Gravitational Waves - The first 6 detections

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On September 14th, 2015, twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) made history by capturing the first direct observation of gravitational waves. According to Einstein's groundbreaking theory of general relativity, massive objects accelerated through space and time emit ripples in spacetime that travel at the speed of light. These cosmic tremors are strong enough to be detected when massive objects, like black holes and neutron stars, collide at extremely high speeds. The merger of two black holes and a neutron star provides the perfect conditions for the emission of powerful gravitational waves. The source of the first detected signal, named GW150914, was the collision and merger of two black holes in a distant galaxy, approximately 440 megaparsecs away from Earth. These massive black holes weighed around 35 and 30 times that of our sun, resulting in a merged black hole with a mass of only 62 solar masses. The remaining energy, equivalent to three solar masses, was released as gravitational waves. Gravitational waves are dynamic distortions of spacetime itself. As they pass through objects not rigidly connected, like a floating ring of masses or the suspended test masses in LIGO detectors, they alter the distance between them. Imagine a ring of freely floating masses around Earth. When a gravitational wave passes through it distorts the ring, stretching it in one direction and compressing it in another. This distortion rotates at the same frequency as the black holes that created the gravitational wave orbited each other. As the black holes draw closer together, their orbital frequency increases, causing the gravitational waves and the distortion of our ring of masses to grow stronger. The models depicted here illustrate the time evolution of this distortion during the final one-tenth of a second before the black holes merge. Each horizontal slice represents an instant in time, with the distortion calculated for rings at Earth's location and exaggerated by a factor of 5 times 10^20. In reality, this effect is minuscule, altering the length of the 4-kilometer LIGO detectors by less than the diameter of a proton. There are six models, one for each gravitational wave signal detected to date. The first image above shows the sources of each signal, with the size of the circles corresponding to the mass and size of the objects involved. The first five signals come from black hole collisions, while the last signal, GW170817, was the merger of two neutron stars that likely formed a black hole. The amplitude of the signal depends on both the masses of the black holes, their distance from Earth, and their orientation. The frequency of the signal is determined by the mass of the black holes, with GW150914 being the heaviest and GW170608 the lightest.