LIGO Announces Gravitational Wave Detection

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LIGO Announces Gravitational Wave Detection

Post by Eternal_Freedom » 2016-02-11 11:35am

Don't think I've seen this posted yet, so here we go. Source.

Better images/video at the source article.
The BBC wrote:Scientists are claiming a stunning discovery in their quest to fully understand gravity.

They have observed the warping of space-time generated by the collision of two black holes more than a billion light-years from Earth.

The international team says the first detection of these gravitational waves will usher in a new era for astronomy.

It is the culmination of decades of searching and could ultimately offer a window on the Big Bang.

The research, by the Ligo Collaboration, has been accepted for publication in the journal Physical Review Letters.

The collaboration operates a number of labs around the world that fire lasers through long tunnels, trying to sense ripples in the fabric of space-time.

Expected signals are extremely subtle, and disturb the machines, known as interferometers, by just fractions of the width of an atom.

But the black hole merger was picked up by two widely separated LIGO facilities in the US.

"We have detected gravitational waves," David Reitze, executive director of the Ligo project, told journalists at a news conference in Washington DC.

"It's the first time the Universe has spoken to us through gravitational waves. Up until now, we've been deaf."

Prof Karsten Danzmann, from the Max Planck Institute for Gravitational Physics and Leibniz University in Hannover, Germany, is a European leader on the collaboration.

He said the detection was one of the most important developments in science since the discovery of the Higgs particle, and on a par with the determination of the structure of DNA.

"There is a Nobel Prize in it - there is no doubt," he told the BBC.

"It is the first ever direct detection of gravitational waves; it's the first ever direct detection of black holes and it is a confirmation of General Relativity because the property of these black holes agrees exactly with what Einstein predicted almost exactly 100 years ago."

Ripples in the fabric of space-time

Gravitational waves are prediction of the Theory of General Relativity
Their existence has been inferred by science but only now directly detected
They are ripples in the fabric of space and time produced by violent events
Accelerating masses will produce waves that propagate at the speed of light
Detectable sources ought to include merging black holes and neutron stars
LIGO fires lasers into long, L-shaped tunnels; the waves disturb the light
Detecting the waves opens up the Universe to completely new investigations

That view was reinforced by Professor Stephen Hawking, who is an expert on black holes. Speaking exclusively to BBC News he said he believed that the detection marked a moment in scientific history.

"Gravitational waves provide a completely new way at looking at the Universe. The ability to detect them has the potential to revolutionise astronomy. This discovery is the first detection of a black hole binary system and the first observation of black holes merging," he said.

"Apart from testing (Albert Einstein's theory of) General Relativity, we could hope to see black holes through the history of the Universe. We may even see relics of the very early Universe during the Big Bang at some of the most extreme energies possible."

Team member Prof Gabriela González, Louisiana State University said: "We have discovered gravitational waves from the merger of black holes. It's been a very long road, but this is just the beginning.

"Now that we have the detectors to see these systems, now that we know binary black holes are out there, we'll begin listening to the Universe. "

The Ligo laser interferometers in Hanford, in Washington, and Livingstone, in Louisiana, were only recently refurbished and had just come back online when they sensed the signal from the collision. This occurred at 10.51 GMT on 14 September last year.

On a graph, the data looks like a symmetrical, wiggly line that gradually increases in height and then suddenly fades away.

"We found a beautiful signature from of the merger of two black holes and it agrees exactly - fantastically - with the numerical solutions to Einstein equations... it looked too beautiful to be true," said Prof Danzmann.

Prof Sheila Rowan, who is one of the lead UK researchers involved in the project, said that the first detection of gravitational waves was just the start of a "terrifically exciting" journey.

"The fact that we are sitting here on Earth feeling the actual fabric of the Universe stretch and compress slightly due to the merger of black holes that occurred just over a billion years ago - I think that's phenomenal. It's amazing that when we first turned on our detectors, the Universe was ready and waiting to say 'hello'," the Glasgow University scientist told the BBC.

Being able to detect gravitational waves enables astronomers finally to probe what they call "dark Universe" - the majority part of the cosmos that is invisible to the light telescopes in use today.
Perfect probe

Not only will they be able to investigate black holes and strange objects known as neutron stars (giant suns that have collapsed to the size of cities), they should also be able to "look" much deeper into the Universe - and thus farther back in time. It may even be possible eventually to sense the moment of the Big Bang.

"Gravitational waves go through everything. They are hardly affected by what they pass through, and that means that they are perfect messengers," said Prof Bernard Schutz, from Cardiff University, UK.

"The information carried on the gravitational wave is exactly the same as when the system sent it out; and that is unusual in astronomy. We can't see light from whole regions of our own galaxy because of the dust that is in the way, and we can't see the early part of the Big Bang because the Universe was opaque to light earlier than a certain time.

"With gravitational waves, we do expect eventually to see the Big Bang itself," he told the BBC.

In addition, the study of gravitational waves may ultimately help scientists in their quest to solve some of the biggest problems in physics, such as the unification of forces, linking quantum theory with gravity.

At the moment, the General Relativity describes the cosmos on the largest scales tremendously well, but it is to quantum ideas that we resort when talking about the smallest interactions. Being able to study places in the Universe where gravity is extreme, such as at black holes, may open a path to new, more complete thinking on these issues.

A laser is fed into the machine and its beam is split along two paths
The separate paths bounce back and forth between damped mirrors
Eventually, the two light parts are recombined and sent to a detector
Gravitational waves passing through the lab should disturb the set-up
Theory holds they should very subtly stretch and squeeze its space
This ought to show itself as a change in the lengths of the light arms (green)
The photodetector captures this signal in the recombined beam

Scientists have sought experimental evidence for gravitational waves for more than 40 years.

Einstein himself actually thought a detection might be beyond the reach of technology.

His theory of General Relativity suggests that objects such as stars and planets can warp space around them - in the same way that a billiard ball creates a dip when placed on a thin, stretched, rubber sheet.

Gravity is a consequence of that distortion - objects will be attracted to the warped space in the same way that a pea will fall in to the dip created by the billiard ball.
Inspirational moment

Einstein predicted that if the gravity in an area was changed suddenly - by an exploding star, say - waves of gravitational energy would ripple across the Universe at light-speed, stretching and squeezing space as they travelled.

Although a fantastically small effect, modern technology has now risen to the challenge.

Much of the R&D work for the Washington and Louisiana machines was done at Europe's smaller GEO600 interferometer in Hannover.

"I think it's phenomenal to be able to build an instrument capable of measuring [gravitational waves]," said Prof Rowan.

"It is hugely exciting for a whole generation of young people coming along, because these kinds of observations and this real pushing back of the frontiers is really what inspires a lot of young people to get into science and engineering."
Baltar: "I don't want to miss a moment of the last Battlestar's destruction!"
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Baltar: "What are you babbling about other...it's impossible!"
Centurion: "No. It is a Battlestar."

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Scientists have detected gravity waves for the first time

Post by Borgholio » 2016-02-11 11:47am

http://www.nasa.gov/feature/goddard/201 ... onal-waves
The National Science Foundation (NSF) has announced the detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO), a pair of ground-based observatories in Hanford, Washington, and Livingston, Louisiana.

Albert Einstein predicted the existence of gravitational waves in his general theory of relativity a century ago, and scientists have been attempting to detect them for 50 years. Einstein pictured these waves as ripples in the fabric of space-time produced by massive, accelerating bodies, such as black holes orbiting each other. Scientists are interested in observing and characterizing these waves to learn more about the sources producing them and about gravity itself.

The LIGO detections represent a much-awaited first step toward opening a whole new branch of astrophysics. Nearly everything we know about the universe comes from detecting and analyzing light in all its forms across the electromagnetic spectrum – radio, infrared, visible, ultraviolet, X-rays and gamma rays. The study of gravitational waves opens a new window on the universe, one that scientists expect will provide key information that will complement what we can learn through electromagnetic radiation.

Just as in other areas of astronomy, astronomers need both ground-based and space-based observatories to take full advantage of this new window. LIGO is sensitive to gravitational waves within the range of 10 to 1,000 cycles per second (10 to 1,000 Hz). A space-based system would be able to detect waves at much lower frequencies, from 0.0001 to 0.1 Hz, and detect different types of sources. NASA is working closely with the European Space Agency (ESA) to develop a concept for a space-based gravitational wave observatory.

ESA is currently leading the LISA Pathfinder mission, launched last December and now in its commissioning phase, to demonstrate technologies that could be used for a future space-based gravitational wave observatory. NASA contributed its ST-7 Disturbance Reduction System to the payload as part of that demonstration.

NASA missions are searching the sky for fleeting X-ray and gamma-ray signals from LIGO events. Detecting the light emitted by a gravitational wave source would enable a much deeper understanding of the event than through either technique alone.

For more information, please visit:

https://www.ligo.caltech.edu/news/ligo20160211
http://www.nsf.gov/news/news_summ.jsp?cntn_id=137628
I am proud to say that have been donating a part of my computer's processing power to Einstein@home which was helping to search for these waves. This is very cool news!
Last edited by SCRawl on 2016-02-11 01:13pm, edited 1 time in total.
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Re: LIGO Announces Gravitational Wave Detection

Post by Sea Skimmer » 2016-02-11 05:22pm

It really goes to show just how much difference technology makes for this level of science... the original LIGO sensors operated for nearly a decade without success. The improved version started up in September 2015... and detected these gravity waves several days before it was even formally fully operational!
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Re: LIGO Announces Gravitational Wave Detection

Post by phongn » 2016-02-13 02:12am

Sea Skimmer wrote:It really goes to show just how much difference technology makes for this level of science... the original LIGO sensors operated for nearly a decade without success. The improved version started up in September 2015... and detected these gravity waves several days before it was even formally fully operational!
They didn't really expect to detect anything with Initial and Enhanced LIGO (the pre-2010 configurations). They had faint hope - and it turns out they were basically on the cusp of sensitivity with eLIGO!
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Re: LIGO Announces Gravitational Wave Detection

Post by Simon_Jester » 2016-02-13 09:45am

[This is not a refutation of anything above]

Yeah, but you have to get your equipment physically up and running before you can make sure it actually works as intended and figure out how to effectively refine its sensitivity.
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Re: LIGO Announces Gravitational Wave Detection

Post by cosmicalstorm » 2016-02-13 09:50am

Nice news. Gravitational wave observations always makes me think of Diaspora by Greg Egan.
http://www.amazon.com/Diaspora-A-Novel- ... 1597805424

Now I'm waiting for a quantum telescope.

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Re: LIGO Announces Gravitational Wave Detection

Post by jwl » 2016-02-13 11:55am

I've never heard of a quantum telescope, what does it do?

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Re: LIGO Announces Gravitational Wave Detection

Post by LaCroix » 2016-02-13 02:02pm

Ok, they exist.

Now go forth and find out how to create them, so we could enhance or cancel out local gravity by wave interference.
A minute's thought suggests that the very idea of this is stupid. A more detailed examination raises the possibility that it might be an answer to the question "how could the Germans win the war after the US gets involved?" - Captain Seafort, in a thread proposing a 1942 'D-Day' in Quiberon Bay

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Re: LIGO Announces Gravitational Wave Detection

Post by cosmicalstorm » 2016-02-13 03:15pm

jwl wrote:I've never heard of a quantum telescope, what does it do?

8)

Sci fi observatories explored in Blind Lake.
Tl dr quantum computers accidentally find a way to look very far while working to save a orbital observatory that is loosing it's radio signal to earth using neural networks and fourier transform analysis. One of the best sci-fi books I ever read.
http://www.goodreads.com/book/show/116412.Blind_Lake

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Re: LIGO Announces Gravitational Wave Detection

Post by jwl » 2016-02-13 06:45pm

cosmicalstorm wrote:
jwl wrote:I've never heard of a quantum telescope, what does it do?

8)

Sci fi observatories explored in Blind Lake.
Tl dr quantum computers accidentally find a way to look very far while working to save a orbital observatory that is loosing it's radio signal to earth using neural networks and fourier transform analysis. One of the best sci-fi books I ever read.
http://www.goodreads.com/book/show/116412.Blind_Lake
So is this just a normal radio telescope with a really good image processing algorithms?

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Gravity Wave Black Hole Merger Might Coincide With Gamma Ray Burst

Post by jwl » 2016-02-15 09:07am

On September 14, 2015 at 09:50:45 UTC advanced LIGO observed GW150914, a chirp of gravitational waves caused by the merging of two stellar-mass black holes. Just 0.4 seconds later, the Fermi gamma ray telescope observed a faint burst of gamma rays lasting about a second. While there is a small chance this is simply due to chance, it looks like the gamma ray burst was triggered by the merging black holes.

A gamma ray burst (GRB) is a transient emission of gamma rays typically lasting less than two seconds. On average, about one gamma ray burst occurs every day. They appear randomly in all directions of the sky, and this means they aren’t produced in our galaxy. If they were, then GRBs would mostly be found along the plane of the Milky Way. They are thought to be caused by things like colliding neutron stars, or possibly the capture of a neutron star by a black hole.

This particular GRB (named GW150914-GBM) was observed by the Fermi Gamma-ray Burst Monitor, which can observe 70% of the sky at any given time. That’s great for observing these short-lived events, but it means that locating the source of a particular event is a bit imprecise. The most likely location of GW150914-GBM falls within the likely location of the gravity wave source GW150914. There are other aspects of the GRB that would tend to support a simultaneous event. While the burst was faint it had a hard x-ray spectrum, which would seem to rule out known sources within our own galaxy. There is still a possibility that some extragalactic event such as the collision of neutron stars just happened to occur in the same general direction 0.4 seconds after the gravitational wave event, but that doesn’t seem likely. Given its faintness there’s also a small chance that this could be a false-alarm.

If we assume the two events have the same cause that would mean the burst also occurred 1.3 billion light years away. From its apparent peak brightness we can calculate its peak luminosity. It turns out the peak luminosity of this event is an order of magnitude dimmer than any previous short GRB event. This would support the idea that it was not caused by a neutron star collision.

If this GRB was caused by merging black holes, it would be quite surprising. Stellar mass black hole binaries aren’t expected to have a disk of material around them that could emit gamma rays. We’ll need more data to be sure. Fortunately there will be plenty of opportunity to observe similar events over the next few years.
http://www.forbes.com/sites/briankoberl ... ray-burst/
Paper:
With an instantaneous view of 70% of the sky, the Fermi Gamma-ray Burst Monitor (GBM) is an excellent partner in the search for electromagnetic counterparts to gravitational wave (GW) events. GBM observations at the time of the Laser Interferometer Gravitational-wave Observatory (LIGO)event GW150914 reveal the presence of a weak transient source above 50 keV, 0.4~s after the GW event was detected, with a false alarm probability of 0.0022. This weak transient lasting 1 s does not appear connected with other previously known astrophysical, solar, terrestrial, or magnetospheric activity. Its localization is ill-constrained but consistent with the direction of GW150914. The duration and spectrum of the transient event suggest it is a weak short Gamma-Ray Burst arriving at a large angle to the direction in which Fermi was pointing, where the GBM detector response is not optimal. If the GBM transient is associated with GW150914, this electromagnetic signal from a stellar mass black hole binary merger is unexpected. From our measurement of the fluence seen by GBM, we calculate a luminosity in hard X-ray emission between 1~keV and 10~MeV of 1.8+1.5−1.0×1049 erg s−1. The observation by Fermi GBM encompasses 75% of the probability map associated with the LIGO GW event localization at the time the GW event was detected. Assuming the two events have a common origin, the combined LIGO and GBM observations can reduce the 90% confidence interval on sky location from 601 to 199 square degrees. Future joint observations of GW events by LIGO/Virgo and Fermi GBM could reveal whether the weak transient reported here is a plausible counterpart to the GW event GW150914 or a chance coincidence, and will further probe the connection between compact binary mergers and short Gamma-Ray Bursts.
http://arxiv.org/abs/1602.03920

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LIGO Does It Again: A Second Robust Binary Black Hole Coalescence Observed

Post by jwl » 2016-06-19 06:21pm

The two LIGO gravitational wave detectors in Hanford Washington and Livingston Louisiana have caught a second robust signal from two black holes in their final orbits and then their coalescence into a single black hole. This event, dubbed GW151226, was seen on December 26th at 03:38:53 (in Universal Coordinated Time, also known as Greenwich Mean Time), near the end of LIGO's first observing period ("O1"), and was immediately nicknamed "the Boxing Day event".

Like LIGO's first detection, this event was identified within minutes of the gravitational wave's passing. Subsequent careful studies of the instruments and environments around the observatories showed that the signal seen in the two detectors was truly from distant black holes – some 1.4 billion light years away, coincidentally at about the same distance as the first signal ever detected. The Boxing Day event differed from the LIGO's first gravitational wave observation in some important ways, however.

The gravitational wave arrived at the two detectors at almost the same time, indicating that the source was located somewhere in a ring of sky about midway between the two detectors. Knowing our detector sensitivity pattern, we can add that it was a bit more likely overhead or underfoot instead of to the West or the East. With only two detectors, however, we can't narrow it down much more than that. This differs from LIGO's first detected signal (GW150914, from 14 September 2015), which came from the 'southeast', hitting Louisiana's detector before Washington's.
The two merging black holes in the Boxing Day event were less massive (14 and 8 times the mass of our sun) than those observed in the first detection GW150914 (36 and 29 times the mass of our sun). While this made the signal weaker than GW150914, when these lighter black holes merged, their signal shifted into higher frequencies bringing it into LIGO’s sensitive band earlier in the merger than we observed in the September event. This allowed us to observe more orbits than the first detection–some 27 orbits over about one second (this compares with just two tenths of a second of observation in the first detection). Combined, these two factors (smaller masses and more observed orbits) were the keys to enabling LIGO to detect a weaker signal. They also allowed us to make more precise comparisons with General Relativity. Spoiler: the signal agrees, again, perfectly with Einstein’s theory.
Last but not least, the Boxing Day event revealed that one of the initial black holes was spinning like a top! – and this is a first for LIGO to be able to state this with confidence. A spinning black hole suggests that this object has a different history –- e.g. maybe it 'sucked in' mass from a companion star before or after collapsing from a star to form a black hole, getting spun-up in the process.
With these two confirmed detections, along with a third likely detection made in October 2015 (believed also to be caused by a pair of merging black holes--see our paper draft on Black Hole Binaries in O1 for more information) we can now start to estimate the rate of black hole coalescences in the Universe based not on theory, but on real observations. Of course with just a few signals, our estimate has big uncertainties, but our best right now is somewhere between 9 and 240 binary black hole coalescences per cubic Gigaparsec per year, or about one every 10 years in a volume a trillion times the volume of the Milky Way galaxy! Happily, in its first few months of operation, LIGO’s advanced detectors were sensitive enough to probe deeply enough into space to see about one event every two months.

Our next observing interval – Observing Run #2, or "O2" – will start in the Fall of 2016. With improved sensitivity, we expect to see more black hole coalescences, and possibly detect gravitational waves from other sources, like binary neutron-star mergers. We are also looking forward to the Virgo detector joining us later in the O2 run. Virgo will be enormously helpful in locating sources on the sky, collapsing that ring down to a patch, but also helping us understand the sources of gravitational waves.

LIGO releases its data to the public. This open-data policy allows others to analyze our data, thus ensuring that the LIGO and Virgo collaborations did not miss anything in their analyses, and in the hopes that others will find even more interesting events. Our data are shared at the LIGO Open Science Center. GW151226 has its own page there.

We encourage you to wander around the LIGO Laboratory web page where you will find graphics to help you understand the Boxing Day observation, links to the press release, and pointers to scientific papers if you would like to dig in even deeper. There you will also find links to the LIGO Scientific Collaboration website, and to our sister collaboration, Virgo, both of which are central to these scientific results.
https://www.ligo.caltech.edu/news/ligo20160615

Paper:
ABSTRACT
We report the observation of a gravitational-wave signal produced by the coalescence of two stellar-mass black holes. The signal, GW151226, was observed by the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) on December 26, 2015 at 03:38:53 UTC. The signal was initially identified within 70 s by an online matched-filter search targeting binary coalescences. Subsequent off-line analyses recovered GW151226 with a network signal-to-noise ratio of 13 and a significance greater than 5σ. The signal persisted in the LIGO frequency band for approximately 1 s, increasing in frequency and amplitude over about 55 cycles from 35 to 450 Hz, and reached a peak gravitational strain of 3.4+0.7−0.9×10−22. The inferred source-frame initial black hole masses are 14.2+8.3−3.7M⊙ and 7.5+2.3−2.3M⊙, and the final black hole mass is 20.8+6.1−1.7M⊙. We find that at least one of the component black holes has spin greater than 0.2. This source is located at a luminosity distance of 440+180−190  Mpc corresponding to a redshift of 0.09+0.03−0.04. All uncertainties define a 90% credible interval. This second gravitational-wave observation provides improved constraints on stellar populations and on deviations from general relativity.
http://journals.aps.org/prl/abstract/10 ... 116.241103

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