14 September 2015, just a few days after the first activation, LIGO, earth passed through a gravitational wave. Like the billions of such waves, which passed through the Earth throughout its history, this was generated by the twisting, merging and collision of two massive sverhdorogih objects far beyond our galaxy. From a distance of more than a billion light-years we received a signal about the merger of two black holes. Signal, moving at the speed of light finally reached Earth.
This time we were ready. Dual detectors LIGO saw their sleeves expanded and shrunk to subatomic size, but it was enough to make the laser beam shifted and made the obvious change of the interference picture. For the first time, we detected a gravity wave. Three years later, we have found eleven of these, ten of which came from black holes. Here’s what we learned.
There were two “run” the LIGO data: the first from 12 September 2015 to 19 January 2016 and the second, with improved sensitivity, from 30 November 2016 to 25 August 2017. The last launch, in particular, was held in conjunction with the VIRGO detector in Italy, which added not only a third detector, but also significantly improved our ability to mark the place of occurrence of these gravitational waves. LIGO is currently not working, is closed for renovation updates that will make it even more sensitive. A new session of data collection should begin in the spring of 2019.
November 30, LIGO scientific collaboration has published the results of their improved analysis, which is sensitive to the last stages of the merger objects with mass from 1 to 100 solar.
Of the 11 discoveries that have been made to date, represent 10 of the merger of black holes, and only GW170817 is the merger of neutron stars. The merger of neutron stars was closest to us — only 130-140 million light years. The massive fusion GW170729 — we heard from a distance of 9 billion years.
Two of these detect are also the easiest and most difficult merger with the formation of gravitational waves: GW170817 faced a neutron star with a mass of 1.46 and 1.27 sun and GW170729 faced black holes with a mass at 50.6, 34.3 solar masses.
Before you are five surprising facts that we learned, thanks to all these discoveries.
#1. Big is not always seen better
The biggest merger of black holes is the easiest to see — and they are not more than 50 solar masses. Gravitational waves are good because they are easier to see from far away than the light source. The light loses its brightness is proportional to the square of the distance: a star is ten times further away, will be a hundred times dimmer. But gravitational waves are damped proportionally to the distance: black holes that are at this distance, will produce 1/10 and not 1/100 the signal strength.
As a result, we can see a very massive objects at very large distances, but cannot see black holes merging at 75, 100, 150 or 200+ solar masses. From 20 to 50 solar masses — quite common, but above that we haven’t seen anything yet. Perhaps black holes coming from supermassive stars are indeed rare.
#2. More detection is better
Adding a third detector at the same time improves the ability to determine the positions of the objects and increases the frequency of detection. LIGO worked for about 4 months during the first run and 9 months during the second year. However, half of the detections occurred in the last month: she worked with VIRGO. In 2017 gravitational-wave events were detected in these days:
- July 29 (black holes of solar mass and 50.6 34.3),
- August 9, (the black holes of solar mass and 35.2 23.8),
- 14 Aug (black holes of solar masses 30.7 and 25.3),
- August 17 (the neutron star of solar mass 1.46 and 1.27),
- August 18 (the black holes of solar masses of 35.5 and 26.8),
- August 23 (black holes of solar mass and 39.6 29.4).
During this last month of observations, we find the merger more than once a week. Maybe when we become sensitive to large distances and the signals of smaller amplitudes and masses, we begin to see one event per day in 2019.
#3. Merging black holes lights up the Universe
When black holes that we found, faced, they released more energy at the peak than all the stars in the Universe combined. Our Sun is a standard that shapes our view of other stars. It shines so brightly that its total energy is 4 x 1026 watts — equivalent transformation of four million tons of matter into pure energy every second.
In the evaluation of ~1023 stars in the observable Universe, the total power output of all the stars shining in the sky, exceed 1049 watts at any time: a huge amount of energy distributed throughout space. But within a few milliseconds during the peak of the mergers of double black holes, each of the 10 observed events from the point of view of energy, eclipsed all the stars in the Universe combined. (Although this number is relatively small). It is not surprising that the most massive mergers topped the list.
#4. Energy generators
About 5% of the total mass of both black holes is transformed into pure energy according to Einstein’s formula E = mc2 in these mergers. Ripples in space that produce these merging black holes, must be somewhere to get energy and somehow must come from the masses themselves merging black holes. On average, on the basis of magnitudes of signals of gravitational waves, which we have seen and recovered the distance, black holes lose about 5% of its total mass, which turns into gravitational wave energy, if the merger.
- GW170608, merging black holes with the lowest mass, was converted to 0.9 solar masses into energy.
- GW150914, the first radiance of black holes, transformed a 3.1 solar masses into energy.
- GW170729, the most massive black holes, transformed a 4.8 solar masses into energy.
These events are causing ripples in space-time, represent the most energetic events known since the Big Bang. They produce more energy than any neutron star mergers, gamma-ray bursts or supernovae.
#5. More smaller — soon
With all that we have by now seen, you can expect that we will see mergers of black holes with less mass and greater frequency. The most massive mergers of black holes produce signals with the largest amplitude, so they are the easiest to detect. But given the fact, how are the volume and distance, double the distance means eight times the volume. The more sensitive LIGO becomes, the easier it is to detect massive objects at greater distances than low-mass objects nearby.
We know that there are black holes at 7, 10, 15 or 20 solar masses, but LIGO is easier to detect more massive black hole away. We expect that there are double black holes with different masses: one of them will be much more massive than the other. As soon as improved our sensitivity, we expect that there will be more, but the easiest would be to find the most massive. We expect that the most massive of them will dominate in the first discoveries, as well as “hot Jupiters” dominated in the first search of exoplanets. As for how we will improve the search process, we will find more black holes with less mass.
When it was announced about the discovery of the first gravitational waves, together with this born gravitational wave astronomy. People have compared this event with the fact, when Galileo first turned his telescope to the heavens, but in reality it is much more. As if our skies were covered with clouds, we first developed a device that allows you to see through them bright enough source of gravity: mergers of black holes or neutron stars. The future of gravitational wave astronomy promises to upend our view of the Universe, to show her in a new light. And this future has already arrived.
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