From AAS NOVA: “A Software Solution for Tracking Down Gravitational Wave Sources”

From AAS NOVA

9.9.22
Kerry Hensley

Gravitational waves. Credit: W.Benger-Zib. MPG Institute for Gravitational Physics (DE)

An illustration of two neutron stars approaching a merger. [L. Calçada/The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europaiche Sûdsternwarte] (EU)(CL)]

When racing to follow up on a new detection of gravitational waves, every second of telescope time is precious. A recent publication describes how a new algorithm for scheduling observations might improve our ability to track down transient events.

Seeking Gravitational Wave Sources

Locations of the observatories that followed up on the detection of the gravitational wave signal GW170817. [LIGO-Virgo]

Caltech/MIT Advanced aLigo at Hanford, WA, Livingston, LA; and VIRGO Gravitational Wave interferometer, near Pisa(IT).

The search for the source of gravitational wave event GW170817 is an amazing success story. In the days following the initial detection, telescopes across the world pinpointed and monitored the resulting kilonova, leading to a deep understanding of the event — but since then, no other gravitational wave source has been definitively identified.

Searches for gravitational wave sources are challenging because the search areas are often large, telescope time is limited, and the events are transient. How can we track down the causes of gravitational wave signals in a way that makes the most efficient use of the available observing time? In a recent publication, B. Parazin (Northeastern University and University of Minnesota) put a new observation-scheduling algorithm to the test.

Scheduling Telescope Time

Parazin and collaborators tested a new algorithm optimized for the Zwicky Transient Facility (ZTF), which is designed to detect transient events.

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

Caltech Palomar Samuel Oschin 48 inch Telescope, located in San Diego County, California, altitude 1712 m (5617 ft). Credit: Caltech.

The team aimed to maximize the odds of tracking down the source of a new gravitational wave signal while minimizing the amount of observing time needed. They also accounted for factors that are unique to the ZTF, such as the time needed to switch between filters.

In addition to the particulars of the ZTF observing setup, the algorithm takes as an input a map of the sky showing the probable locations of a gravitational wave source, which is released by gravitational wave observatories when a new signal is detected. From there, the algorithm identifies which out of the ZTF telescope’s 1,778 possible pointing directions are appropriate, groups pointings that are continuously observable during a selected length of time, and orders the pointings within each group so as to minimize the amount of time the telescope spends between observations.

Improving Efficiency

Comparison of the probability coverage of the existing algorithm in use by the ZTF (gwemopt) to that of the new algorithm introduced in this work (MUSHROOMS). The new algorithm performs better than the existing algorithm for cases located under the yellow line. [Parazin et al. 2022]

To compare the new algorithm to the one ZTF currently uses, the team scheduled observations with each method for 951 simulated detections of binary neutron star mergers. Under the conditions best suited to compare the two methods, Parazin and coauthors find that their new algorithm improves upon the existing software by 5.8%, on average — in other words, the new observing schedules increased the probability of finding the source. Since the existing algorithm sometimes outperformed the new algorithm, a hybrid approach — running both algorithms and choosing the more efficient solution — was the best, netting an average 8.1% improvement.

A final wrinkle is the fact that transient sources can fade rapidly, making the order in which the observations are carried out important — reach a source too late, and it may have dimmed beyond detection. When testing both algorithms on finding rapidly fading synthetic kilonovae, the team found that 1) once again, the hybrid approach had the best performance, and 2) the new algorithm had an advantage over the existing software when the search area was large.

Citation

Foraging with MUSHROOMS: A Mixed-integer Linear Programming Scheduler for Multimessenger Target of Opportunity Searches with the Zwicky Transient Facility, B. Parazin et al 2022 ApJ 935 87.
https://iopscience.iop.org/article/10.3847/1538-4357/ac7fa2/pdf

See the full article here .

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

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

Adopted June 7, 2009

The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

From The Kavli Institute for the Physics and Mathematics of the Universe (IPMU) [カブリ数物連携宇宙研](JP) at The University of Tokyo [東京大学](JP): “New theory finds upcoming satellite mission will be able to detect more than expected”

From The Kavli Institute for the Physics and Mathematics of the Universe (IPMU) [カブリ数物連携宇宙研](JP) at The University of Tokyo [東京大学](JP)

The upcoming satellite experiment LiteBIRD is expected to probe the physics of the very early Universe if the primordial inflation happened at high energies.

JAXA LiteBIRD Kavli IPMU

But now, a new paper in Physical Review Letters shows it can also test inflationary scenarios operating at lower energies.

The green line is the lowest signal the LiteBIRD can still observe, so any observable signal should be above that line. The red and black lines are the team’s predictions for two different parameter specifications in their model, showing detection is possible. In contrast, the more standard inflationary models operating at the same energy as the team’s mechanism predict the lower gray (dashed) line, which is below the sensitivity limit of LiteBIRD. (Credit: Cai et al.)

Cosmologists believe that in its very early stages, the Universe underwent a very rapid expansion called “cosmic inflation”.

_____________________________________________________________________________________
Inflation

Alan Guth, from M.I.T., who first proposed cosmic inflation.

Lamda Cold Dark Matter Accerated Expansion of The universe http scinotions.com the-cosmic-inflation-suggests-the-existence-of-parallel-universes. Credit: Alex Mittelmann.

Alan Guth’s notes:
Alan Guth’s original notes on inflation.
_____________________________________________________________________________________

A success story of this hypothesis is that even the simplest inflationary models are able to accurately predict the inhomogeneous distribution of matter in the Universe. During inflation, these vacuum fluctuations were stretched to astronomical scales, becoming the source all the structure in the Universe, including the Cosmic Microwave Background [CMB] anisotropies, distribution of Dark Matter and galaxies.

CMB per European Space Agency(EU) Planck.

The same mechanism also produced gravitational waves.

Gravitational waves. Credit: W.Benger-Zib. MPG Institute for Gravitational Physics (DE)

These gravitational wave propagating ripples of space and time are important for understanding the physics during the inflationary epoch. In general, detecting these gravitational waves is considered determining the energy at which inflation took place. It is also linked to how much the inflation field-or the energy source of inflation-can change during inflation — a relation referred to as the “Lyth bound”.

An artist’s conception of how gravitational waves distort the shape of space and time in the universe (Credit: Kavli IPMU).

The primordial gravitational waves generated from vacuum are extremely weak, and are very difficult to detect, but the JAXA-led LiteBIRD mission might be able to detect them via the polarization measurements of the Cosmic Microwave Background. Because of this, understanding primordial gravitational waves theoretically is gaining interest so any potential detection by LiteBIRD can be interpreted. It is expected LiteBIRD will be able to detect primordial gravitational waves if inflation happened at sufficiently high energies.

Several inflationary models constructed in the framework of quantum gravity often predict very low energy scale for inflation, and so would be untestable by LiteBIRD. However, a new study by researchers, including the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), has shown the opposite. The researchers argue such scenarios of fundamental importance can be tested by LiteBIRD, if they are accompanied by additional fields, sourcing gravitational waves.

The researchers suggest an idea, logically very different from the usual.

“Within our framework in addition to the gravitational waves originating from vacuum fluctuations, a large amount of gravitational waves can be sourced by the quantum vacuum fluctuations of additional fields during inflation. Due to this we were able to produce an observable amount of gravitational waves even if inflation takes place at lower energies.

“The quantum fluctuations of scalar fields during inflation are typically small, and such induced gravitational waves are not relevant in standard inflationary scenarios. However, if the fluctuations of the additional fields are enhanced, they can source a significant amount of gravitational waves,” said paper author and Kavli IPMU Project Researcher Valeri Vardanyan.

Other researchers have been working on related ideas, but so far no successful mechanism based on scalar fields alone had been found.

“The main problem is that when you generate gravitational waves from enhanced fluctuations of additional fields, you also simultaneously generate extra curvature fluctuations, which would make the Universe appear more clumpy than it is in reality. We elegantly decoupled the generation of the two types of fluctuations and solved this problem,” said Vardanyan.

In their paper, the researchers proposed a proof-of-concept based on two scalar fields operating during inflation.

“Imagine a car with two engines, corresponding to the two fields of our model. One of the engines is connected to the wheels of the car, while the other one is not. The first one is responsible for moving the car, and, when on a muddy road, for generating all the traces on the road. These represent the seeds of structure in the Universe. The second engine is only producing sound. This represents the gravitational waves, and does not contribute to the movement of the car, or the generation of traces on the road,” said Vardanyan.

The team quantitatively demonstrated their mechanism works, and even calculated the predictions of their model for the upcoming LiteBIRD mission.

See the full article here .

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The Kavli Institute for the Physics and Mathematics of the Universe (IPMU) [カブリ数物連携宇宙研](JP) at The University of Tokyo [東京大学](JP) is an international research institute with English as its official language. The goal of the institute is to discover the fundamental laws of nature and to understand the Universe from the synergistic perspectives of mathematics, astronomy, and theoretical and experimental physics. The Institute for the Physics and Mathematics of the Universe (IPMU) was established in October 2007 under the World Premier International Research Center Initiative (WPI) of the Ministry of Education, Sports, Science and Technology in Japan with the University of Tokyo as the host institution. IPMU was designated as the first research institute within the University of Tokyo Institutes for Advanced Study (UTIAS) in January 2011. It received an endowment from The Kavli Foundation and was renamed the “Kavli Institute for the Physics and Mathematics of the Universe” in April 2012. Kavli IPMU is located on the Kashiwa campus of the University of Tokyo, and more than half of its full-time scientific members come from outside Japan. http://www.ipmu.jp/

The Kavli Foundation, based in Oxnard, California, is dedicated to the goals of advancing science for the benefit of humanity and promoting increased public understanding and support for scientists and their work.

The Foundation’s mission is implemented through an international program of research institutes, professorships, and symposia in the fields of astrophysics, nanoscience, neuroscience, and theoretical physics as well as prizes in the fields of astrophysics, nanoscience, and neuroscience.

From Galician Institute of High Energy Physics (ES) and University of Aveiro [Universidade de Aveiro](PT) via phys.org: “Merging boson stars could explain massive black hole collision and prove existence of dark matter”

From Galician Institute of High Energy Physics (ES)

and

University of Aveiro [Universidade de Aveiro](PT)

Artistic impression of the merger of two boson stars. Credit: Nicolás Sanchis-Gual and Rocío García Souto.

An international team of scientists led by the Galician Institute of High Energy Physics (IGFAE) and the University of Aveiro [Universidade de Aveiro](PT) shows that the heaviest black hole collision ever observed, produced by the gravitational-wave GW190521, might actually be something even more mysterious: the merger of two boson stars. This would be the first evidence of the existence of these hypothetical objects which are a candidate for dark matter-believed to comprise 27% of the mass in the universe.

Gravitational waves are ripples in the fabric of spacetime that travel at the speed of light. These originate in the most violent events of in the universe, carrying information about their sources. Since 2015, the two LIGO detectors in the U.S. and the Virgo detector in Cascina, Italy, have detected and interpreted gravitational waves.

Caltech/MIT Advanced aLigo at Hanford, WA(US), Livingston, LA(US) and VIRGO Gravitational Wave interferometer, near Pisa(IT).

To date, these detectors have already observed around 50 gravitational-wave signals. All of these originated in the collisions and mergers of black holes and neutron stars, allowing physicists to deepen the knowledge about these objects.

Masses in the Stellar Graveyard GWTC-2 plot v1.0 BY LIGO-Virgo. Credit: Frank Elavsky and Aaron Geller at Northwestern University.

However, the promise of gravitational waves goes much further than this, as these should eventually provide us with evidence for previously unobserved and even unexpected objects, and shed light on current mysteries like the nature of dark matter. The latter may, however, have already happened.

In September 2020, the LIGO and Virgo collaboration (LVC) announced to the world the gravitational-wave signal GW190521. According to their analysis, the signal was consistent with the collision of two heavy black holes, of 85 and 66 times the mass of the sun, which produced a final black hole with 142 solar masses. The resulting black hole was the first of a new, previously unobserved black hole family: intermediate-mass black holes. This discovery is of paramount importance, as such black holes were the missing link between two well-known black-hole families: stellar-mass black holes that form from the collapse of stars, and supermassive black holes that reside in the center of almost every galaxy, including the Milky Way.

In addition, this observation came with an enormous challenge. If what we think we know about how stars live and die is correct, the heaviest of the colliding black holes (85 solar masses) could not form from the collapse of a star at the end of its life, which opens up a range of doubts and possibilities about its origins.

In an article published today in Physical Review Letters, a team of scientists lead by Dr. Juan Calderón Bustillo at the Galician Institute of High Energy Physics (IGFAE), joint center of the University of Santiago de Compostela and Xunta de Galicia, and Dr. Nicolás Sanchis-Gual, a postdoctoral researcher at the University of Aveiro and the Instituto Superior Técnico at University of Lisbon [Universidade de Lisboa](PT] , together with collaborators from University of Valencia [Universitat de València [univeɾsiˈtad de vaˈlensia]](ES), Monash University(AU) and The Chinese University of Hong Kong [香港中文大学; Xiānggǎng zhōngwén dàxué](HK), has proposed an alternative explanation for the origin of the signal GW190521: the collision of two exotic objects known as boson stars, which are one of the most likely candidates to explain dark matter. In their analysis, the team was able to estimate the mass of a new particle constituent of these stars, an ultra-light boson with a mass billions of times smaller than electrons.

The team compared the GW190521 signal to computer simulations of boson-star mergers, and found that these actually explain the data slightly better than the analysis conducted by LIGO and Virgo. The result implies that the source would have different properties than stated earlier. Dr. Calderón Bustillo says, “First, we would not be talking about colliding black holes anymore, which eliminates the issue of dealing with a ‘forbidden’ black hole. Second, because boson star mergers are much weaker, we infer a much closer distance than the one estimated by LIGO and Virgo. This leads to a much larger mass for the final black hole, of about 250 solar masses, so the fact that we have witnessed the formation of an intermediate-mass black hole remains true.”

Dr. Nicolás Sanchis-Gual says, “Boson stars are objects almost as compact as black holes but, unlike them, do not have a ‘no-return’ surface. When they collide, they form a boson star that can become unstable, eventually collapsing to a black hole, and producing a signal consistent with what LIGO and Virgo observed. Unlike regular stars, which are made of what we commonly know as matter, boson stars are made up of what we know as ultralight bosons. These bosons are one of the most appealing candidates for constituting what we know as dark matter.”

The team found that even though the analysis tends to favor the merging black-holes hypothesis, a boson star merger is actually preferred by the data, although in a non-conclusive way. Prof. Jose A. Font from the University of Valencia says, “Our results show that the two scenarios are almost indistinguishable given the data, although the exotic boson star hypothesis is slightly preferred. This is very exciting, since our boson-star model is, as of now, very limited, and subject to major improvements. A more evolved model may lead to even larger evidence for this scenario and would also allow us to study previous gravitational-wave observations under the boson-star merger assumption.”

This result would not only involve the first observation of boson stars but also that of their building block: a new particle known as an ultra-light boson. Prof. Carlos Herdeiro from University of Aveiro says, “One of the most fascinating results is that we can actually measure the mass of this putative new dark-matter particle, and that a value of zero is discarded with high confidence. If confirmed by subsequent analysis of this and other gravitational-wave observations, our result would provide the first observational evidence for a long-sought dark matter candidate.”

See the full article here.

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The Galician Institute of High Energy Physics (Instituto Galego de Física de Altas Enerxías, IGFAE) is a joint research center of University of Santiago de Compostela – USC [Universidade de Santiago de Compostela](ES) and Xunta de Galicia (the Galician Autonomous Government), that it was officially created on July 2, 1999.

Our main goal is to coordinate and foster the scientific and technical research in the field of High Energy Physics, Particle and Nuclear Physics and related areas as Astrophysics, Medical Physics and Instrumentation.

Of primary importance is the planning and promotion of the relation with large experimental facilities, especially with CERN, GSI/FAIR, Pierre Auger Observatory and LIGO at present.

In 2016, IGFAE was accredited “María de Maeztu” Unit of Excellence, integrating the Severo Ochoa and María de Maeztu alliance (SOMMa). This program of the Spanish Ministry of Science, Innovation and Universities identify and promote excellence in existing cutting-edge research institutions.

From U Wisconsin IceCube Collaboration: “IceCube pipeline responds quickly to transient phenomena reported by other observatories”

U Wisconsin ICECUBE neutrino detector at the South Pole, elevation of 2,835 metres (9,301 feet)

From U Wisconsin IceCube Collaboration

09 Dec 2020
Madeleine O’Keefe

The IceCube Neutrino Observatory, an array of over 5,000 light sensors embedded in a cubic-kilometer of ice at the South Pole, was built to detect astrophysical neutrinos: mysterious and nearly massless particles that carry information about the most energetic events in the cosmos. Every time IceCube sees something that might be a cosmic neutrino, it sends an alert to a network of telescopes and observatories around the world and in space, telling them to turn and look at that same spot in the sky. These other instruments see the universe in different ways; many detect photons of different wavelengths, from radio waves to gamma rays, while others detect different “messengers” entirely, like gravitational waves or neutrinos. Together, detections from different messengers give us a more complete picture of the cosmos.

The study of the universe with multiple channels—a field known as multimessenger astronomy—is valuable for investigating a number of questions, including learning about the sources of astrophysical neutrinos, one of IceCube’s main scientific goals. So rather than just waiting for neutrinos to come to IceCube, IceCube can also follow up on detections made by other telescopes. And since IceCube can observe the entire sky simultaneously and is “on” more than 99 percent of the time, it can provide unique and valuable insight for other observatories.

Since 2016, the IceCube Collaboration has used a fast-response analysis pipeline to perform follow-up neutrino searches on interesting detections in other messengers that might have neutrino counterparts. As of July 2020, the pipeline led to 58 analyses, none of which found significant neutrino signals but enabled researchers to constrain neutrino emission from some potential sources. The collaboration described their results in a paper recently submitted to The Astrophysical Journal.

Results of IceCube’s follow-up for the gamma-ray burst GRB190114C, one of the only GRBs to ever be detected by a ground-based gamma-ray telescope. This plot shows the flux as a function of energy, where blue tones are results from various wavelengths of light, from X-rays (left) to very high energy gamma rays (right). The upper limit on the high-energy neutrino flux, one of the results reported in the paper, is shown by the solid magenta line. Credit: IceCube Collaboration.

“The motivation for this analysis is to take the idea of neutrino alerts and turn it on its head,” says Alex Pizzuto, a doctoral student at the University of Wisconsin–Madison and a lead on this analysis. “Instead of sending out interesting neutrinos to the community and letting observers follow up on our events, we take interesting events reported in other messengers, like photons, and check to see if there are neutrinos coming from the same object. And we do it all in real time.”

Pizzuto and his collaborators have been doing this since 2016 when they established a fast-response analysis pipeline. The pipeline monitors various channels where astronomers announce interesting observations (such as the Gamma-ray Coordinates Network and the The Astronomer’s Telegram) and identifies potentially interesting detections. Then, IceCube researchers evaluate whether the target is a viable neutrino emitter and whether it would be useful for IceCube to check it out. If yes, the researchers determine a time frame around the event of interest and use the pipeline to rapidly perform a statistical analysis of IceCube data to see if any neutrino candidate events correlate with the target in time and direction. When the analysis is complete, the researchers send out their results via the same channels they were monitoring in the first place.

As of July 2020, the pipeline has led to 58 analyses, none of which found a statistically significant signal of neutrinos. But the researchers were able to use the pipeline to put constraints on some of the source classes they studied, including fast radio bursts, extreme blazar flares, bright gamma-ray bursts, and gravitational waves. Pizzuto says that they are already seeing some of their limits incorporated into models of potential neutrino sources.

“Unlike most telescopes, IceCube observes the entire sky (including both hemispheres), all the time (including both day and night),” according to Justin Vandenbroucke, a UW–Madison physics professor and another lead on the paper. “So whenever a new astrophysical transient event is reported by another observatory, we know IceCube was also looking there then. Our pipeline enables us to rapidly search for neutrinos and report the results. This real-time approach to multimessenger astrophysics has enabled the key discoveries of the field so far, and will continue to in the future.”

Looking ahead, the researchers plan to continue running the pipeline. They hope that this analysis will identify a multimessenger source in the future. In the meantime, they are studying a variety of source classes with this tool. And there is a plan to use this pipeline to search for additional neutrinos coming from the same directions as the high-energy neutrinos that trigger IceCube alerts.

See the full article here .

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IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

IceCube neutrino detector interior.

IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

Lunar Icecube

IceCube DeepCore annotated

IceCube PINGU annotated

DM-Ice II at IceCube annotated

U Wisconsin IceCube Gen2 facility

From Science News: “A new gravitational wave detector is almost ready to join the search”

From Science News

January 18, 2019
Emily Conover

Japan’s KAGRA experiment tests new techniques for spotting ripples in spacetime.

KAGRA gravitational wave detector, Kamioka mine in Kamioka-cho, Hida-city, Gifu-prefecture, Japan

KAGRA tunnel

In the quest for better gravitational wave detectors, scientists are going cold.

An up-and-coming detector called KAGRA aims to spot spacetime ripples by harnessing advanced technological twists: chilling key components to temperatures hovering just above absolute zero, and placing the ultrasensitive setup in an enormous underground cavern.

Scientists with KAGRA, located in Kamioka, Japan, now have results from their first ultrafrigid tests. Those experiments suggest that the detector should be ready to start searching for gravitational waves later in 2019, the team reports January 14 at arXiv.org.

The new detector will join similar observatories in the search for the minute cosmic undulations, which are stirred up by violent events like collisions of black holes. The Laser Interferometer Gravitational-Wave Observatory, LIGO, has two detectors located in Hanford, Wash., and Livingston, La. Another observatory, Virgo, is located near Pisa, Italy.

VIRGO Gravitational Wave interferometer, near Pisa, Italy

Caltech/MIT Advanced aLigo Hanford, WA, USA installation

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

Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

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

ESA/eLISA the future of gravitational wave research

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

Those detectors sit above ground, and don’t use the cooling technique, making KAGRA the first of its kind.

KAGRA consists of two 3-kilometer-long arms, arranged in an “L” shape. Within each arm, laser light bounces back and forth between two mirrors located at both ends. The light acts like a giant measuring stick, capturing tiny changes in the length of each arm, which can be caused by a passing gravitational wave stretching and squeezing spacetime.

FREEZE UP KAGRA’s mirrors (one shown) are cooled to very low temperatures to prevent jiggling that could hamper the search for gravitational waves.

Because gravitational wave detectors measure length changes tinier than the diameter of a proton, minuscule effects like the jiggling of molecules on the mirrors’ surfaces can interfere with the measurements. Cooling the mirrors to about 20 kelvins (–253° Celsius) limits that jiggling.

In the new tests, performed in spring 2018, researchers cooled only one of KAGRA’s four mirrors, says KAGRA leader Takaaki Kajita of the University of Tokyo. When the detector starts up for real, the others will be chilled too.

Having the detector underground also helps keep the mirrors from vibrating due to activity on Earth’s surface. LIGO is so sensitive that it can be affected by rumbling trucks, a stiff breeze or even mischievous wildlife (SN Online: 4/18/18). KAGRA’s underground lair should be significantly quieter.

Building underground and going cold required years of effort from KAGRA’s researchers. “They’ve taken on these two great challenges, which are both important to the long-term future of the field,” says LIGO spokesperson David Shoemaker of MIT. In the future, even more advanced gravitational wave detectors could build on KAGRA’s techniques.

For now, adding KAGRA to the existing observatories should help scientists improve their studies of where gravitational wiggles come from. Once scientists detect a gravitational wave signal, they alert astronomers, who search for light from the cataclysm that generated the waves in the hope of better understanding the event (SN: 11/11/17, p. 6). Having an additional gravitational wave detector in a different part of the world will help better triangulate wave sources. “This feature is very important,” Kajita says, “because telescopes can only see a small part of the sky at a time.”

See the full article here .

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From MIT Caltech Advanced aLIGO: “LIGO and Virgo Announce Four New Detections”

From MIT Caltech Advanced aLIGO

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LIGO-Virgo/Frank Elavsky/Northwestern

The observatories are also releasing their first catalog of gravitational-wave events.

On Saturday, December 1, scientists attending the Gravitational Wave Physics and Astronomy Workshop in College Park, Maryland, presented new results from the National Science Foundation’s LIGO (Laser Interferometer Gravitational-Wave Observatory) and the European- based VIRGO gravitational-wave detector regarding their searches for coalescing cosmic objects, such as pairs of black holes and pairs of neutron stars. The LIGO and Virgo collaborations have now confidently detected gravitational waves from a total of 10 stellar-mass binary black hole mergers and one merger of neutron stars, which are the dense, spherical remains of stellar explosions. Six of the black hole merger events had been reported before, while four are newly announced.

From September 12, 2015, to January 19, 2016, during the first LIGO observing run since undergoing upgrades in a program called Advanced LIGO, gravitational waves from three binary black hole mergers were detected. The second observing run, which lasted from November 30, 2016, to August 25, 2017, yielded one binary neutron star merger and seven additional binary black hole mergers, including the four new gravitational-wave events being reported now. The new events are known as GW170729, GW170809, GW170818, and GW170823, in reference to the dates they were detected.

All of the events are included in a new catalog, also released Saturday, with some of the events breaking records. For instance, the new event GW170729, detected in the second observing run on July 29, 2017, is the most massive and distant gravitational-wave source ever observed. In this coalescence, which happened roughly 5 billion years ago, an equivalent energy of almost five solar masses was converted into gravitational radiation.

GW170814 was the first binary black hole merger measured by the three-detector network, and allowed for the first tests of gravitational-wave polarization (analogous to light polarization).

The event GW170817, detected three days after GW170814, represented the first time that gravitational waves were ever observed from the merger of a binary neutron star system. What’s more, this collision was seen in gravitational waves and light, marking an exciting new chapter in multi-messenger astronomy, in which cosmic objects are observed simultaneously in different forms of radiation.

One of the new events, GW170818, which was detected by the global network formed by the LIGO and Virgo observatories, was very precisely pinpointed in the sky. The position of the binary black holes, located 2.5 billion light-years from Earth, was identified in the sky with a precision of 39 square degrees. That makes it the next best localized gravitational-wave source after the GW170817 neutron star merger.

Caltech’s Albert Lazzarini, Deputy Director of the LIGO Laboratory, says “The release of four additional binary black hole mergers further informs us of the nature of the population of these binary systems in the universe and better constrains the event rate for these types of events.”

“In just one year, LIGO and VIRGO working together have dramatically advanced gravitational- wave science, and the rate of discovery suggests the most spectacular findings are yet to come,” says Denise Caldwell, Director of NSF’s Division of Physics. “The accomplishments of NSF’s LIGO and its international partners are a source of pride for the agency, and we expect even greater advances as LIGO’s sensitivity becomes better and better in the coming year.”

“The next observing run, starting in Spring 2019, should yield many more gravitational-wave candidates, and the science the community can accomplish will grow accordingly,” says David Shoemaker, spokesperson for the LIGO Scientific Collaboration and senior research scientist in MIT’s Kavli Institute for Astrophysics and Space Research. “It’s an incredibly exciting time.”

“It is gratifying to see the new capabilities that become available through the addition of Advanced Virgo to the global network,” says Jo van den Brand of Nikhef (the Dutch National Institute for Subatomic Physics) and VU University Amsterdam, who is the spokesperson for the Virgo Collaboration. “Our greatly improved pointing precision will allow astronomers to rapidly find any other cosmic messengers emitted by the gravitational-wave sources.” The enhanced pointing capability of the LIGO-Virgo network is made possible by exploiting the time delays of the signal arrival at the different sites and the so-called antenna patterns of the interferometers.

“The new catalog is another proof of the exemplary international collaboration of the gravitational wave community and an asset for the forthcoming runs and upgrades”, adds EGO Director Stavros Katsanevas.

The scientific papers describing these new findings, which are being initially published on the arXiv repository of electronic preprints, present detailed information in the form of a catalog of all the gravitational wave detections and candidate events of the two observing runs as well as describing the characteristics of the merging black hole population. Most notably, we find that almost all black holes formed from stars are lighter than 45 times the mass of the Sun. Thanks to more advanced data processing and better calibration of the instruments, the accuracy of the astrophysical parameters of the previously announced events increased considerably.

Laura Cadonati, Deputy Spokesperson for the LIGO Scientific Collaboration, says “These new discoveries were only made possible through the tireless and carefully coordinated work of the detector commissioners at all three observatories, and the scientists around the world responsible for data quality and cleaning, searching for buried signals, and parameter estimation for each candidate — each a scientific specialty requiring enormous expertise and experience.”

Related Links

Paper: “GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs”

Paper: “Binary Black Hole Population Properties Inferred from the First and Second Observing Runs of Advanced LIGO and Advanced Virgo”

The Collaborations

LIGO is funded by NSF and operated by Caltech and MIT, which conceived of LIGO and led the Initial and Advanced LIGO projects. Financial support for the Advanced LIGO project was led by the NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council-OzGrav) making significant commitments and contributions to the project. More than 1,200 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration. A list of additional partners is available at https://my.ligo.org/census.php.

The Virgo collaboration consists of more than 300 physicists and engineers belonging to 28 different European research groups: six from Centre National de la Recherche Scientifique (CNRS) in France; 11 from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; two in the Netherlands with Nikhef; the MTA Wigner RCP in Hungary; the POLGRAW group in Poland; Spain with IFAE and the Universities of Valencia and Barcelona; two in Belgium with the Universities of Liege and Louvain; Jena University in Germany; and the European Gravitational Observatory (EGO), the laboratory hosting the Virgo detector near Pisa in Italy, funded by CNRS, INFN, and Nikhef. A list of the Virgo Collaboration can be found at http://public.virgo-gw.eu/the-virgo-collaboration/. More information is available on the Virgo website at http://www.virgo-gw.eu.

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VIRGO Gravitational Wave interferometer, near Pisa, Italy

Caltech/MIT Advanced aLigo Hanford, WA, USA installation

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

Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

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

ESA/eLISA the future of gravitational wave research

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

From U Wisconsin IceCube Collaboration: “Multimessenger searches for sources of gravitational waves and neutrinos”

U Wisconsin ICECUBE neutrino detector at the South Pole

IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

Lunar Icecube

IceCube DeepCore annotated

IceCube PINGU annotated

DM-Ice II at IceCube annotated

From From U Wisconsin IceCube Collaboration

09 Nov 2018
Sílvia Bravo

Artist’s now iconic illustration of two merging neutron stars. The rippling space-time grid represents gravitational waves that travel out from the collision, while the narrow beams show the bursts of gamma rays and neutrinos that are shot out just seconds after the gravitational waves. Image: NSF/LIGO/Sonoma State University/A. Simonnet

Last year was an extraordinary year for multimessenger astrophysics. In August 2017, a gravitational wave and its electromagnetic counterpart emission were detected from a pair of inspiraling neutron stars. Only a month later, a high-energy neutrino was detected at the South Pole and electromagnetic follow-up observations helped identify the first likely source of very high energy neutrinos and cosmic rays.

Since then, the dream of astrophysicists has been to join neutrinos and gravitational waves in the detection of a multimessenger source. According to our understanding of the extreme universe, a possible scenario would be a neutrino created in the relativistic outflows of a merger of binary neutron stars or black holes or the core-collapse of a supernova, all cataclysmic cosmic environments that should also produce gravitational waves.

The IceCube, LIGO, Virgo, and ANTARES collaborations have used data from the first observing period of Advanced LIGO and from the two neutrino detectors to search for coincident neutrino and gravitational wave emission from transient sources.

The goal was to explore the discovery potential of a multimessenger observation, i.e., of a source detection that needs both messengers to confirm its astrophysical origin. Scientists did not find any significant coincidence. The results, recently submitted to The Astrophysical Journal, set a constraint on the density of these sources.

The detection of gravitational waves and neutrinos from a single source would set a new milestone in multimessenger astronomy, allowing the simultaneous study of the inner and outer processes powering high-energy emission from astrophysical objects.

A joint detection would also significantly improve the localization of the source and enable faster and more precise electromagnetic follow-up observations. The scrutiny of an astrophysical source with three different messengers would not only be the next breakthrough in the field but would also confirm that multimessenger astronomy is the only path to a profound understanding of the extreme universe.

Even though the current search was very limited in time, researchers have set a strong constraint for joint emission from core-collapse supernovas, while binary mergers remain secure as potential multimessenger sources of gravitational waves and high-energy neutrinos.

This study used datasets, spanning less than 2.5 months, that are also limited by LIGO’s sensitivity, which will soon improve by a factor of 2. The addition of new LIGO and Virgo data as well as from IceCube and ANTARES will greatly increase the sensitivity of joint searches. In the longer term, future next-generation neutrino and gravitational wave detectors will boost the potential of discovery for these searches.

See the full article here .

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IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

From AAS NOVA: ” Two Explosions with Similar Quirks”

From AAS NOVA

12 October 2018
Susanna Kohler

Artist’s by now iconic illustration of the merger of two neutron stars, producing a short gamma-ray burst. [NSF/LIGO/Sonoma State University/A. Simonnet]

High-energy radiation released during the merger of two neutron stars last year has left astronomers puzzled. Could a burst of gamma rays from 2015 help us to piece together a coherent picture of both explosions?

A Burst Alone?

When two neutron stars collided last August, forming a distinctive gravitational-wave signal and a burst of radiation detected by telescopes around the world, scientists knew that these observations would change our understanding of short gamma-ray bursts (GRBs).Though we’d previously observed thousands of GRBs, GRB 170817A was the first to have such a broad range of complementary observations — both in gravitational waves and across the electromagnetic spectrum — providing insight into its origin.

Total isotropic-equivalent energies for Fermi-detected gamma-ray bursts with known redshifts. GRB 170817A (pink star) is a factor of ~1,000 dimmer than typical short GRBs (orange points). GRB 170817A and GRB 150101B (green star) are two of the closest detected short GRBs. [Adapted from Burns et al. 2018]

But it quickly became evident that GRB 170817A was not your typical GRB. For starters, this burst was unusually weak, appearing 1,000 times less luminous than a typical short GRB. Additionally, the behavior of this burst was unusual: instead of having only a single component, the ~2-second explosion exhibited two distinct components — first a short, hard (higher-energy) spike, and then a longer, soft (lower-energy) tail.

The peculiarities of GRB 170817A prompted a slew of models explaining its unusual appearance. Ultimately, the question is: can our interpretations of GRB 170817A safely be applied to the general population of gamma-ray bursts? Or must we assume that GRB 170817A is a unique event, not representative of the general population?

New analysis of a GRB from 2015 — presented in a recent study led by Eric Burns (NASA Goddard SFC) — may help to answer this question.

A Matter of Angles

What does a burst from 2015 have to do with the curious case of GRB 170817A? Burns and collaborators have demonstrated that this 2015 burst, GRB 150101B, exhibited the same strange behavior as GRB 170817A: its emission can be broken down into two components consisting of a short, hard spike, followed by a long, soft tail. Unlike GRB 170817A, however, GRB 150101B is not underluminous — and it lasted less than a tenth of the time.

Fermi count rates in different energy ranges showing the short hard spike and the longer soft tail in GRB 150101B. The short hard spike is visible above 50 keV (top and middle panels). The soft tail is visible in the 10–50 keV channel (bottom panel). [Burns et al. 2018]

Intriguingly, these similarities and differences can all be explained by a single model. Burns and collaborators propose that GRB 150101B and GRB 170817A exhibit the exact same two-component behavior, and their differences in luminosity and duration can be explained by quirks of special relativity.

High-speed outflows such as these will have different apparent luminosities and durations depending on whether we view them along their axis or slightly from the side. Burns and collaborators demonstrate that these the two bursts could easily have the same profile — but GRB 150101B was viewed nearly on-axis, whereas GRB 170817A was viewed from an angle.

If this is true, then perhaps more GRBs have hard spikes and soft tails similar to these two; the tails may just be difficult to detect in more distant bursts. While more work remains to be done, the recognition that GRB 170817A may not be unique is an important one for understanding both its behavior and that of other short GRBs.

Citation

“Fermi GBM Observations of GRB 150101B: A Second Nearby Event with a Short Hard Spike and a Soft Tail,” E. Burns et al 2018 ApJL 863 L34.
http://iopscience.iop.org/article/10.3847/2041-8213/aad813/meta

VIRGO Gravitational Wave interferometer, near Pisa, Italy

Caltech/MIT Advanced aLigo Hanford, WA, USA installation

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

Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

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

ESA/eLISA the future of gravitational wave research

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

NASA/Fermi LAT

NASA/Fermi Gamma Ray Space Telescope

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AAS Mission and Vision Statement

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

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

Adopted June 7, 2009

From Caltech: “Superfast Jet Observed Streaming Away from Stellar Collision”

From Caltech

09/05/2018
Elise Cutts

An artist’s impression of the jet (pictured as a ball of fire), produced in the neutron star merger first detected on August 17, 2017 by telescopes around the world, as well as LIGO, which detects gravitational waves (green ripples). Credit: James Josephides (Swinburne University of Technology, Australia)

Using a collection of National Science Foundation radio telescopes, researchers have confirmed that a narrow jet of material was ejected at near light speeds from a neutron star collision. The collision, which was observed August 17, 2017 and occurred 130 million miles from Earth, initially produced gravitational waves that were observed by the Laser Interferometry Gravitational-wave Observatory (LIGO), alongside a flood of light in the form of gamma rays, X-rays, visible light, and radio waves. It was the first cosmic event to be observed in both gravitational waves and light waves.

Confirmation that a superfast jet had been produced by the neutron star collision came after radio astronomers discovered that a region of radio emission created by the merger had moved in a seemingly impossible way that only a jet could explain. The radio observations were made using the Very Long Baseline Array (VLBA), the Robert C. Byrd Green Bank Telescope (GBT), and the Very Large Array (VLA). The VLA is operated by the National Radio Astronomy Observatory (NRAO), which is closely associated with the other two telescopes involved in the discovery.

NRAO VLBA

GBO radio telescope, Green Bank, West Virginia, USA

NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

“We measured an apparent motion that is four times faster than light. That illusion, called superluminal motion, results when the jet is pointed nearly toward Earth and the material in the jet is moving close to the speed of light,” says Kunal Mooley, a Caltech postdoctoral scholar with a joint appointment at the NRAO and lead author of a new study about the jet appearing online September 5 in the journal Nature. Mooley and Assistant Professor of Astronomy Gregg Hallinan were part of an international collaboration that observed and interpreted the movement of the radio emission.

“We were lucky to be able to observe this event, because if the jet had been pointed too much farther away from Earth, the radio emission would have been too faint for us to detect,” says Hallinan.

Superfast jets are known to give rise to intense, short-duration gamma-ray bursts or sGRBs, predicted by theorists to be associated with neutron star collisions. The observation of a jet associated with this collision is therefore an important confirmation of theoretical expectations.

Superfast jets are known to give rise to intense, short-duration gamma-ray bursts or sGRBs, predicted by theorists to be associated with neutron star collisions. The observation of a jet associated with this collision is therefore an important confirmation of theoretical expectations.

The aftermath of the merger is now also better understood: the jet likely interacted with surrounding debris, forming a broad “cocoon” of material that expanded outward and accounted for the majority of the radio signal observed soon after the collision. Later on, the observed radio emission came mainly from the jet.

Read the full story from NRAO at https://public.nrao.edu/news/superfast-jet-neutron-star-merger/.

See the full article here .
See also 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/

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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.”

Caltech campus

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

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The Conversation US launched as a pilot project in October 2014. It is an independent source of news and views from the academic and research community, delivered direct to the public.
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