The Universe shudders again.

The detectors of gravitational waves, LIGO, have again felt a shudder in space-time. The event, merger of two black holes, has emitted as much energy in just one second as the whole the universe

Courtesy of LIGO-Caltech

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Courtesy of Physical Review Letters. The plot shows the oscillations in the distance measured for the second detection of gravitational waves (GW151226). The lower plot shows the frequency of the oscillation, and how it increases as the two black holes approach and then, once merged, the oscillations disapear.

For the second time in three months, LIGO detectors have detected gravitational waves, from the merger of two black holes. These exotic astronomical objects, in an accelerated dance, rotating around each other at a rate of about 55 revolutions per second, have been merged into a final black hole, of 21 solar masses. In this process they have emitted an enormous amount of energy. In one second they have released as much energy as if the whole mass of the Sun was transformed into energy in that fraction of time, or equivalently, the energy emitted by all the stars in the universe in that second.

Gravitational waves were predicted by Albert Einstein in 1916, and were first detected a few months ago. These waves distort space and time. In order to do this, it is required an energy that only the most exotic objects in the universe can deliver. Another source of gravitational waves was the Big Bang itself. But when these waves reach our detectors on Earth (1.4 billion light years in this case), they arrive so weakened, that they are extremely difficult to detect. The  required measurement is equivalent to measuring the distance between the Earth and the Sun with an accuracy of a few atoms.

When gravitational waves traverse the Earth, or its detectors, or you and me,  they expand and contract the distances between atoms. These oscillations they create are related to the movement of the two black holes that originated them. The intensity of the oscillations, their frequency and their evolution, can give us a lot of information from the event.
​The announcement of the first detection was the starting point of gravitational wave astronomy. Until then, all information from the universe came though electromagnetic waves: light. We now have another source of information, another way to scan the cosmos. This new window can reach where light does not reach. With gravitational waves we can see black holes, and maybe we can get to watch the Big Bang.

This new detection, the second in three months, begins to indicate how many of these phenomena are taking place in the Universe, and will help us to determine the density of black holes in the universe. This is important for models of galaxy evolution and to extend our knowledge of the history of the universe.

We are witnessing a new era in astronomy. we are beginning to fell the shudders of the Universe, a if we were Darth Vader feeling the presence of the force.

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