holes within the disk of the supermassive black hole. However, the researchers say they were able to largely rule out other possible causes for the observed flare, including a supernova or a tidal disruption event, which occurs when a black hole essentially eats a star.

    What is more, the team says it is not likely that the flare came from the usual rumblings of the supermassive black hole, which regularly feeds off its surrounding disk. Using the Catalina Real-Time Transient Survey, led by Caltech, they were able to assess the behavior of the black hole over the past 15 years, and found that its activity was relatively normal until May of 2019, when it suddenly intensified.

    “Supermassive black holes like this one have flares all the time. They are not quiet objects, but the timing, size, and location of this flare was spectacular,” says co-author Mansi Kasliwal (MS ’07, PhD ’11), an assistant professor of astronomy at Caltech. “The reason looking for flares like this is so important is that it helps enormously with astrophysics and cosmology questions. If we can do this again and detect light from the mergers of other black holes, then we can nail down the homes of these black holes and learn more about their origins.”

    The newly formed black hole should cause another flare in the next few years. The process of merging gave the object a kick that should cause it to enter the supermassive black hole’s disk again, producing another flash of light that ZTF should be able to see.

    The Physical Review Letters paper was funded by the NSF, NASA, the Heising-Simons Foundation, and the GROWTH (Global Relay of Observatories Watching Transients Happen) program. Other co-authors include: K. Burdge, S.G. Djorgovski, A.J. Drake, D. Duev, A.A. Mahabal, J. Belecki, R. Burruss, G. Helou, S.R. Kulkarni, F.J. Masci, T. Prince, D. Reiley, H. Rodriguez, B. Rusholme, R.M. Smith, all from Caltech; N.P. Ross of the University of Edinburgh; Daniel Stern of the Jet Propulsion Laboratory, managed by Caltech for NASA; M. Coughlin of the University of Minnesota; S. van Velzen of University of Maryland, College Park and New York University; E.C. Bellm of the University of Washington; S.B. Cenko of NASA Goddard Space Flight Center; V. Cunningham of University of Maryland, College Park; and M.T. Soumagnac of the Lawrence Berkeley National Laboratory and the Weizmann Institute of Science.

    In addition to the NSF, ZTF is funded by an international collaboration of partners, with additional support from NASA, the Heising-Simons Foundation, members of the Space Innovation Council at Caltech, and Caltech itself.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

    Caltech campus

  • richardmitnick 9:08 am on April 21, 2020 Permalink | Reply
    Tags: , , , , , Caltech/MIT Advanced aLigo, , , ,   

    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 .


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    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.

  • richardmitnick 11:38 am on March 30, 2020 Permalink | Reply
    Tags: "Big Labs Replace Data Taking with New Priorities", , Brookhaven National Laboratory’s National Synchrotron Light Source II (NSLS-II), Caltech/MIT Advanced aLigo, , ,   

    From “Physics”: “Big Labs Replace Data Taking with New Priorities” 

    About Physics

    From “Physics”

    March 30, 2020
    Katherine Wright

    Large research facilities have curtailed data collection and shut their doors—but their scientists are busier than ever, and some have joined the fight against COVID-19.

    Brookhaven National Laboratory

    Despite being stuck at home, John Hill has never been busier. As the director of Brookhaven National Laboratory’s National Synchrotron Light Source II (NSLS-II)—a state-of-the-art x-ray facility in New York—Hill spent the middle of March rapidly ramping down experiments in response to the COVID-19 pandemic. As of midday March 23rd, only two of the 28 beamlines at NSLS-II remained operational, and only a handful of staff were onsite.


    BNL NSLS-II Interior

    Like many large facilities, NSLS-II shut its doors to comply with government guidelines and to keep staff safe and healthy. These rapid closures have, in some cases, brought experiments to a grinding halt—LIGO in the US and Virgo in Italy both stopped their search for gravitational-wave signals on Friday, more than a month earlier than they’d planned before the pandemic. At other places, such as CERN in Switzerland, where detectors were already off, long-awaited upgrades are now on indefinite hold.

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation

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


    CERN map

    CERN LHC Maximilien Brice and Julien Marius Ordan

    CERN LHC particles

    The scientists in charge of major experiments are now scrambling to rethink the next few months. And even though most researchers from these facilities are housebound, they are still hard at work. Most have switched their attention to data analysis, paper writing, and software development, interspersed with virtual meetings. A small number of others remain onsite, busy with an unexpected focus: new experiments to understand the virus that causes COVID-19.

    “The last three weeks have been nonstop planning,” says David Reitze, the director of LIGO, who spoke from his home in California. “We had to react very quickly.” Reitze has been in daily meetings with his LIGO and Virgo colleagues to implement remote working procedures for its 1300 international team members, who are used to frequent in-person meetings. Until Friday, LIGO had kept a skeleton crew running its two detectors, but the collaboration decided to turn the detectors off. Reitze says it was sad to end early, but he wanted to keep the staff safe.

    In addition to making contingency plans, researchers are busy replacing their usual in-person meetings with virtual ones. LIGO and Virgo canceled their biannual conference, scheduled for March 16th at Lake Geneva in Wisconsin. “The risk of becoming a central spreader of the disease just didn’t seem like a good idea,” says Patrick Brady, the current spokesperson for the LIGO collaboration. Instead, attendees live-streamed talks, with around 200 people watching the plenary session. “It was a chance to focus on science,” Reitze says. “That brought a bit of normalcy.”

    The researchers interviewed for this story say that they expect little to no impact on the scientific output from their institutions—for now. Many places have loads of data to analyze already. The gravitational-wave community has 11 months of data and over 50 events to analyze from the latest observation run. Scientists using Diamond Light Source, a synchrotron in the UK, just finished a cycle of experiments.

    Diamond Light Source, located at the Harwell Science and Innovation Campus in Oxfordshire U.K.

    And CERN has been undergoing upgrades since December 2018, so many of the scientists were already focused on data analysis. “Eighteen months after a shutdown you often get a spike in publications as people write up all the work that they have perhaps fallen behind with,” says Andrew Harrison, the CEO of Diamond.

    That said, this shutdown is different from most. LIGO and Virgo expect to submit papers from this run later than initially planned, having added a four-week extension to their writing activities. “Because of the sense of anxiety that many people are feeling, we decided to relax our timelines,” Brady says.

    Physics output could be impacted if the shutdowns extend beyond a few months. At CERN, for example, the ongoing instrument and equipment upgrades have been deemed nonessential activities and are now on hiatus. “We had to drop the screwdrivers,” says Giovanni Passaleva, the spokesperson for CERN’s Large Hadron Collider Beauty (LHCb) experiment.

    CERN LHCb chamber, LHC

    Stopping the upgrade could potentially delay LHC’s plan to restart in May 2021. But with no equipment to attend to, Passaleva notes that updates to LHCb’s software are “going faster than before.” And his group is still committed to its daily coffee hour, only now they do it online. “It’s very important that we keep connections with each other,” he says.

    In-person interactions are still possible at some labs. At NSLS-II, a handful of scientists are onsite helping researchers from pharmaceutical companies and academia study the crystal structures of synthetic versions of proteins found in the virus that causes COVID-19. Their goal is to use this information to develop drugs for treating those infected with the disease, Hill says. Similar experiments are ongoing at the Advanced Photon Source at Argonne National Laboratory, Illinois, and will start tomorrow at two beamlines at Diamond, which as of Friday had received a dozen applications for experiments to study the proteins in the virus.

    ANL Advanced Photon Source

    Hill says it’s good for NSLS-II that it can continue to contribute. “We don’t feel we are sitting powerless, watching this disease come—we are actively trying to fight it.” Harrison echoes this sentiment, saying he is pleased that basic science is considered essential work and that Diamond can contribute in the effort to understand the new disease. “It’s very positive that governments are engaging [with scientists],” he says. He also thinks the situation has forced scientists to refocus their priorities. “The things you thought were important just completely change,” he says.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Physicists are drowning in a flood of research papers in their own fields and coping with an even larger deluge in other areas of physics. How can an active researcher stay informed about the most important developments in physics? Physics highlights a selection of papers from the Physical Review journals. In consultation with expert scientists, the editors choose these papers for their importance and/or intrinsic interest. To highlight these papers, Physics features three kinds of articles: Viewpoints are commentaries written by active researchers, who are asked to explain the results to physicists in other subfields. Focus stories are written by professional science writers in a journalistic style and are intended to be accessible to students and non-experts. Synopses are brief editor-written summaries. Physics provides a much-needed guide to the best in physics, and we welcome your comments (physics@aps.org).

  • richardmitnick 10:17 am on December 29, 2019 Permalink | Reply
    Tags: , Caltech/MIT Advanced aLigo, , , , , , ,   

    From particlebites: “Dark Photons in Light Places” 

    particlebites bloc

    From particlebites

    December 29, 2019
    Amara McCune

    Title: “Searching for dark photon dark matter in LIGO O1 data”

    Author: Huai-Ke Guo, Keith Riles, Feng-Wei Yang, & Yue Zhao

    Reference: https://www.nature.com/articles/s42005-019-0255-0

    There is very little we know about dark matter save for its existence.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)

    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)

    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    The LSST, or Large Synoptic Survey Telescope is to be named the Vera C. Rubin Observatory by an act of the U.S. Congress.

    LSST telescope, The Vera Rubin Survey Telescope currently under construction on the El Peñón peak 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.

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background [CMB] hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    CMB per ESA/Planck

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LBNL LZ Dark Matter project at SURF, Lead, SD, USA

    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    Its mass(es), its interactions, even the proposition that it consists of particles at all is mostly up to the creativity of the theorist. For those who don’t turn to modified theories of gravity to explain the gravitational effects on galaxy rotation and clustering that suggest a massive concentration of unseen matter in the universe (among other compelling evidence), there are a few more widely accepted explanations for what dark matter might be. These include weakly-interacting massive particles (WIMPS), primordial black holes, or new particles altogether, such as axions or dark photons.

    In particle physics, this latter category is what’s known as the “hidden sector,” a hypothetical collection of quantum fields and their corresponding particles that are utilized in theorists’ toolboxes to help explain phenomena such as dark matter. In order to test the validity of the hidden sector, several experimental techniques have been concocted to narrow down the vast parameter space of possibilities, which generally consist of three strategies:

    1.Direct detection: Detector experiments look for low-energy recoils of dark matter particle collisions with nuclei, often involving emitted light or phonons.
    2.Indirect detection: These searches focus on potential decay products of dark matter particles, which depends on the theory in question.
    3.Collider production: As the name implies, colliders seek to produce dark matter in order to study its properties. This is reliant on the other two methods for verification.

    The first detection of gravitational waves from a black hole merger in 2015 ushered in a new era of physics, in which the cosmological range of theory-testing is no longer limited to the electromagnetic spectrum.

    MIT /Caltech Advanced aLigo

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

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

    Caltech/MIT Advanced aLigo detector installation Hanford, WA, USA

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Gravity is talking. Lisa will listen. Dialogos of Eide

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

    Bringing LIGO (the Laser Interferometer Gravitational-Wave Observatory) to the table, proposals for the indirect detection of dark matter via gravitational waves began to spring up in the literature, with implications for primordial black hole detection or dark matter ensconced in neutron stars. Yet a new proposal, in a paper by Guo et. al., [Scientific Reports-Communication Physics] suggests that direct dark matter detection with gravitational waves may be possible, specifically in the case of dark photons.

    Dark photons are hidden sector particles in the ultralight regime of dark matter candidates. Theorized as the gauge boson of a U(1) gauge group, meaning the particle is a force-carrier akin to the photon of quantum electrodynamics, dark photons either do not couple or very weakly couple to Standard Model particles in various formulations. Unlike a regular photon, dark photons can acquire a mass via the Higgs mechanism. Since dark photons need to be non-relativistic in order to meet cosmological dark matter constraints, we can model them as a coherently oscillating background field: a plane wave with amplitude determined by dark matter energy density and oscillation frequency determined by mass. In the case that dark photons weakly interact with ordinary matter, this means an oscillating force is imparted. This sets LIGO up as a means of direct detection due to the mirror displacement dark photons could induce in LIGO detectors.

    Figure 1: The experimental setup of the Advanced LIGO interferometer. We can see that light leaves the laser and is reflected between a few power recycling mirrors (PR), split by a beam splitter (BS), and bounced between input and end test masses (ITM and ETM). The entire system is mounted on seismically-isolated platforms to reduce noise as much as possible. Source: https://arxiv.org/pdf/1411.4547.pdf

    LIGO consists of a Michelson interferometer, in which a laser shines upon a beam splitter which in turn creates two perpendicular beams. The light from each beam then hits a mirror, is reflected back, and the two beams combine, producing an interference pattern. In the actual LIGO detectors, the beams are reflected back some 280 times (down a 4 km arm length) and are split to be initially out of phase so that the photodiode detector should not detect any light in the absence of a gravitational wave. A key feature of gravitational waves is their polarization, which stretches spacetime in one direction and compresses it in the perpendicular direction in an alternating fashion. This means that when a gravitational wave passes through the detector, the effective length of one of the interferometer arms is reduced while the other is increased, and the photodiode will detect an interference pattern as a result.

    LIGO has been able to reach an incredible sensitivity of one part in 10^{23} in its detectors over a 100 Hz bandwidth, meaning that its instruments can detect mirror displacements up to 1/10,000th the size of a proton. Taking advantage of this number, Guo et. al. demonstrated that the differential strain (the ratio of the relative displacement of the mirrors to the interferometer’s arm length, or h = \Delta L/L) is also sensitive to ultralight dark matter via the modeling process described above. The acceleration induced by the dark photon dark matter on the LIGO mirrors is ultimately proportional to the dark electric field and charge-to-mass ratio of the mirrors themselves.

    Once this signal is approximated, next comes the task of estimating the background. Since the coherence length is of order 10^9 m for a dark photon field oscillating at order 100 Hz, a distance much larger than the separation between the LIGO detectors at Hanford and Livingston (in Washington and Louisiana, respectively), the signals from dark photons at both detectors should be highly correlated. This has the effect of reducing the noise in the overall signal, since the noise in each of the detectors should be statistically independent. The signal-to-noise ratio can then be computed directly using discrete Fourier transforms from segments of data along the total observation time. However, this process of breaking up the data, known as “binning,” means that some signal power is lost and must be corrected for.

    Figure 2: The end result of the Guo et. al. analysis of dark photon-induced mirror displacement in LIGO. Above we can see a plot of the coupling of dark photons to baryons as a function of the dark photon oscillation frequency. We can see that over further Advanced LIGO runs, up to O4-O5, these limits are expected to improve by several orders of magnitude. Source: https://www.nature.com/articles/s42005-019-0255-0

    In applying this analysis to the strain data from the first run of Advanced LIGO, Guo et. al. generated a plot which sets new limits for the coupling of dark photons to baryons as a function of the dark photon oscillation frequency. There are a few key subtleties in this analysis, primarily that there are many potential dark photon models which rely on different gauge groups, yet this framework allows for similar analysis of other dark photon models. With plans for future iterations of gravitational wave detectors, further improved sensitivities, and many more data runs, there seems to be great potential to apply LIGO to direct dark matter detection. It’s exciting to see these instruments in action for discoveries that were not in mind when LIGO was first designed, and I’m looking forward to seeing what we can come up with next!

    Learn More:

    An overview of gravitational waves and dark matter: https://www.symmetrymagazine.org/article/what-gravitational-waves-can-say-about-dark-matter
    A summary of dark photon experiments and results: https://physics.aps.org/articles/v7/115
    Details on the hardware of Advanced LIGO: https://arxiv.org/pdf/1411.4547.pdf
    A similar analysis done by Pierce et. al.: https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.121.061102

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    What is ParticleBites?

    ParticleBites is an online particle physics journal club written by graduate students and postdocs. Each post presents an interesting paper in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.

    The papers are accessible on the arXiv preprint server. Most of our posts are based on papers from hep-ph (high energy phenomenology) and hep-ex (high energy experiment).

    Why read ParticleBites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.

    Our goal is to solve this problem, one paper at a time. With each brief ParticleBite, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in particle physics.

    Who writes ParticleBites?

    ParticleBites is written and edited by graduate students and postdocs working in high energy physics. Feel free to contact us if you’re interested in applying to write for ParticleBites.

    ParticleBites was founded in 2013 by Flip Tanedo following the Communicating Science (ComSciCon) 2013 workshop.

    Flip Tanedo UCI Chancellor’s ADVANCE postdoctoral scholar in theoretical physics. As of July 2016, I will be an assistant professor of physics at the University of California, Riverside

    It is now organized and directed by Flip and Julia Gonski, with ongoing guidance from Nathan Sanders.

  • richardmitnick 9:40 am on August 31, 2019 Permalink | Reply
    Tags: "Scientists Detected 2 Black Hole Mergers Just 21 Mins Apart But It's Not What We Hoped", , Caltech/MIT Advanced aLigo, , ,   

    From Science Alert and LIGO: “Scientists Detected 2 Black Hole Mergers Just 21 Mins Apart, But It’s Not What We Hoped” 


    From Science Alert

    MIT /Caltech Advanced aLigo

    31 AUG 2019

    (Des Green/iStock)

    Last Wednesday, a gravitational wave detection gave astronomers quite the surprise. As researchers were going about their work at the Laser Interferometer Gravitational-Wave Observatory (LIGO), a pair of gravitational waves rolled in just minutes apart.

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

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    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

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

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    The first, labelled S190828j, was picked up by all three of LIGO’s gravitational wave detectors at 06:34 am, coordinated universal time.

    MIT /Caltech Advanced aLigo

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    The second, S190828l, was measured at 06:55 – a mere 21 minutes later.

    Both seemed to be the run-of-the-mill dying screams of black holes as they squish together. But here’s why it’s so surprising: astronomers wouldn’t expect to see a pair of signals in such quick succession.

    In fact, this is only the second time two detections have rolled in on the same day. What’s more, at first glance they also seemed to echo from more or less the same patch of sky.

    “This is a genuine “Uh, wait, what?; We’ve never seen that before…” moment in gravitational wave astronomy,” astrophysicist Robert Routledge from McGill University later tweeted, after openly speculating that it mightn’t be a mere coincidence.

    Non-scientists — this is a genuine “Uh, wait, what? We’ve never seen that before…….” moment in gravitational wave astronomy. If you’d like to see how double-checks and confirmations and conclusions occur – pay attention, in real time. Happening now.
    — Robert Rutledge (@rerutled) August 28, 2019

    Nobody can blame Routledge for getting excited. Unexpected events like this are what discoveries are made of, after all. As he said, this is science in real time.

    One possibility briefly kicked around was that S190828j and S190828l were actually the same wave, divided by some sort of distortion in space before being roughly thrown together again. This would have been huge.

    Gravitational lensing – the warping effect an intervening mass has on space, as described by general relativity – can divide and duplicate the rays of light from far-off objects. It has become a useful tool for astronomers in the measurement of distances.

    Gravitational Lensing NASA/ESA

    If this had indeed been a two-for-one deal, it would be the first time a gravitational wave had been observed through a gravitational lens.

    Alas, it’s now looking pretty unlikely. As the hours passed, new details emerged indicating the two signals don’t overlap enough to be originating from the same source.

    If this were a lensing event, you’d expect the two localizations to sit more or less right on top of each other. They have similar shapes and appear in the same part of the sky, but they don’t really overlap: pic.twitter.com/lqvigNhyBl
    — Robert McNees (@mcnees) August 28, 2019

    So close, and yet so far. Right now, this twin event is looking more like a coincidence.

    To look on the bright side, we now live in an age where the detection of the crash-boom of galactic giants isn’t a rare event, but rather an endless peel of thunder we can record and measure with an insane level of accuracy. It’s hard to believe the first collision was detected only a few years ago.

    Scientists face a problem in the wake of freaky events like this one. On the one hand, wild speculations have a habit of taking on a life of their own when discussed so frankly in a public space, transforming into an established fact while barely half baked.

    But time can be of the essence when we’re scanning a near-infinite amount of sky for clues, too. By throwing ideas out broadly, different groups of researchers can turn their attention to a phenomenon and collect data while it’s still hot.

    This is what scientists do best – stumble across odd events, throw out ideas, and debate which ones deserve to be inspected and which should be abandoned.

    If there’s more to S190828j and S190828l than meets the eye, we’ll let you know. For now, we can be disappointed that there was no Earth-shaking discovery, while still being amazed that we have the technology to discover it at all.

    We really ought to celebrate the ‘disappointments’ a little more often.

    See the full article here .


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