Gravitational Waves

Reverse engineering a binary black hole merger. As predicted!

Gravitational WavesThe recent LIGO announcement of the first direct observation of Einstein’s Gravity Waves as the result of the first direct observation of a binary black hole system merging is amazing news for science and Albert Einstein’s General Theory of Relativity. The 2 black holes merging seem to have been reversed engineered and not actually observed directly? More like directly implied, as with most dark stuff in the univese.

Scientists detected gravitational waves produced by the merger of two black holes, an event so intense that in the moment before the colliding black holes swallowed each other, they emitted more energy than the rest of the universe combined.
Found! Gravitational Waves, or a Wrinkle in Spacetime | National Geographic

gravitational waves

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.

… 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 3 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.

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 into each other at nearly one-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. It is these gravitational waves that LIGO has observed.
Gravitational Waves Detected 100 Years After Einstein’s Prediction | LIGO

gravitational waves

Using a handful of Einstein’s equations, scientists backtracked from the observable waves to determine what kind of astrophysical event was to blame. In this case, those equations suggested that two colliding black holes were the culprit—and that when they coalesced, they formed a new black hole, one with a little more than 60 solar masses.
Found! Gravitational Waves, or a Wrinkle in Spacetime | National Geographic

About 1.3 billion years ago two black holes swirled closer and closer together until they crashed in a furious bang. Each black hole packed roughly 30 times the mass of our sun into a minute volume, and their head-on impact came as the two were approaching the speed of light. The staggering strength of the merger gave rise to a new black hole and created a gravitational field so strong that it distorted spacetime in waves that spread throughout space with a power about 50 times stronger than that of all the shining stars and galaxies in the observable universe.
Gravitational Waves Discovered from Colliding Black Holes | Scientific American

Gravitational Waves

“The stretching and squeezing of space is insanely small,” Weinstein says, noting that a passing gravitational wave might change the distance between two people sitting a meter apart by just 10-21 meters. That’s on the order of a millionth of the diameter of a proton, one of the particles that make up an atom’s nucleus. But put two mirrors four kilometers apart, as LIGO has done, and the effect of that gravitational wave is on the order of a ten-thousandth of the diameter of a proton. “That, we can do,” Weinstein says.

LIGO uses two identical L-shaped detectors set a continent apart, in Livingston, Louisiana, and Hanford, Washington. For a gravitational wave signal to be counted as real, it must show up in both detectors, which are made of two sets of mirrors set perpendicularly to one another. A passing gravitational wave will stretch spacetime in one direction and compress it in another, causing an inconceivably small change in the length of the detectors’ arms, which is measured by a laser.

The apparatus is the most sensitive measuring device on the planet, and in addition to gravitational waves, can detect vibrations from passing trucks, earthquakes, lightning strikes six states away, signals from global positioning satellites, and electromagnetic pulses in Earth’s upper atmosphere. All that noise has to be filtered out to pick up the minuscule signal from gravitational waves.
Found! Gravitational Waves, or a Wrinkle in Spacetime | National Geographic

The violent birth of a black hole generates a pulse of gravitational waves. But an even stronger pulse comes if two holes subsequently coalesce. This is a rare event, happening less than once in a million years in our Galaxy. But such an event would give a LIGO signal even if it happened a billion light-years away – and there are millions of galaxies closer than that.

Holes that find themselves in orbit around each other (perhaps because they are the remnant of a binary star) would gradually spiral together. As they get closer, the space around them gets more distorted and their orbital speed exceeds half the speed of light. They finally coalesce into a single, spinning, hole, which sloshes and vibrates, emitting further gravitational waves until it settles down as a single quiescent hole.

It is this “chirp” – a shaking of space that speeds up and strengthens until the merger, and then dies away – that LIGO can detect. It’s possible to calculate the wave-form of this “chirp”: it depends on how heavy the merging holes are, and how they are spinning, and how their orbit is oriented relative to the line of sight.

So data of sufficiently high quality can reveal details of what caused the events.
Gravitational waves: Einstein was right | Telegraph

Markarian 231, a binary black hole 1.3 billion light years from Earth. Their collision generated the first gravitational waves we’ve ever detected … Predicted over 100 years ago by Albert Einstein, gravitational waves are ripples in space-time. They travel in waves, like light does, but they aren’t radiation. They are actual perturbations in the fabric of space-time itself. The ones detected by LIGO, after over ten years of “listening”, came from a binary system of black holes over 1.3 billion light years away, called Markarian 231
Gravitational Waves Discovered: A New Window on the Universe | Universe Today

We have reported the properties of GW150914 derived from a coherent analysis of data from the two LIGO detectors, based on the most accurate modelling of the coalescence signal as predicted by general relativity. We have shown that GW150914 originates from a BBH system … The final BH is more massive than any other found in the stellar-mass range.
Properties of the binary black hole merger GW150914 (Link to PDF)

Gravitational Waves

The waves given off by the cataclysmic merger of GW150914 reached Earth as a ripple in spacetime that changed the length of a 4-km LIGO arm by a ten thousandth of the width of a proton, proportionally equivalent to changing the distance to the nearest star by one hair’s width.[5] The energy released during the brief climax of the event was immense, with about three solar masses converted to gravitational waves and radiated away at a peak rate of about 3.6×1049 watts – more than the combined power of all light radiated by all the stars in the observable universe.
First observation of gravitational waves | Wikipedia

The phenomenon detected was the collision of two black holes. Using the world’s most sophisticated detector, the scientists listened for 20 thousandths of a second as the two giant black holes, one 35 times the mass of the sun, the other slightly smaller, circled around each other.

At the beginning of the signal, their calculations told them how stars perish: the two objects had begun by circling each other 30 times a second. By the end of the 20 millisecond snatch of data, the two had accelerated to 250 times a second before the final collision and a dark, violent merger.
Gravitational waves: breakthrough discovery after a century of expectation | The Guardian

A billion years ago, two very large deep holes, each with the mass of about 30 suns, were orbiting each other faster and faster till they collided. From that violent merger, a wobble of energy moved through deep space and landed on Earth in September in the US.
Gravitational Waves – The Impact On You, Me And The World | NDTV

Our estimated pre-merger masses of the two components in GW150914 make a very strong argument that they are both black holes – particularly when we also consider the enormous velocity and tiny separation of the two components, as shown in the lower part of figure 3. In this figure indicative velocities of the two components are seen to be significant fractions of the speed of light. Similarly their approximate separation is shown to be just a few times the characteristic size of a black hole, known as its Schwarzschild radius.

These graphs imply that the two components were only a few hundred kilometers apart just before they merged, ie. when the gravitational-wave frequency was about 150 Hz. Black holes are the only known objects compact enough to get this close together without merging. Based on our estimated total mass for the two components, a pair of neutron stars would not be massive enough, and a black hole-neutron star pair would have already merged at a lower frequency than 150 Hz.
How do we know GW150914 was a black hole merger? – Observation of Gravitational Waves from a binary black hole merger | LIGO

“It was waving hello,” he said. “It was amazing. The signal was so big, I didn’t believe it.” The frequency of the chirp was too low for neutron stars, the physicists knew. Detailed analysis of its form told a tale of Brobdingnagian activities in a far corner of the universe: the last waltz of a pair of black holes shockingly larger than astrophysicists had been expecting.

The signal conformed precisely to the predictions of general relativity for black holes as calculated in computer simulations, Dr. Reitze said.
Gravitational Waves Detected, Confirming Einstein’s Theory | The New York Times

The LIGO/Virgo trigger reconstruction favors a binary black hole scenario.
INTEGRAL upper limits on gamma-ray emission associated with the gravitational wave event GW150914 (direct link to PDF)