In fact, every time a new instrument capable of exploring the sky was invented, astronomers had to rethink their understanding of space. Recently, scientists have revolutionized astronomy by discovering how to monitor gravitational waves using new technologies including lasers and mirrors.
Black holes are the envelopes of massive stars with such a strong gravity that even light can not escape. When they collide, they release energy into a form called gravitational waves. Collisions which are totally invisible to the naked eye and do not register in the electromagnetic spectrum can only be detected by observing gravitational waves. While Albert Einstein predicted in 1916 that the waves existed, it took almost a century when students actually observed them.
On September 14, 2015, the whole universe was shaken. Well, it is actually more accurate to say that this is the date when humanity has realized a catastrophic event – the merger of two huge black holes that occurred about 1.3 billion years ago, or the stealing of a Star Wars line long ago in a distant, distant galaxy.
Since the gravitational waves, which were released during the merger of black holes 1,3 billion years ago, were washed over the solar system, the very fabric of space and time were compressed and stretched.
Two L-shaped detectors in LIGO laser interferometers in Louisiana and Washington were working together at the first gravitational wave observation. With wave transition, each hand of the L-shaped detector, measuring 2.5 miles in length, is extended and shortened by a distance of about one thousandth of the diameter of the proton. To give you a sense of scale, this is the equivalent of measuring the distance from here to the next Alpha Centauri star with the accuracy of the human hair width.
Now, with the help of another facility in Italy called Virgo, scientists are exploring the common properties of these black hole clashes and where they are taking place. Gravitational waves travel at the speed of light, so when they pass through the Earth, there is little delay between each detector that marks their passage. This delay is used to determine the location in the sky where the crash occurred. The technique is similar to the way geologists use earthquake arrival times in different seismographs to detect the origin of the earthquake.
With LIGO and Virgo detectors, scientists can better understand what happens when very heavy astronomical bodies encounter. The collision of neutron stars, which are scales of stars slightly smaller than black holes, can also cause gravitational waves found on Earth. And, of course, a black hole can also merge with a neutron star.
In newly released paper gravitational wave astronomers describe 11 of these clashes – four of which have never been announced before – as the detectors started operating in 2015. Given the downtime when the equipment was not in operation, one detection every 15 days. In the most impressive example, two massive black holes merged to create one that is about 80 times the mass of the sun, making it the heaviest star black hole ever seen.
For a second, the collision released more energy than any of the light released by every star in the entire visible universe. It was a huge thing. And all this happened in a galaxy located at 9 billion light-years.
Prior to LIGO's first observation, scientists did not think stars could form black holes with masses of about 15 or 20 times heavier than the sun. So, with just 11 observations, scientists are already forced to rethink their theories.
While the announcement of a super massive black hole makes a good headline, this recent book has less stunning but more scientifically significant impact. Finding one thing can be a curiosity. But several events later, scientists can begin to draw some conclusions.
By combining the detector's familiar ability to work with the observed locations and the speed at which they are detected, astronomers can begin to say how often they appear. While scientists are working with a small sample size, they now estimate that in the sphere of space, somewhere between half a billion and a billion light-years, we can expect to see a merger of black holes per year.
And the story is not complete. Detectors are currently offline, subject to upgrades that will allow them to watch twice as far away from the Earth. This will allow them to investigate a volume that is eight times larger than before. The days of the gravity wave astronomy are at their very beginning and there is no doubt that there are huge surprises ahead.