In fact, whenever a new instrument capable of studying the heavens was invented, astronomers had to rethink their understanding of the cosmos. More recently, scientists have provoked a revolution in astronomy, discovering how to observe gravitational waves with the help of new technologies involving lasers and mirrors.
Black holes are the shells of massive stars with gravity so strong that even light can not escape them. When they collide, they release energy in a form called gravitational waves. The collisions, which are totally invisible to the naked eye and are not recorded in the electromagnetic spectrum, can be detected only by the observation of gravitational waves. While Albert Einstein predicted in 1916 that the waves existed, it took almost a century for scientists to actually observe them.
On September 14, 2015, the whole universe shook. Well, in fact, it is more accurate to say that this was the date when humanity became aware of a cataclysmic event – the merging of two huge black holes that occurred about 1.3 billion years ago – or stealing a line of Star Wars. long ago in a galaxy far, far away. "
As the gravitational waves that were released during the merger of the black hole 1.3 billion years ago flooded the solar system, the very structure of space and time became compressed and stretched.
Two L-shaped detectors at Gravitational Wave Observers with Laser Interferometer (LIGO) in Louisiana and Washington worked together on the first observation of a gravitational wave. As the wave passed, each arm of the L-shaped detector, measuring 2.5 kilometers in length, lengthened and shortened by a distance of about a thousandth the diameter of a proton. To give a sense of scale, it's the equivalent of measuring the distance from here to the next Alpha Centauri stellar system with an accurate human hair width.
Now, with the help of another facility in Italy called Virgo, scientists are studying the general properties of these black hole collisions and where they are occurring. Gravitational waves travel at the speed of light, and as soon as they pass Earth, there is a slight delay between the moment each detector observes its passage. This delay is used to help determine the location in the sky where the collision occurred. The technique is similar to the way geologists use earthquake arrival times on different seismographs to locate the source of the earthquake.
With LIGO and Virgo detectors, scientists can better understand what happens when very heavy astronomical bodies collide. The collision of neutron stars, which are shells of stars a little smaller than black holes, can also trigger gravitational waves detected on Earth. And, of course, a black hole could also merge with a neutron star.
In a recently released article, gravitational wave astronomers have detailed 11 of these collisions – four of which had never been announced before – since the detectors began operating in 2015. Taking into account the downtime when the equipment was not operational, a detection every 15 days. In the most striking example, two massive black holes merged to create one that is about 80 times the mass of the Sun, making it the largest black hole ever observed.
For a fraction of a second, the collision released more energy than the light released from all the stars of the entire visible universe. That was a huge thing. And it all happened in a galaxy located 9 billion light-years away.
Before LIGO's first observation, scientists did not believe that stars could form black holes with masses larger than 15 or 20 times heavier than the sun. Thus, with only 11 observations, scientists have already been forced to reconsider their theories.
Although the announcement of a supermassive black hole is a good headline, this recent article has a less impactful yet more scientifically significant impact. The observation of one thing can be a curiosity. But several later occurrences, scientists may begin to draw some conclusions.
By combining the known detector performance capabilities with the observed locations and the rate at which they are detected, astronomers can begin to tell how often they occur. While scientists are working with a small sample, they now estimate that in a sphere of space between half a billion and a billion light-years, we can expect a merger of black holes per year.
And the story is not over. The detectors are currently offline, undergoing updates that will allow them to peer twice as far from Earth. This will allow them to investigate a volume eight times larger than before. The days of gravitational wave astronomy are in their infancy and no doubt there are big surprises ahead.