Washington (AFP) – An international scientific team said Wednesday it has again detected gravitational waves, which is to date the second observation of this phenomenon predicted by the theory of general relativity Albert Einstein in 1915.
the first direct detection of gravitational waves that had been announced on 11 February a historic event after 40 years of effort that needs to better understand the mysteries of the universe.
This detection was carried out as the first time by the American instrument Ligo (Laser Interferometer Gravitational-Wave Observatory), consisting of two identical detectors four kilometers long, located 3,000 kilometers from each another, Louisiana (south) and in the State of Washington (northwest).
“We know that with this second sense, the properties measured by the Ligo will allow us to begin to answer some of the fundamental questions in gravitational astronomy, as the mystery of the formation of black holes “, welcomed Professor Sheila Rowan, head of the gravitational research Institute of the University of Glasgow, a member of the team research.
These waves result from slight perturbations of the fabric of space-time as a result of the displacement of a massive object, like a weight deforms a net
they observed this time were produced by the merger, there are 1.4 billion years ago, two black holes.
the analysis of data collected on December 26 has determine that they were 14 and 8 times more massive than our Sun, a diameter less than 100 kilometers clarified these astrophysicists.
they announced their detection at the American Astronomical Society conference meeting in San Diego, California. Their work will be published in Physical Review Letters.
The two black holes of the first detection September 14, 2015 had a mass of 29 and 36 times that of the sun.
Well the signal received last December 26 was lower than the first, this second detection is also confirmed with more than 99.99% certainty.
the merger of these black holes generated a quantity ‘energy equivalent to the mass of the sun and was converted into gravitational waves, say the scientists
-. dark and violent phenomenon –
“with the detections of these two phenomena high intensity in four months for our first observation campaign, we can start to make predictions about the possible frequency detection of gravitational waves in the future, “said Albert Lazzarini, of the California Institute of Technology (Caltech) , deputy director of Ligo.
“the Ligo gives us a new approach to observe some of the phenomena of the most obscure but also the most violent in the world,” he added.
in addition to the black holes, it also cited neutron stars, the densest objects in the cosmos.
“We are starting to have an overview of astrophysics new information which may obtain only with gravitational wave detectors, “said David Shoemaker meanwhile, an astrophysicist at the Massachusetts Institute of Technology who led the Ligo modernization program.
he said the first applications are for black holes because they do not emit light and are therefore invisible without gravitational waves.
“the French-Italian Virgo detector, near Pisa, Italy, is currently under stop for improvements. It should restart late in the year and come support the US gravitational wave detectors to improve in particular the identification of their origins, “noted Fulvio Ricci, spokesman for the Virgo scientific team.
the Ligo is also currently in the works to improve its performance. It will resume its observations in September with a sensitivity allowing it to reach 1.5 to 2 times the volume of the universe.
L team of Ligo over a thousand American scientists and fourteen other countries, including a large French contingent of the Centre national de la recherche scientifique (CNRS).
an indirect evidence of gravitational waves was established by the discovery in 1974 of a pulsar and a neutron star rotating around each other at very high speed by Russell Hulse and Joseph Taylor.
This discovery earned them the Nobel prize physics in 1993
. Source: AFP
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