Four months after David Reitze’s announcement – “We have detected gravitational waves” – the stations of the Large Laser Interferometer Gravitational-Wave Observatory (LIGO) have detected for the second time, produced this time by the fusion of two black holes. The event dates back to December 26th, 2015 (3:38:53 am Greenwich time) and involved black holes of 14 and 8 solar masses that gave rise to a single black hole of 21 solar masses. As we can well guess, the energy corresponding to the only missing mass is responsible for the formation of the waves themselves. The first event of September 14, 2015 had involved much larger black holes: the final black hole. The result of the sum of the two, should have measured 65 solar masses, three of which, for the aforementioned reason, have contributed to upsetting the plot of space time.
Because of the masses at stake in the event, recorded with the name of GW151226 and occurred 1.4 billion light years from Earth, this time the signal picked up was weaker and longer, about a second, corresponding to the last 55 orbits of the two black holes around the common center of gravity.
The official announcement
The official announcement of the new observation of gravitational waves occurred jointly by the LIGO-VIRGO collaboration on June 15th, 2016 at the convention of the American Astronomical Society in San Diego. The data collected by the two American interferometers were elaborated by the physicists of VIRGO and LIGO and, once accepted, the results were published on the important scientific journal Physical Reviews Letters.
The collaboration of LIGO with VIRGO, the Italian-French antenna placed near Pisa, will be fully operational at the end of 2016, when VIRGO will operate with a higher sensitivity expected after its latest technological update.
Simulation of the gravitational wave emitted by the fusion of two black holes of 14 and 8 solar masses
Watch the video : How VIRGO and LIGO work