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And two! For the second time, very special detectors on Earth trembled when passing jolts from outer space: gravitational waves. These are vibrations of spacetime equivalent to the ripples created by the fall of a pebble on the surface of a lake and are described by the theory of general relativity of Albert Einstein.
Their oscillating propagation has the ability to slightly distort the distances, but only high-performance instruments can detect these small changes, the order of the size of an atom. Since February 11, physicists have however proved that it was possible. That day, the team of the LIGO instrument using both of these devices installed in the United States, in Livingstone (Louisiana) and Hanford (Washington), announced seeing them jump to the passage of these waves.
Rebelote June 15 at the meeting of the American astronomical Society in San Diego (California). The same collaboration, which also includes the European team whose Virgo detector, stopped to work, installed near Pisa, Italy, said it had identified a second tremor felt 26 December 2015. “It’s a relief to be able to have a confirmation on different phenomena” , says Nicolas Arnaud, CNRS researcher at the laboratory of the Orsay linear Accelerator, a member of Virgo.
Read: gravitational waves detected a century after it was predicted
the “pebble” cosmic that wrinkled the surface of the space-time
this shock only lasted a second, but it was enough to determine what “rock” cosmic has wrinkled the surface of spacetime and hit both switches with 1.1 millisecond shift . As for the first event, there are two black holes rotate at high speed around each other and eventually merge to form a new black hole.
newborn born after the bustle of birth, stops vibrating like a bell and emits more gravitational waves. Such masses and these speeds are sufficient to shake the cosmic environment on Earth to feel even more than a billion years after the event took place.
Both game masses are 7.5 and 14 times that of the Sun and the resulting object weighs 20.8 times more than our star, lost ground having been carried away by the gravitational wave as energy. The two black holes turning around are lighter than those announced in February, who were 29 and 36 times the mass of the sun. They were therefore more difficult to spot. Some 55 spirals before fusion were recorded against ten in the first case. Unfortunately, as for the first duo, the location of this waltz in the Universe is unclear because both sensors are not enough to precisely indicate the region of origin.
the frequency of such events is larger than expected
a third tremor was also recorded October 12, 2015, but it is not assigned to a gravitational wave, precision fault sufficient. “No other candidate pair of black holes mass of between 4 and 100 times that of the Sun has been found until the end of the data taking in January 2016″ , the researchers write in their article Physical Review Letters published June 15 However, they feel already that the frequency of such events is greater than expected, on the order of one per month.
Finally, they confirm that “this first observation period announces opening of astronomy by gravitational waves “. These detectors, from the autumn, will indeed become real telescopes, spotting events completely invisible until then, since black holes by definition does not radiate light. At this time, the Virgo detector will be getting a facelift to be as accurate as LIGO. At three, together, they can triangulate events and more accurately locate their origin in the sky.
A giant gravitational wave detector
This will also the time when the European Space Agency will finalize its draft giant gravitational wave detector, ELISA. It should work in space before 2030 with laser arm more than a million kilometers, against 3-4 kilometers on Earth. A first experiment LISA Pathfinder (LPF), launched in December 2015, unveiled in early June of better than expected results regarding the technical feasibility of such a project.
In the ELISA line of sight, he there will be so-called supermassive black holes, with a mass of about a million times that of the Sun and which rotate relatively slowly. The sensor will also see the same couples than those observed by LIGO, but months before their merger during their long duet dance.
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