# Where can I watch the announcement from LIGO about gravitational waves?

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Today the LIGO consortium are having a press conference to update us on their search for gravitational waves. How should I watch the announcement?

The will also be tweeting: https://twitter.com/ligo

A video of the conference will also be available afterwards if you miss it. It starts at 10:30 EST, which is 3:30 GMT.

This is the easiest place: https://www.youtube.com/user/VideosatNSF/live, or alternatively it will probably be on most news websites.

## LIGO announcement vaults astronomy out of its silent movie era into the talkies

Chad Hanna receives funding from the National Science Foundation and the Charles E. Kaufman Foundation of The Pittsburgh Foundation.

### Partners

Penn State provides funding as a founding partner of The Conversation US.

The Conversation UK receives funding from these organisations

When LIGO detected its first gravitational wave back in September 2015, I was pretty excited to say the least. As part of a decades-long endeavor, our whole team was ecstatic to observe gravitational waves – which are literally ripples in space – caused by two black holes smashing together. It was the first time that Einstein’s predictions about these tiny ripples were directly confirmed. Just this month, the Nobel Prize in physics was awarded to three of the founders of our international collaborative effort – Rainer Weiss, Kip Thorne and Barry Barish – in recognition of this first observation.

It may be hard to believe, but today I am even more excited than I was in 2015. For the first time ever, astrophysicists have discovered gravitational waves originating from an entirely new source: merging neutron stars.

That’s not all. This new event, GW170817, was accompanied by a host of other observations across the electromagnetic spectrum including gamma-rays, X-rays, visible light and radio waves. Before, we had detected only gravitational waves on their own, without any other corroborating observations of the source event. This groundbreaking announcement from the LIGO Scientific Collaboration and the Virgo collaboration heralds the beginning of a new era in “multi-messenger” astronomy.

Various telescopes are focused on different energy wavelengths along the electromagnetic spectrum. NASA/CXC, CC BY

Until gravitational waves were discovered, astronomy was essentially in its silent film era. Gravitational waves provide something like a long-awaited soundtrack for our universe. The 2015 breakthrough and subsequent gravitational wave observations never managed to synchronize the sights and sounds of the cosmos, though. That changed with the detection of GW170817. Today we celebrate astronomy’s version of “the talkie” with the simultaneous observation of gravitational waves and electromagnetic radiation from the same source.

## OSU leading $17M effort to understand universe through low-frequency gravitational waves OSU Graphic produced by Tanka Klein and provided by the National Science Foundation depicts the search for low-frequency gravitational waves CORVALLIS, Ore. (KTVZ) – Oregon State University is the lead institution for a$17 million National Science Foundation center devoted to pushing the boundaries of physics knowledge by studying the universe through low-frequency gravitational waves, ripples in the fabric of time-space.

Funded by the NSF as a Physics Frontiers Center, the North American Nanohertz Observatory for Gravitational Waves, or NANOGrav, research group at OSU operates under the direction of Xavier Siemens, professor of physics in the OSU College of Science.

Siemens, who joined the Oregon State faculty in 2019, previously directed the NANOGrav Physics Frontier Center at the University of Wisconsin-Milwaukee, where it launched in 2015 with a $14.5 million award from the NSF. The new five-year grant is a renewal co-directed by Siemens and Maura McLaughlin, an astronomer at West Virginia University. It will help fund a collaboration of roughly 200 astrophysics researchers at 18 universities, including OSU’s Davide Lazzati and approximately 20 graduate and undergraduate students at Oregon State. OSU will receive about$600,000 annually, Siemens said.

Gravitational waves were first directly observed, by the Laser Interferometer Gravitational-Wave Observatory, in September 2015, a milestone event in physics and astronomy that confirmed one of the main predictions of Albert Einstein’s 1915 general theory of relativity.

Researchers detected those gravitational waves, produced by the collision of two black holes, using the twin LIGO interferometers in Livingston, Louisiana, and Hanford, Washington. Gravitational waves detected by LIGO, created by those types of “black hole binaries,” have frequencies of about 100 hertz, or 100 cycles per second, Siemens said. LIGO is an NSF-funded international collaboration.

“We’re searching for gravitational waves with frequencies 11 orders of magnitude below those LIGO is detecting,” he said. “We use, instead of lasers and mirrors at the end of vacuum tubes, radio pulsars and radio telescopes. We can use those pulsars as clocks spread out through the sky, and we can see how the ticking of the clocks changes from gravitational waves passing through our galaxy.”

Pulsars are rapidly spinning remains of massive stars that exploded as supernovas, and they send out pulses of radio waves with extreme regularity a group of them is known as a pulsar timing array, or PTA.

NANOGrav will search for gravitational wave signals with the Green Bank Telescope in West Virginia, the Very Large Array in New Mexico and the Canadian Hydrogen Intensity Mapping Experiment in Canada.

Siemens explains that using a PTA to detect a “chorus” of gravitational wave signals from multiple super-massive black hole mergers – described as a stochastic background of gravitational waves – holds more promise for understanding the universe than detecting a single wave from a single black hole binary collision.

“Each signal is like a note, and we’re not just after one of these notes – we want to hear the whole choir,” he said. “We want to hear the collective chorus of all of the super-massive black hole binaries that are merging in the universe.”

Super-massive black holes are the biggest type of black holes, millions to billions of times the mass of the sun, and they are in the centers of galaxies.

“We may already have seen the first hints of a gravitational-wave signal,” Siemens said. “This center will ensure that researchers have the resources necessary to explore one of the most exciting frontiers in all of physics and astronomy.”

Oregon State is one of 11 institutions to host an NSF Physics Frontiers Center and one of three from the Pacific 12 Conference the other two Pac-12 schools are the University of California, Berkeley, and the University of Colorado. Rounding out the list of physics frontiers sites are the University of Rochester Princeton University the University of Illinois Rice University Massachusetts Institute of Technology Caltech Michigan State and the University of Maryland.

The other centers’ research areas range from theoretical biological physics and the physics of living cells to quantum information and nuclear astrophysics.

## Big Astro News: LIGO experiment detects gravitational waves

Thursday, February 11, 2016, 12:26 PM - Today, astrophysicists from LIGO - the Laser Interferometer Gravitational-Wave Observatory - announced the first detection of gravitational waves, ripples in the fabric of spacetime caused by two massive black holes consuming each other.

Roughly a century ago, Albert Einstein changed our view of the universe when he introduced his General Theory of Relativity. Part of this was the realization that space and time were not separate parts of the universe, but were woven together into the same fabric - spacetime.

If we could actually see spacetime, it would appear as a giant sheet stretching throughout the universe, and all the matter in the universe - planets, stars, nebula, galaxies, dark matter - would be resting on top of it. Each of these objects, both separately and collectively, would press down on the sheet, causing depressions in the fabric, with more massive objects causing deeper depressions. What we experience as gravity - the force that "pulls" us towards the center of the Earth, and what keeps Earth and the other planets orbiting around the Sun - is a consequence of these depressions, which have come to be known as gravity wells.

The Sun and Earth (not to scale) causing gravity wells in the fabric of spacetime. Credit: LIGO

Along with this concept of the "fabric" of spacetime came the realization that as objects interact with spacetime, they can cause ripples in that fabric.

An excellent example of this is two massive objects orbiting closely around each other. Put a binary pair of neutron stars or black holes together, and these massive, compact, fast-moving objects would cause swirling distortions - ripples, if you will - in the fabric of spacetime as they revolved around each other.

Binary neutron stars form gravitational waves in the fabric of spacetime. Credit: NASA

These ripples, even from the largest of masses, would be extremely small. They are exaggerated in the simulation above, so that we can see them, but according to the LIGO scientists, the ripples that were detected by their laser interferometer were roughly a thousandth of the width of an atomic nucleus.

So, what happened, exactly, and what did this detection look like?

Over one billion light years away, two massive black holes - one 29 times the mass of our Sun and the other 36 times the mass of our Sun - were orbiting around each other. As the pair distorted spacetime around them, the ripples they set off spread throughout spacetime, carrying away energy, which caused the pair's orbit to slow. This locked the two into a death spiral which eventually ended with their merger, which caused an intense pulse of gravitational waves that travelled across the fabric of spacetime until they reached us here at Earth.

Although the merger happened roughly 1.3 billion years ago, those ripples arrived here at exactly 5:51 a.m. Eastern Daylight Time, on September 14, 2015, and as they swept through local spacetime, it caused the Earth to "jiggle" ever so slightly. The effect was so small that nobody on Earth would have been able to sense that anything had happened, but the detectors at the two LIGO facilities - one in Hanford, Washington, and the other in Livingston, Louisiana - picked it up. These detectors are so sensitive that they can measure the distance between our Sun and the nearest star - a span of over 40 trillion kilometres - with an accuracy down to the width of a human hair.

#### Why is this detection important?

So, what's the big deal here? Why is this announcement so important, and why has it caused so much excitement in the science community?

When Einstein first figured out that massive objects could cause these ripples in spacetime, he also concluded that they would be so tiny that there would be no way to detect them. One hundred years later, scientists have actually accomplished this, using ingenuity to overcome the limitations that Einstein had seen at the time. So, that - on its own - is a fairly exciting achievement.

More importantly, though, this detection further solidifies Einstein's theories, and it represents an advancement in our understanding of how the universe works.

Dr. Katherine J. Mack, a theoretical astrophysicist at Melbourne University, summed it up perfectly during an appearance on Australia's ABC News network:

#### Not just gravitational waves

Although the gravitational wave detection was the most important part of this announcement, one particular detail that might get lost if it was not mentioned is the discovery of this pair of binary black holes that set off the ripples that LIGO detected.

Up until now, the concept of binary black holes - two massive stellar remnants, left behind by the deaths of two immense stars - was really only in the realm of theory. Although the physics allowed for it, and even demanded their existence, astronomers still had not actually found any.

With the detection of their gravitational waves, which gave the researchers an idea of their mass, this confirms that binary pairs of black holes do actually exist.

Also, with this detection, a whole new branch of astronomy opens up. Gravitational waves carry information along with them - specifically about the events that caused them, but possibly about the spacetime they've travelled through since then. This is information that can't be obtained using any other kind of astronomy, so it gives us a whole new way of looking at the universe around us.

Watch Below: A simulation of a binary pair of black holes spiraling in to merge

## LIGO announces detection of gravitational waves from colliding neutron stars

About 130 million years ago, two incredibly heavy, dense neutron stars spiraled around each other. Their dance brought them closer to one another and made them spin faster, until they were circling more than 100 times per second. The ensuing collision sent a shockwave through the very fabric of spacetime, which traveled across the universe at the speed of light until it rippled through the Earth at 7:41 a.m. Central time on Aug. 17, 2017.

The U.S.-based Laser Interferometer Gravitational-Wave Observatory and the Virgo detector in Italy announced on Oct. 16 that all three of their detectors had picked up the ripples, or gravitational waves, from this event. Two seconds later, a satellite looking for gamma rays registered a burst from the same direction of the sky.

The event was the first time humans have directly observed two neutron stars, the collapsed cores of bigger stars, smashing into one another. Unlike the black holes that merged in LIGO’s first detection of gravitational waves two years ago—a breakthrough that earned this year’s Nobel Prize in Physics—the newly married neutron stars gave off a bright flash of light visible for days afterward. That allowed the world’s most advanced telescopes to point in that direction of the sky, including the Dark Energy Camera in Chile and the Hubble Space Telescope and Chandra X-ray Observatory in orbit above the Earth.

The result is the first measurement of a gravitational wave event in multiple mediums—optical, gamma ray and X-ray as well as gravitational waves—and scientists said the combination opens a wealth of new scientific discovery.

This includes determining the precise location of the galaxy where the event happened, which no previous LIGO detection has been able to do. They also confirmed that gravitational waves travel at approximately the speed of light, verifying a century-old Einstein prediction. And they used gravitational waves to directly calculate the rate at which the universe is expanding.

“Any one of these findings would be groundbreaking on its own merits, and here we got all the pieces together in the span of 12 hours,” said Daniel Holz, an associate professor of physics and astrophysics who led the UChicago team, which was involved in both the LIGO and Dark Energy Survey discoveries. “This is akin to seeing the lightning bolt and hearing the thunder. We have just witnessed the birth of a new field of astronomy. It’s been an unbelievable few weeks.”

### The Hubble constant: Chasing a ‘white whale’

Holz is a co-author on 12 papers published Oct. 16 on the event, including a leading role in one published in Nature announcing an entirely new measurement of the rate at which the universe is expanding.

Originally suggested by famed astronomer and UChicago alumnus Edwin Hubble, this number, called the Hubble constant, is important to such central questions in astrophysics as the age of the universe and the nature of dark matter and dark energy. It’s also at the center of a raging controversy.

Everyone agrees on the ballpark number, but whether it’s exactly 67 or 72 kilometers per second per megaparsec is hotly debated. Different methods of computing the constant spit out different results, and, Holz said, “they disagree by more than they should.”

Gravitational waves should be one of the cleanest ways to compute the number, Holz said, because scientists understand the physics of what’s happening very well. “Other ways involve many more steps and calibrations that we aren’t sure about,” he said, “but gravitational waves give you this very elegant way to perform this fundamental measurement.”

The initial calculations show LIGO’s number smack in the middle of other estimates, at 70 kilometers per second per megaparsec.

In 2006 Holz was the first to suggest the concept of calculating the Hubble constant via gravitational waves from a gamma-ray burst, calling it a “standard siren,” a nod to the term used to describe certain types of supernovas used for the same calculation called “standard candles.”

“Everyone has their white whale, and mine has been to detect the Hubble constant with gravitational waves,” he said. “And now we’ve done it. A few hours after the discovery I sat down and made the plot, and there it was, the culmination of all those years, right in front of me. And it was beautiful.”

### A literal and figurative gold mine

The neutron star merger is also the closest signal to be detected by gravitational waves, and the closest gamma-ray burst—only about 130 million light-years away, as opposed to the first black hole merger, which was more than a billion light-years away. “That’s really in our cosmological backyard,” Holz said.

Neutron stars are unfathomably dense—the weight of one-and-a-half suns packed into a ball just a dozen or so miles across. They give out a fainter gravitational wave signal than black holes, Holz said, so such proximity is necessary to capture them—even for the extraordinary sensitivity of the detectors.

Most scientists, even optimists, predicted it would be a decade before they would see a neutron star collision and be able to take such a measurement in all mediums, he said.

“This event is a gold mine—literally and figuratively,” Holz said. “We're going to learn an incredible amount about astrophysics and cosmology from studying its properties. We're also watching the production of most of the gold in the universe,” since initial studies of the event suggest that such star collisions are likely to be the origin of the heaviest elements in the universe, including gold. (Back-of-the-envelope calculations indicate that this single collision produced an amount of gold greater than the weight of the Earth, Holz said.) This solves a decades-long mystery of where about half of all elements heavier than iron are produced.

The researchers also noted the incredible good fortune of the detection’s timing. There are three gravitational wave detectors in the world: two in the U.S. run by LIGO, located in Washington and Louisiana, and one in Italy. The Italian detector had just started up, and the Louisiana and Hanford locations were just a week from shutting down for a year of maintenance. The event took place in the brief three-week window when all three gravitational wave detectors happened to be on—crucial for an accurate triangulation of the location.

Each detector has two identical arms several miles long, held at right angles to one another. Lasers run the length of each arm, perfectly calibrated to combine in tune with one another, unless one arm suddenly becomes slightly shorter or longer than the other—as would only happen if the universe itself is rippling.

Aside from analyzing all of the data they already have, Holz said, they are still measuring the radio waves produced from the ejected material interacting with the surrounding environment.

“We’ll be mining this data for a long time,” he said.

“With this we truly open a new era of astronomy,” he said. “We used to have only one way to look at the sky, but by combining existing telescopes and gravitational waves, we can learn staggeringly more about the universe.”

### UChicago, Fermilab part of collaboration

Hundreds of scientists are now sorting through the results. The UChicago LIGO team included postdoctoral fellow Ben Farr (now a professor at the University of Oregon) and graduate students Hsin-Yu Chen (now at Harvard), Zoheyr Doctor and Maya Fischbach, as well as Reed Essick, who started this fall at UChicago as a Kavli Institute for Cosmological Physics Fellow.

The UChicago team works closely with colleagues at Fermi National Acceleratory Laboratory and elsewhere on the Dark Energy Survey, which captured optical pictures of the merger just hours after LIGO and Virgo detected the gravitational waves. The scientists looked by eye at the telescope’s digital photographs for bright spots that hadn’t been there before in the section of the sky LIGO indicated, and found a new source in the galaxy labeled NGC 4993.

“Because we’re on the telescope nearly every night at that time of year, we were able to watch it peak and then fade very rapidly and could precisely map its brightness and color over time,” said Josh Frieman, UChicago professor of astronomy and astrophysics and the director of the Dark Energy Survey. “This development is very exciting for us, because more data on the expansion rate of the universe will help us chart the billion-year history of the cosmic tug-of-war between gravity and dark energy.”

Holz was on a plane from Hong Kong when the Aug. 17 gravitational wave event happened. He landed to dozens of texts and notifications. “I walked off the plane with my laptop held up to my face, and that’s basically how I’ve been walking around ever since,” he said. “Nature has given us these wonderful gifts. We’re all sleep-deprived, but no one’s complaining.”

Citation: “A gravitational-wave standard siren measurement of the Hubble constant.” Nature, Oct. 16, 2017. doi:10.1038/nature24471

Funding: LIGO is funded by theinstitutions from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration and the Australian collaboration OzGrav.

The Virgo collaboration consists of more than 280 physicists and engineers belonging to the Centre National de la Recherche Scientifique (CNRS) in France the Istituto Nazionale di Fisica Nucleare (INFN) in Italy the Netherlands’ Nikhef the MTA Wigner RCP in Hungary the POLGRAW group in Poland the University of Valencia in Spain and the European Gravitational Observatory, the laboratory hosting the Virgo detector near Pisa in Italy, which is funded by CNRS, INFN, and Nikhef.

Who's keen for the LIGO announcement?! It can be found here:

UPDATE: "We. Have. Detected gravitational waves" . Collides about 1.3bil years ago. Detected September 15, 2015. 29 and 32 solar mass blackholes merged. Both masses have an uncertainty of 4M_sun. First time a binary blackhole has been observed.

3+-0.5 solar masses lost in energy. That is 50x the energy of the observable universe.

The signal came from the southern skies!

National Science Foundation is providing a live webcast of the press conference being held in Washington D.C.

Thanks! Up vote this! I'll update the thread

"This video contains content from CondeNast, who has blocked it on copyright grounds."

I really appreciate the lady in yellow.

By the way, this whole week I've been attending a conference and we've just had talks from some of the LIGO team. The detection is much greater than 5.1 sigma. Its a bit complicated to explain how this is calculated (that used 16 days of white noise and shift of data to calculate they likelihood that this is false) but they just don't bother calculating the significance accurately if its greater than 5.1.

Looking at the plots, the standard deviation is a few thousand, so this is real.

Could someone do a quick ELI5?

In 1915 Einstein created a theory of how gravity works on large scale. He said space and time could be kind of like a blanket where if you put something on it it will dent a bit. If you try to bounce a ball on this blanket you should get waves like throwing a pebble in a pond. Unfortunately these waves are really hard to make and need something as massive as a clue of black holes so that we can see them.

The idea behind LIGO is that a gravity wave makes the shape of space get funky in some fixed direction. We can detect them by having two light beams perpendicular to each other and we time them. If a gravity wave passes in one direction we will get a slightly longer time on the laser to the detector than expected. This was proven beyond 99.99% certainty.

When you throw a rock into an undisturbed lake, it makes ripples that spread out from the point of impact. The last part of Einstein's general relativity theory needing to be discovered was that gravity warps space in the same manner. Unfortunately, because we can't "throw a rock" and look for ripples, they needed to wait until something massive happened (two black holes merging somewhere in the universe) and the ripples got to us for us to detect them.

Now try doing the rock experiment at the ocean where there are lots of big waves and lots of environmental noise. Throw a rock as far as you can and look for the ripples at the shore. It's possible, but only just. What LIGO is capable of looking for is akin to looking at Atlantic City, NJ for ripples from a pebble thrown into the English channel.

I feel someone else could explain this better, but mass bends spacetime. This is stronger with more massive objects (blackhole, neutron stars). If two big things are orbiting each other they bend space as they orbit.

Another object that encounters these waves bends and stretches, but this is so tiny, its nearly impossible to detect. The way we detect it is with lasers. (That's a little more complicated).

Anyway, the most obvious waves come from really big things! And to make gravitational waves the system needs to lost energy, so they lose energy and fall into each other. The earth and sun are radiating gravitational waves but its so measly its not significant.

All of this is a prediction of Einstein's general relativity, and for a long time is was though it wouldn't be possible to detect. But this discovery is so important because it confirms this!

## National Science Foundation - Where Discoveries Begin

Scientists representing LIGO, Virgo, and some 70 observatories will reveal new details and discoveries made in the ongoing search for gravitational waves

LIGO's detector site in Livingston, Louisiana.

October 11, 2017

This material is available primarily for archival purposes. Telephone numbers or other contact information may be out of date please see current contact information at media contacts.

WHAT:
Journalists are invited to join the National Science Foundation (NSF) as it brings together scientists from the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo collaborations, as well as representatives for some 70 observatories, Monday, Oct. 16, at 10 a.m. EDT at the National Press Club in Washington, D.C.

The gathering will begin with an overview of new findings from LIGO, Virgo and partners that span the globe, followed by details from telescopes that work with the LIGO and Virgo collaborations to study extreme events in the cosmos.

The first detection of gravitational waves, made Sept. 14, 2015 and announced Feb. 11, 2016, was a milestone in physics and astronomy it confirmed a major prediction of Albert Einstein&rsquos 1915 general theory of relativity, and marked the beginning of the new field of gravitational-wave astronomy. Since then, there have been three more confirmed detections, one of which (the most recently announced) was the first confirmed detection seen jointly by both the LIGO and Virgo detectors.

The published articles announcing LIGO&rsquos first, second, and third confirmed detections have been cited more than 1,700 times total, according to Web of Science citation counts. A fourth paper on the three-detector observation was published Oct 6 a manuscript was made publicly available Sept. 27.

Journalists interested in attending should RSVP to [email protected] as soon as possible, and by 12 p.m. EDT Friday, Oct. 13 at the latest, to guarantee a response.

WHEN:
Monday, Oct. 16, 2017
10 a.m. U.S. EDT
** Panels will begin at 10 a.m. and 11:15 a.m., with a 15-minute break in between. The event is expected to conclude by 12:30 p.m. Light refreshments will be provided.

WHERE:
The National Press Club
Holeman Lounge
529 14th St. NW, 13th Floor
Washington, DC 20045

WHO:
The following researchers will offer brief opening remarks over the course of two panels, with time for questions at the end of each panel:

Moderator: France Córdova, director of the National Science Foundation

• David Reitze, executive director, LIGO Laboratory/Caltech
• David Shoemaker, spokesperson, LIGO Scientific Collaboration/MIT
• Jo van den Brand, spokesperson, Virgo Collaboration/Nikhef, VU University Amsterdam
• Julie McEnery, Fermi Project scientist, NASA&rsquos Goddard Space Flight Center
• Marica Branchesi, Virgo Collaboration/Gran Sasso Science Institute, Italy
• Vicky Kalogera, astrophysicist, LIGO Scientific Collaboration/Northwestern University

Moderator: Jim Ulvestad, NSF acting assistant director for Mathematical and Physical Sciences

• Laura Cadonati, deputy spokesperson, LIGO Scientific Collaboration/Georgia Tech
• Andy Howell, staff scientist at Las Cumbres Observatory/UC-Santa Barbara
• Ryan Foley, assistant professor of astronomy and astrophysics, University of California-Santa Cruz
• Marcelle Soares-Santos, assistant professor, Fermi National Accelerator Laboratory/Brandeis University
• David Sand, assistant professor in astronomy, University of Arizona
• Nial Tanvir, professor of astrophysics, University of Leicester, UK
• Edo Berger, professor of astronomy, Harvard University
• Eleonora Troja, research scientist at NASA Goddard Space Flight Center/University of Maryland
• Alessandra Corsi, assistant professor, Department of Physics and Astronomy, Texas Tech University

MEDIA RSVP & INQUIRIES:

Due to seating constraints and security at the venue, journalists interested in attending should RSVP to [email protected] as soon as possible, and by 12 p.m. EDT Friday, Oct. 13, at the latest, to guarantee a response. We will try to accept RSVPs after that point, but cannot guarantee access. A mult box will be available for broadcast media, and the Press Club is equipped with wireless access.

Reporters interested in receiving embargoed information related to the research being presented can contact the media representative listed below or email [email protected] in doing so, please confirm that you and your outlet&rsquos editors honor embargoes. We will then share embargoed material with you Friday, Oct. 13.

To RSVP or request embargoed material, please email [email protected] Please refer other questions to the public information officers listed in the "Media Contacts" section below.

LIVE WEBCAST:

For press not based in the Washington, D.C., area, this event will be simulcast live online, and we will try to answer some questions submitted remotely. For details about how to participate remotely, please contact Aya Collins at NSF.

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 NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council) 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. Additional partners are listed at http://ligo.org/partners.php.

The Virgo collaboration consists of more than 280 physicists and engineers belonging to 20 different European research groups: six from Centre National de la Recherche Scientifique (CNRS) in France eight 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 the University of Valencia and the European Gravitational Observatory, EGO, the laboratory hosting the Virgo detector near Pisa in Italy, funded by CNRS, INFN, and Nikhef.

## National Science Foundation - Where Discoveries Begin

LIGO opens new window on the universe with observation of gravitational waves from colliding black holes

Aerial view of the LIGO laboratory in Louisiana.

February 11, 2016

This material is available primarily for archival purposes. Telephone numbers or other contact information may be out of date please see current contact information at media contacts.

For the first time, scientists have observed ripples in the fabric of spacetime called gravitational waves, arriving at Earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein's 1915 general theory of relativity and opens an unprecedented new window to the cosmos.

Gravitational waves carry information about their dramatic origins and about the nature of gravity that cannot be obtained from elsewhere. Physicists have concluded that the detected gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes had been predicted but never observed.

The gravitational waves were detected on Sept. 14, 2015, at 5:51 a.m. EDT (09:51 UTC) by both of the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington. The LIGO observatories are funded by the National Science Foundation (NSF) and were conceived, built and are operated by the California Institute of Technology (Caltech) and the Massachusetts Institute of Technology (MIT). The discovery, accepted for publication in the journal Physical Review Letters, was made by the LIGO Scientific Collaboration (which includes the GEO Collaboration and the Australian Consortium for Interferometric Gravitational Astronomy) and the Virgo Collaboration using data from the two LIGO detectors.

Based on the observed signals, LIGO scientists estimate that the black holes in this event were about 29 and 36 times the mass of the sun, and the event took place 1.3 billion years ago. About three times the mass of the sun was converted into gravitational waves in a fraction of a second -- with a peak power output about 50 times that of the whole visible universe. By looking at the time of arrival of the signals -- the detector in Livingston recorded the event 7 milliseconds before the detector in Hanford -- scientists can say that the source was located in the Southern Hemisphere.

According to general relativity, a pair of black holes orbiting around each other lose energy through the emission of gravitational waves, causing them to gradually approach each other over billions of years, and then much more quickly in the final minutes. During the final fraction of a second, the two black holes collide at nearly half the speed of light and form a single, more massive black hole, converting a portion of the combined black holes' mass to energy, according to Einstein's formula E=mc 2 . This energy is emitted as a final strong burst of gravitational waves. These are the gravitational waves that LIGO observed.

The existence of gravitational waves was first demonstrated in the 1970s and 1980s by Joseph Taylor Jr., and colleagues. In 1974, Taylor and Russell Hulse discovered a binary system composed of a pulsar in orbit around a neutron star. Taylor and Joel M. Weisberg in 1982 found that the orbit of the pulsar was slowly shrinking over time because of the release of energy in the form of gravitational waves. For discovering the pulsar and showing that it would make possible this particular gravitational wave measurement, Hulse and Taylor were awarded the 1993 Nobel Prize in Physics.

The new LIGO discovery is the first observation of gravitational waves themselves, made by measuring the tiny disturbances the waves make to space and time as they pass through the Earth.

"Our observation of gravitational waves accomplishes an ambitious goal set out over five decades ago to directly detect this elusive phenomenon and better understand the universe, and, fittingly, fulfills Einstein's legacy on the 100th anniversary of his general theory of relativity," says Caltech's David H. Reitze, executive director of the LIGO Laboratory.

The discovery was made possible by the enhanced capabilities of Advanced LIGO, a major upgrade that increases the sensitivity of the instruments compared to the first generation LIGO detectors, enabling a large increase in the volume of the universe probed -- and the discovery of gravitational waves during its first observation run. NSF is the lead financial supporter of Advanced LIGO. Funding organizations in Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council, STFC) and Australia (Australian Research Council) also have made significant commitments to the project.

Several of the key technologies that made Advanced LIGO so much more sensitive were developed and tested by the German UK GEO collaboration. Significant computer resources were contributed by the AEI Hannover Atlas Cluster, the LIGO Laboratory, Syracuse University and the University of Wisconsin-Milwaukee. Several universities designed, built and tested key components for Advanced LIGO: The Australian National University, the University of Adelaide, the University of Florida, Stanford University, Columbia University of the City of New York and Louisiana State University (LSU).

"In 1992, when LIGO's initial funding was approved, it represented the biggest investment NSF had ever made," says France Córdova, NSF director. "It was a big risk. But NSF is the agency that takes these kinds of risks. We support fundamental science and engineering at a point in the road to discovery where that path is anything but clear. We fund trailblazers. It's why the U.S. continues to be a global leader in advancing knowledge."

LIGO research is carried out by the LIGO Scientific Collaboration (LSC), a group of more than 1,000 scientists from universities around the United States and in 14 other countries. More than 90 universities and research institutes in the LSC develop detector technology and analyze data approximately 250 students are strong contributing members of the collaboration. The LSC detector network includes the LIGO interferometers and the GEO600 detector. The GEO team includes scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI), Leibniz Universität Hannover, along with partners at the University of Glasgow, Cardiff University, the University of Birmingham, other universities in the United Kingdom and the University of the Balearic Islands in Spain.

"This detection is the beginning of a new era: The field of gravitational wave astronomy is now a reality," says Gabriela González, LSC spokesperson and professor of physics and astronomy at Louisiana State University.

LIGO was originally proposed as a means of detecting gravitational waves in the 1980s by Rainer Weiss, professor of physics, emeritus, from MIT Kip Thorne, Caltech's Richard P. Feynman Professor of Theoretical Physics, emeritus and Ronald Drever, professor of physics, emeritus, also from Caltech.

"The description of this observation is beautifully described in the Einstein theory of general relativity formulated 100 years ago and comprises the first test of the theory in strong gravitation. It would have been wonderful to watch Einstein's face had we been able to tell him," says Weiss.

"With this discovery, we humans are embarking on a marvelous new quest: The quest to explore the warped side of the universe -- objects and phenomena that are made from warped spacetime. Colliding black holes and gravitational waves are our first beautiful examples," says Thorne.

Virgo research is carried out by the Virgo Collaboration, consisting of more than 250 physicists and engineers belonging to 19 different European research groups: six from Centre National de la Recherche Scientifique (CNRS) in France eight from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy two in the Netherlands with Nikhef the Wigner RCP in Hungary the POLGRAW group in Poland and the European Gravitational Observatory (EGO), the laboratory hosting the Virgo detector near Pisa in Italy.

Fulvio Ricci, Virgo spokesperson, notes that: "This is a significant milestone for physics, but more importantly merely the start of many new and exciting astrophysical discoveries to come with LIGO and Virgo."

Bruce Allen, managing director of the Max Planck Institute for Gravitational Physics adds: "Einstein thought gravitational waves were too weak to detect, and didn't believe in black holes. But I don't think he'd have minded being wrong!"

"The Advanced LIGO detectors are a tour de force of science and technology, made possible by a truly exceptional international team of technicians, engineers and scientists," says David Shoemaker of MIT, the project leader for Advanced LIGO. "We are very proud that we finished this NSF-funded project on time and on budget."

At each observatory, the 2 1/2-mile (4-km) long, L-shaped LIGO interferometer uses laser light split into two beams that travel back and forth down the arms (4-foot diameter tubes kept under a near-perfect vacuum). The beams are used to monitor the distance between mirrors precisely positioned at the ends of the arms. According to Einstein's theory, the distance between the mirrors will change by an infinitesimal amount when a gravitational wave passes by the detector. A change in the lengths of the arms smaller than one-ten-thousandth the diameter of a proton (10 -19 meter) can be detected.

"To make this fantastic milestone possible took a global collaboration of scientists -- laser and suspension technology developed for our GEO600 detector was used to help make Advanced LIGO the most sophisticated gravitational wave detector ever created," says Sheila Rowan, professor of physics and astronomy at the University of Glasgow.

Independent and widely separated observatories are necessary to determine the direction of the event causing the gravitational waves, and also to verify that the signals come from space and are not from some other local phenomenon.

Toward this end, the LIGO Laboratory is working closely with scientists in India at the Inter-University Centre for Astronomy and Astrophysics, the Raja Ramanna Centre for Advanced Technology, and the Institute for Plasma to establish a third Advanced LIGO detector on the Indian subcontinent. Awaiting approval by the government of India, it could be operational early in the next decade. The additional detector will greatly improve the ability of the global detector network to localize gravitational-wave sources.

"Hopefully this first observation will accelerate the construction of a global network of detectors to enable accurate source location in the era of multi-messenger astronomy," says David McClelland, professor of physics and director of the Centre for Gravitational Physics at the Australian National University.

The LIGO detector in Washington.
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A technician works on one of LIGO's optics.
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Researchers at NSF press conference announce direct observation of gravitational waves.
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Media Contacts
Ivy F. Kupec, NSF, 703-292-8796, email: [email protected]
Kimberly Allen, MIT, 617-253-2702, email: [email protected]
Kathy Svitil, Caltech, 626-676-7628, email: [email protected]
Susanne Milde, GEO600, +49 331 583 93 55, email: [email protected]
Fulvio Ricci, VIRGO Collaboration, +39 06 49914261, email: [email protected]
Terry O'Connor, UK Science and Technology Facilities Council, +44 1793 442006, email: terry.o'[email protected]

The U.S. National Science Foundation propels the nation forward by advancing fundamental research in all fields of science and engineering. NSF supports research and people by providing facilities, instruments and funding to support their ingenuity and sustain the U.S. as a global leader in research and innovation. With a fiscal year 2021 budget of \$8.5 billion, NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and institutions. Each year, NSF receives more than 40,000 competitive proposals and makes about 11,000 new awards. Those awards include support for cooperative research with industry, Arctic and Antarctic research and operations, and U.S. participation in international scientific efforts.

The LIGO detector in Washington.
Credit and Larger Version

A technician works on one of LIGO's optics.
Credit and Larger Version

Researchers at NSF press conference announce direct observation of gravitational waves.
Credit and Larger Version

## Gravity Matters

Back in 1916, while proposing the General Theory of Relativity, Einstein already predicted the existence of Gravitational Waves (GW). It took us a century to attain the technological advances to directly detect these tiny ripples in spacetime. The discovery by the LIGO-Virgo collaboration led to the Nobel prize in Physics in 2017 being awarded to Rainer Weiss, Kip Thorne and Barry Barish for this ground-breaking achievement, which opened up an entirely new window into the invisible Universe. Ever since, ever more surprising events are being observed in the Gravitational Wave sky, with the discovery of new compact objects that enrich our knowledge of extreme Physics.

As we look forward to the next generation of Gravitational Wave observatories such as the upcoming LIGO-India detector, we need now more than ever a global platform to share our current understanding of the Gravitational Wave science, to mentor and foster a skilled and informed generation of students who will be able to harness the potential of the vast pool of data rich in Science that will soon be available.