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  • richardmitnick 6:19 am on August 24, 2018 Permalink | Reply
    Tags: , , , , MIT/Caltech Advanced aLIGO, ,   

    From The Conversation: “We’re going to get a better detector: time for upgrades in the search for gravitational waves” 

    From The Conversation

    August 16, 2018
    Robert Ward

    It’s been a year since ripples in space-time from a colliding pair of dead stars tickled the gravitational wave detectors of the Advanced LIGO and Advanced Virgo facilities.

    Soon after, astronomers around the world began a campaign to observe the afterglow of the collision of a binary neutron star merger in radio waves, microwaves, visible light, x-rays and more.

    See https://sciencesprings.wordpress.com/2017/10/16/from-ucsc-a-uc-santa-cruz-special-report-neutron-stars-gravitational-waves-and-all-the-gold-in-the-universe/

    This was the dawn of multi-messenger astronomy: a new era in astronomy, where events in the universe are observed with more than just a single type of radiation. In this case, the messengers were gravitational waves and electromagnetic radiation.

    What we’ve learned (so far)

    From this single event, we learned an incredible amount. Last October, on the day the detection was made public, 84 scientific papers were published (or the preprints made available).

    We learned that gravity and light travel at the same speed, neutron star mergers are a source of short gamma-ray bursts, and that kilonovae – the explosion from a neutron star merger – are where our gold comes from.

    This rich science came from the fact that we were able to combine our observatories to witness this single event from multiple astronomical “windows”. The gravitational waves arrived first, followed 1.7 seconds later by gamma-rays. That is a pretty small delay, considering the waves had been travelling for 130 million years.

    Over the next few weeks, visible light and radio waves began to be observed and then slowly faded.

    It seemed like the news about gravitational waves was coming fast and furious, with the first detection announced in 2016, a Nobel prize in 2017, and the announcement of the binary neutron star merger just weeks after the Nobel prize.

    Time for upgrades

    On this first anniversary of the neutron star merger, the gravitational wave detectors are offline for upgrades. They actually went offline shortly after the detection and will come back online some time early in 2019.

    The work of making gravitational wave detectors function requires extraordinary patience and dedication. These are exquisite experiments – it took more than 40 years of technological development by a community of more than a thousand scientists to get to the point of detecting the first signal.

    Naturally, improving on this work is not easy. So what does it actually take?

    We really do listen to gravitational waves, and our detectors act more like microphones than telescopes or cameras.

    Quiet please!

    To detect gravitational waves, we need to do more than just turn off the dishwasher. We need to build the quietest, best-isolated thing on Earth.

    Unfortunately, the laws of quantum mechanics and thermodynamics both prevent us from eliminating the noise entirely. Nonetheless, we strive to do the best that these fundamental limits permit. This involves, among many other extraordinary things, hanging our mirrors on glass threads .

    Before sealing up the chamber and pumping the vacuum system down, a LIGO optics technician inspects one of LIGO’s core optics (mirrors) by illuminating its surface with light at a glancing angle. Matt Heintze/Caltech/MIT/LIGO Lab

    Our mirrors weight 40kg each and are suspended from four of these glass threads, which are less than a half-millimetre in diameter and exquisitely crafted.

    The threads are under enormous stress, and the slightest imperfection (or the slightest touch) can cause them to explode.

    Just such an explosion happened earlier this year while installing a new mirror. Fortunately, the precious mirror fell into a cradle designed for just such a possibility, and was not damaged.

    Nonetheless, the delicate, intricate work of creating the glass threads, attaching them to the mirror, hanging the mirror and then installing it all needed to be redone.

    Improvements to the detector

    This was a heartbreaking setback for the team, but the added delay was not entirely in vain. In parallel with remaking the glass threads and rehanging the new mirror, we made some other improvements to the detector, for which we otherwise would not have had enough time.

    One of the goals of this upgrade period is to install something called a quantum squeezed light source into the gravitational wave detectors.

    As mentioned earlier, quantum mechanics mandates a certain minimum amount of noise in any measurement. We can’t arbitrarily reduce this quantum noise, but we can move it around and change its shape by squeezing it.

    This is a bit like sweeping dust under the rug. It’s not really gone, but it might not bother you so much anymore. The quantum squeezed light source does just this.

    Australian National University scientists Nutsinee Kijbunchoo and Terry McCrae build components for a quantum squeezed light source at LIGO Hanford Observatory in Washington, US. Nutsinee Kijbunchoo

    A gravitational wave detector is already a very complex system, and a squeezed light source is another complex system, so putting them together can be a challenge.

    Despite the complexity of this challenge, when the squeezed light source was activated for the first time at the LIGO detector in Livingston, Louisiana, US, in February this year there was an immediate improvement in the quantum noise: the gravitational wave detector output got just a bit quieter.

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

    See the full article here .


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    Our team of professional editors work with university and research institute experts to unlock their knowledge for use by the wider public.
    Access to independent, high quality, authenticated, explanatory journalism underpins a functioning democracy. Our aim is to promote better understanding of current affairs and complex issues. And hopefully allow for a better quality of public discourse and conversation.

  • richardmitnick 9:23 am on April 7, 2016 Permalink | Reply
    Tags: , , , MIT/Caltech Advanced aLIGO,   

    From phys.org: “LIGO researchers suggest background noise due to gravity waves may be much greater than thought” 


    April 7, 2016
    Bob Yirka

    MIT Caltech Advanced aLigo detector in Livingston, Louisiana
    MIT/Caltech Advanced aLigo detector in Livingston, Louisiana

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

    The research team working with the LIGO project has proposed that the data gleaned from the discovery of gravity waves last year allows for calculating the likely level of cosmic background noise due to gravitational waves, and that it is much greater than previous models have suggested. In their paper published in Physical Review Letters, researchers with the LIGO Scientific Collaboration along with a companion group from the Virgo Collaboration, describe their reasoning behind their estimates and why they believe they will be able to offer more support for their theory within just a few years.

    Prior to the landmark experiments that led to the detection of gravitational waves, researchers believed that there was likely a very nearly constant stream of background gravitational noise moving through the cosmos, generated by black holes and neutron stars merging, but had lacked any physical data that might allow them to estimate how much background noise might exist. With the detection of the gravitational waves that resulted from the merger of two binary black holes, the researchers suddenly found themselves with actual concrete data, which they have now used as a basis for calculating the likely amount of gravitational wave noise constantly bombarding our planet.

    To make predictions based on data from just one event, the team started with the assumption that the event that was measured was not one that was out of the ordinary—that allowed for making energy density estimates for all possible black hole binaries, based on the energy density of the black holes involved in the merger that was observed—and that in turn allowed for calculating estimates of the amount of gravitational radiation that would occur due to black holes merging. Next, they used the masses of the black holes that were observed to merge to calculate the likely true distribution regarding the number of black hole binaries in existence—this was possible because they placed the observed merger black holes in the middle of a bell curve. Doing so, the team reports, indicated that there are likely 20 times as many black hole binaries out there as has been estimated, which suggests that there is likely 10 times as much gravitational noise than has been suspected.

    The team acknowledges that because their results are based on a data from just one event, their conclusions could be wrong, but, if they are right, they note, they should be able to detect them within just the next five years or so as the LIGO and Virgo detectors grow to full strength.

    More information: B. P. Abbott et al. GW150914: Implications for the Stochastic Gravitational-Wave Background from Binary Black Holes, Physical Review Letters (2016). DOI: 10.1103/PhysRevLett.116.131102 , On Arxiv: http://arxiv.org/abs/1602.03847

    See the full article here .

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    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

  • richardmitnick 4:10 pm on April 6, 2016 Permalink | Reply
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    From Science Node: “LIGO and OSG peer into the Dark Energy Camera” 

    Science Node bloc
    Science Node

    06 Apr, 2016
    Greg Moore

    The Laser Interferometer Gravitational-wave Observatory (LIGO) gravitational wave announcement awaits corroborating observation. Using Open Science Grid (OSG) computing resources, they looked to the Dark Energy Camera images for visual evidence of the cosmic collision they detected.

    MIT/Caltech Advanced aLIGO Hanford Washington USA installation
    MIT/Caltech Advanced aLIGO Hanford Washington USA installation

    On September 14, 2015, gravitational waves were directly observed for the first time by both detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO). The detection confirmed Einstein’s proposal in his general theory of relativity. Now, scientists are seeking the wave source.

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

    Seeking the source

    While LIGO, funded by the US National Science Foundation (NSF), can pick out the general direction of the source of gravitational waves, it can’t identify the exact location. So, LIGO scientists are coordinating their measurements with observations made by the Dark Energy Camera (DECam) on the Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile.

    DECam, built at FNAL
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo

    Scientists at Fermilab and other institutions in the Dark Energy Survey use the camera to understand dark energy — a force scientists believe is helping the universe expand. A subset of members known as the Dark Energy Survey-Gravitational Wave (DES-GW) group are using the camera and the Open Science Grid (OSG) to build on LIGO’s groundbreaking findings.

    “Our focus primarily is the search for dark energy,” says Marcelle Soares-Santos, associate scientist at the US Department of Energy’s Fermilab. “Since we have experience detecting things through magnetic emissions, we coordinated with LIGO to find a source that we would find useful in our own research. Unfortunately this time we did not see anything, but we are now much better prepared when LIGO becomes active again later this year.”

    How to find a needle in a universe-sized haystack

    The area of sky DES-GW members observe is very large — 700 square degrees of sky, or about 2,800 times the size of the full moon — and requires rapid image processing. That’s where the OSG comes in. Without OSG, Soares-Santos says they couldn’t keep up.

    “For this event, we had something like 4-5,000 jobs. We must break every image down into smaller parts and process them in parallel on the OSG. It is critical to get our results fast — within 24 hours.”

    Scientists then analyze their observations with a spectrograph — which is expensive — so it’s important to narrow the choices down to only a few candidates. “At first, our turnaround time was not very fast, but thanks to our close partnership with the computing side here at Fermilab, now it is. We have great confidence that when LIGO observations start again in early August, we will be ready and hopefully see something.”

    Kenneth Herner, an application developer and systems analyst at Fermilab, is one of those key partners on the computing side. He makes sure the DES group has as many resources as they need and devotes part of his time to OSG.

    “Opportunistic OSG resources really help with the computing needs and the time crunch,” says Herner. “When we submit jobs, we get the first resources that meet the requirements no matter where they may be. We use the CernVM File System to pull in a code repository over HTTP to a local cache on a worker node. It only pulls down what it needs as it needs it. We don’t have to configure each OSG site — it just works. All OSG sites then look the same and all the site has to do is mount a repository.”

    In preparation for the LIGO partnership, Herner’s group prepared a code pipeline and made sure everything would work. The LIGO alert came on the 14th. “We had to wait on the telescope—and on top of that an earthquake in Chile,” says Herner. “We worked our plan, checked our code, transferred images from Chile up to the US, and submitted our jobs.”

    Almost all the jobs ran at Fermilab, but Herner says they could have gone anywhere on the OSG. “This was our shakedown cruise,” said Herner. “The first event used about 15,000 CPU hours for a full pass over all nights, but with multiple passes and preprocessing it was over 25,000 hours.” Without OSG resources, the group would have taken Fermilab computing resources away from other experiments, he says.

    Observing the sources of these gravitational waves will tell Soares-Santos how systems work and give her and her colleagues deeper insight into the physics. “It is quite challenging to observe these events,” says Soares-Santos.

    “We have to be quick to respond to see them. We have to be on the spot sooner and it is the computing that makes that possible. We couldn’t do it without the OSG because of the volume of data. We must have massive parallel computing and quick turnaround and hopefully next time we will see something exciting.”

    See the full article here .

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  • richardmitnick 11:09 am on March 30, 2016 Permalink | Reply
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    From ESA: “Integral sets limits on gamma rays from merging black holes” 

    ESA Space For Europe Banner

    European Space Agency

    30 March 2016

    Markus Bauer

    ESA Science Communication Officer

    Tel: +31 71 565 6799

    Mob: +31 61 594 3 954

    Email: markus.bauer@esa.int

    Volodymyr Savchenko
    François Arago Center
    APC – Astroparticule et Cosmologie
    Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire De Paris, Sorbonne Paris Cité
    Paris, France
    Email: savchenk@apc.in2p3.fr

    Carlo Ferrigno
    Integral Science Data Centre
    University of Geneva, Switzerland
    Email: Carlo.Ferrigno@unige.ch

    Erik Kuulkers
    ESA Integral Project Scientist
    Email: Erik.Kuulkers@esa.int

    Black holes merging Swinburne Astronomy Productions
    Black holes merging Swinburne Astronomy Productions
    Cornell SXS team. Two merging black holes simulation
    Cornell SXS team. Two merging black holes simulation

    Following the discovery of gravitational waves from the merging of two black holes, ESA’s Integral satellite has revealed no simultaneous gamma rays, just as models predict.


    On 14 September, the terrestrial Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves – fluctuations in the fabric of spacetime – produced by a pair of black holes as they spiralled towards each other before merging.

    MIT/Caltech Advanced aLIGO Hanford Washington USA installation
    MIT/Caltech Advanced aLIGO Hanford Washington USA installation

    The signal lasted less than half a second.

    The discovery was the first direct observation of gravitational waves, predicted by Albert Einstein a century ago.

    Two days after the detection, the LIGO team alerted a number of ground- and space-based astronomical facilities to look for a possible counterpart to the source of gravitational waves. The nature of the source was unclear at the time, and it was hoped that follow-up observations across the electromagnetic spectrum might provide valuable information about the culprit.

    Gravitational waves are released when massive bodies are accelerated, and strong emission should occur when dense stellar remnants such as neutron stars or black holes spiral towards each other before coalescing.

    Models predict that the merging of two stellar-mass black holes would not produce light at any wavelength, but if one or two neutron stars were involved in the process, then a characteristic signature should be observable across the electromagnetic spectrum.

    Another possible source of gravitational waves would be an asymmetric supernova explosion, also known to emit light over a range of wavelengths.

    It was not possible to pinpoint the LIGO source – its position could only be narrowed down to a very long strip across the sky.

    Observatories searched their archives in case data had been serendipitously collected anywhere along this strip around the time of the gravitational wave detection. They were also asked to point their telescopes to the same region in search for any possible ‘afterglow’ emission.

    Integral is sensitive to transient sources of high-energy emission over the whole sky, and thus a team of scientists searched through its data, seeking signs of a sudden burst of hard X-rays or gamma rays that might have been recorded at the same time as the gravitational waves were detected.

    “We searched through all the available Integral data, but did not find any indication of high-energy emission associated with the LIGO detection,” says Volodymyr Savchenko of the François Arago Centre in Paris, France. Volodymyr is the lead author of a paper reporting the results, published today in Astrophysical Journal Letters.

    The team analysed data from the Anti-Coincidence Shield on Integral’s SPI instrument. The shield helps to screen out radiation and particles coming from directions other than that where the instrument is pointing, as well as to detect transient high-energy sources across the whole sky.

    The team also looked at data from Integral’s IBIS instrument, although at the time it was not pointing at the strip where the source of gravitational waves was thought to be located.

    “The source detected by LIGO released a huge amount of energy in gravitational waves, and the limits set by the Integral data on a possible simultaneous emission of gamma rays are one million times lower than that,” says co-author Carlo Ferrigno from the Integral Science Data Centre at the University of Geneva, Switzerland.

    Subsequent analysis of the LIGO data has shown that the gravitational waves were produced by a pair of coalescing black holes, each with a mass roughly 30 times that of our Sun, located about 1.3 billion light years away. Scientists do not expect to see any significant emission of light at any wavelength from such events, and thus Integral’s null detection is consistent with this scenario.

    Similarly, nothing was seen by the great majority of the other astronomical facilities making observations from radio and infrared to optical and X-ray wavelengths.

    The only exception was the Gamma-Ray Burst Monitor on NASA’s Fermi Gamma-Ray Space Telescope, which observed what appears to be a sudden burst of gamma rays about 0.4 seconds after the gravitational waves were detected.

    NASA/Fermi Telescope
    NASA/Fermi Telescope

    The burst lasted about one second and came from a region of the sky that overlaps with the strip identified by LIGO.

    This detection sparked a bounty of theoretical investigations, proposing possible scenarios in which two merging black holes of stellar mass could indeed have released gamma rays along with the gravitational waves.

    However, if this gamma-ray flare had had a cosmic origin, either linked to the LIGO gravitational wave source or to any other astrophysical phenomenon in the Universe, it should have been detected by Integral as well. The absence of any such detection by both instruments on Integral suggests that the measurement from Fermi could be unrelated to the gravitational wave detection.

    “This result highlights the importance of synergies between scientists and observing facilities worldwide in the quest for as many cosmic messengers as possible, from the recently-detected gravitational waves to particles and light across the spectrum,” says Erik Kuulkers, Integral project scientist at ESA.

    This will become even more important when it becomes possible to observe gravitational waves from space. This has been identified as the goal for the L3 mission in ESA’s Cosmic Vision programme, and the technology for building it is currently being tested in space by ESA’s LISA Pathfinder mission.

    ESA/LISA Pathfinder
    ESA/LISA Pathfinder

    Such an observatory will be capable of detecting gravitational waves from the merging of supermassive black holes in the centres of galaxies for months prior to the final coalescence, making it possible to locate the source much more accurately and thus provide astronomical observatories with a place and a time to look out for associated electromagnetic emission.

    “We are looking forward to further collaborations and discoveries in the newly-inaugurated era of gravitational astronomy,” concludes Erik.

    Integral Upper Limits On Gamma-Ray Emission Associated With The Gravitational Wave Event GW150914, by V. Savchenko et al. is published in Astrophysical Journal Letters.

    The science team:
    V. Savchenko1, C. Ferrigno2, S. Mereghetti3, L. Natalucci4, A. Bazzano4, E. Bozzo2, S. Brandt5, T. J.-L. Courvoisier2, R. Diehl6, L. Hanlon7, A. von Kienlin6, E. Kuulkers8, P. Laurent9,10, F. Lebrun9, J. P. Roques11, P. Ubertini4, and G. Weidenspointner6,12

    Author affiliations

    1 François Arago Centre, APC, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cité, 10 rue Alice Domon et Léonie Duquet, F-75205 Paris Cedex 13, France

    2 ISDC, Department of astronomy, University of Geneva, chemin d’Écogia, 16 CH-1290 Versoix, Switzerland

    3 INAF, IASF-Milano, via E.Bassini 15, I-20133 Milano, Italy

    4 INAF-Institute for Space Astrophysics and Planetology, Via Fosso del Cavaliere 100, I-00133-Rome, Italy

    5 DTU Space—National Space Institute Elektrovej—Building 327 DK-2800 Kongens Lyngby, Denmark

    6 Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany

    7 Space Science Group, School of Physics, University College Dublin, Belfield, Dublin 4, Ireland

    8 European Space Astronomy Centre (ESA/ESAC), Science Operations Department E-28691, Villanueva de la Cañada, Madrid, Spain

    9 APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cité, 10 rue Alice Domont et Léonie Duquet, F-75205 Paris Cedex 13, France

    10 DSM/Irfu/Service d’Astrophysique, Bat. 709 Orme des Merisiers CEA Saclay, F-91191 Gif-sur-Yvette Cedex, France

    11 Université Toulouse; UPS-OMP; CNRS; IRAP; 9 Av. Roche, BP 44346, F-31028 Toulouse, France

    12 European XFEL GmbH, Albert-Einstein-Ring 19, D-22761, Hamburg, Germany

    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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