Tag Archives: LIGO

Another LIGO black hole merger detected

Astronomers have announced another black hole merger detected by the LIGO gravitational wave observatory.

Dubbed GW170608, the latest discovery was produced by the merger of two relatively light black holes, 7 and 12 times the mass of the sun, at a distance of about a billion light-years from Earth. The merger left behind a final black hole 18 times the mass of the sun, meaning that energy equivalent to about 1 solar mass was emitted as gravitational waves during the collision.

This event, detected by the two NSF-supported LIGO detectors at 02:01:16 UTC on June 8, 2017 (or 10:01:16 pm on June 7 in US Eastern Daylight time), was actually the second binary black hole merger observed during LIGO’s second observation run since being upgraded in a program called Advanced LIGO. But its announcement was delayed due to the time required to understand two other discoveries: a LIGO-Virgo three-detector observation of gravitational waves from another binary black hole merger (GW170814) on August 14, and the first-ever detection of a binary neutron star merger (GW170817) in light and gravitational waves on August 17.

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Astronomers detect neutron star merger in both light and gravitational waves

Big news! Astronomers from dozens of telescopes on the ground and in space have observed for the first time the light burst caused by the merger of two neutron stars because earlier observations of the merger’s gravitational wave and gamma ray burst told them where to look in the sky.

On 17 August 2017 the NSF’s Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States, working with the Virgo Interferometer in Italy, detected gravitational waves passing the Earth. This event, the fifth ever detected, was named GW170817. About two seconds later, two space observatories, NASA’s Fermi Gamma-ray Space Telescope and ESA’s INTErnational Gamma Ray Astrophysics Laboratory (INTEGRAL), detected a short gamma-ray burst from the same area of the sky.

The LIGO–Virgo observatory network positioned the source within a large region of the southern sky, the size of several hundred full Moons and containing millions of stars. As night fell in Chile many telescopes peered at this patch of sky, searching for new sources. These included ESO’s Visible and Infrared Survey Telescope for Astronomy (VISTA) and VLT Survey Telescope (VST) at the Paranal Observatory, the Italian Rapid Eye Mount (REM) telescope at ESO’s La Silla Observatory, the LCO 0.4-meter telescope at Las Cumbres Observatory, and the American DECam at Cerro Tololo Inter-American Observatory. The Swope 1-metre telescope was the first to announce a new point of light. It appeared very close to NGC 4993, a lenticular galaxy in the constellation of Hydra, and VISTA observations pinpointed this source at infrared wavelengths almost at the same time. As night marched west across the globe, the Hawaiian island telescopes Pan-STARRS and Subaru also picked it up and watched it evolve rapidly.

Press releases today from numerous other observatories are too numerous to link here, and most essentially say the same thing. The key facts so far gleaned however are intriguing:

Distance estimates from both the gravitational wave data and other observations agree that GW170817 was at the same distance as NGC 4993, about 130 million light-years from Earth. This makes the source both the closest gravitational wave event detected so far and also one of the closest gamma-ray burst sources ever seen

This event also highlights the advantages of observing the universe in as many ways as possible. Some phenomenon get to us sooner, and thus provide us clues on where to look with other tools. Without the gravitational wave and gamma ray burst detectors, on Earth and in space, the other optical and infrared telescopes would have almost certainly not have recorded this merger.

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Nobel Prize for Physics awarded to three LIGO scientists

The 2017 Nobel Prize for Physics has been awarded to three scientists involved in the development of the Laser Interferometer Gravitational-wave Observatory (LIGO), which detected the first gravitational waves in 2015.

While some of the recent Nobel Prizes have been absurd (such as the Peace award to Obama), this award is absolutely deserved and appropriate. Until LIGO detected that gravitational wave they were merely a theory. The detection proved the theory to be real.

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Gravitational waves from black hole collision detected

Three Earth gravitational wave observatories have detected the waves coming from the same collision of two black holes.

The collision was observed Aug. 14 at 10:30:43 a.m. Coordinated Universal Time (UTC) using the two National Science Foundation (NSF)-funded Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors located in Livingston, Louisiana, and Hanford, Washington, and the Virgo detector, funded by CNRS and INFN and located near Pisa, Italy.

The detection by the LIGO Scientific Collaboration (LSC) and the Virgo collaboration is the first confirmed gravitational wave signal recorded by the Virgo detector.

Based on the data obtained, they estimate that the two black holes 25 and 31 times the mass of the Sun and are about 1.8 billion light years away.

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LIGO detects its third gravitational wave

LIGO scientists today revealed that the detector had spotted its third gravitational wave in January.

Researchers estimate that the bodies in the latest collision were slightly lighter than those in the first event: one had the mass of 31 Suns and the other 19. (The black holes in the second discovery were even more lightweight, at 14 and 8 solar masses.) But the latest merger is the most distant detected so far. The gravitational waves it produced took somewhere between 1.6 billion and 4.3 billion years to reach Earth — most probably around 2.8 billion years.

This new field of astronomy should get even more interesting in the next year or two, as new detectors come on line in Italy and Japan.

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Another gravity wave detected by LIGO

The LIGO gravitational wave detector has detected its second gravitational wave, thought to come from the merger of two black holes.

The new observation came at 3:38.53 Coordinated Universal Time on 26 December 2015—late on Christmas day at LIGO’s detectors in Livingston, Louisiana, and Hanford, Washington. As in the first event, the detectors sensed an oscillating stretching of space-time, the signal, according to Einstein’s 
general theory of relativity, of massive objects in violent motion. Computer modeling indicated that its source was two black holes spiraling together about 1.4 billion light-years away. (LIGO researchers had seen a weaker signal on 12 October 2015 that may be a third black hole merger.)

Note the last sentence in the quote above. They might have had a third detection, but are uncertain enough to have not claimed it as one.

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India signs deal for its own LIGO

India today signed an agreement with the National Science Foundation to build its own LIGO gravitational wave detector

This deal, combined with the possibility that TMT might move to India as well, suggests that India is about to move aggressively from the Third World to the First. And the reason, after decades of wallowing in poverty and failure, is that they finally abandoned in the late 1990s the Soviet models of socialism and communism and embraced private enterprise and capitalism, ideas championed by the United States.

If only some modern Americans would do the same.

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Want to discover gravitational waves? You can!

The citizen science project, Einstein@home, will begin providing its participants data from the upgraded LIGO gravitational wave detector beginning March 9.

Rather than looking for dramatic sources of gravitational waves, such as the black-hole merger that LIGO detected on 14 September, Einstein@home looks for quieter, slow-burn signals that might be emitted by fast-spinning objects such as some neutron stars. These remnants of supernova explosions are some of the least well understood objects in astrophysics: such searches could help to reveal their nature.

Because they produce a weaker signal than mergers, rotating sources require more computational power to detect. This makes them well-suited to a distributed search. “Einstein@home is used for the deepest searches, the ones that are computationally most demanding,” Papa says. The hope is to extract the weak signals from the background noise by observing for long stretches of time. “The beauty of a continuous signal is that the signal is always there,” she says.

To participate all you have to do is let their software become your screensaver, doing its work whenever you walk away from your computer.

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India okays its own LIGO detector

The Indian government today approved construction of LIGO-India, using some duplicate components already available from the American LIGO gravitational wave detector.

“We have built an exact copy of that instrument that can be used in the LIGO-India Observatory,” says David Shoemaker, leader of the Advanced LIGO Project and director of the MIT LIGO Lab, “ensuring that the new detector can both quickly come up to speed and match the U.S. detector performance.” LIGO will provide Indian researchers with the components and training to build and run the new Advanced LIGO detector, which will then be operated by the Indian team.

What this new instrument will accomplish is to give astronomers more information when a gravitational wave rolls past the Earth. By having detectors half a world apart, they will be able to better triangulate the direction the wave came from, which in turn will help astronomers eventually pinpoint its source event.

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First direct detection of a gravitational wave

The science team from the Laser Interferometer Gravitational-wave Observatory (LIGO) announced today that on September 14, 2015 they made the first direct detection of a gravitational wave, produced by the merging of two distant black holes.

Based on the observed signals, LIGO scientists estimate that the black holes for 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=mc2. This energy is emitted as a final strong burst of gravitational waves. These are the gravitational waves that LIGO observed.

Because of the faintness of the wave signal, I suspect that the scientists involved have spent the last four months reviewing their data and the instrument very carefully, to make sure this was not a false detection. That they feel confident enough to make this announcement tells us that they think the detection was real.

Recently ESA launched Lisa Pathfinder, a prototype space-based gravitational wave detector designed to test the technology for building a larger in-space observatory that would be far more sensitive that LIGO. Funding for that larger detector has dried up, Today’s announcement will likely help re-energize that funding effort.

More information here.

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The elusive effort to detect gravitational waves.

After spending more than half a billion dollars and eight years of looking without a single detection, the Laser Interferometer Gravitational-Wave Observatory (LIGO) has gotten a major upgrade.

If commissioning continues to go relatively smoothly, plans call for the first Advanced LIGO observing run to start in late 2015. A second run, with a decent shot of finding a gravitational wave, would occur in the winter of 2016–17. (Weiss likes to point out that a 2016 discovery would be a nice 100th-anniversary commemoration of Einstein’s paper describing gravitational waves.) By the third science run, planned for 2017–18, the machine should be getting sensitive enough to almost certainly nail a detection, says Reitze.

It is hoped that the increased sensitivity, ten times better than before. will allow LIGO to finally make the first detection of a gravitational wave.

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