Universe, a powerful landscape unveiled thanks to new gravitational waves

A powerful landscape in the Universe unveiled thanks to the discovery of new gravitational waves. The landscape is made up of real cosmic earthquakes generated by the merger of two black holes or neutron stars or black hole-neutron star pairs. The double discovery was made by the teams of scientists of the gravitational wave observatories Virgo and Ligo who have detected 35 new events in the most recent period of observations and which lead to 90 gravitational waves detected so far. The data, published today in the so-called third Catalog Paper, “sheds light on the characteristics of new populations of black holes, whose masses, together with those of observed neutron stars, provide new clues to the life and death of stars, further expanding the horizons of gravitational astronomy “. The teams of scientists of the Virgo and Ligo collaborations thus take a new step forward in the field of gravitational waves, the ripples in the spacetime fabric theorized by Albert Einstein but first detected only on September 14, 2015. The announcement of the discovery of the waves gravitational forces arrived in February 2016 and had a worldwide echo. Kip Thorne, Barry Barish and Rainer Weiss won the 2017 Nobel Prize in Physics “for their decisive contributions to the Ligo detector and the observation of gravitational waves” defined by some scientists as “new pairs of glasses” aimed at the Universe. Since then, the data of these 35 new gravitational wave events have been observed between November 2019 and March 2020, during the second part of the third and most recent observation period of Ligo and Virgo (O3b) and bring the total number to 90. of gravitational signals detected so far by the global network of three interferometers. Scientists explain that most of the new signals originate from the swirling approach of two black holes until they merge: “Real cosmic earthquakes that shake the fabric of space-time, generating a powerful emission of gravitational waves.” Two other events, one of which already announced last June, were instead “identified as mergers between a neutron star and a black hole, a source observed for the first time in the latter period of observations of Ligo and Virgo. further event, revealed in February 2020, according to scientists “could come from a pair of black holes or from a mixed pair of a black hole with a neutron star.” In fact, the researchers point out, “the mass of the lightest object falls into an interval, the so-called mass gap, where before gravitational revelations neither neutron stars nor black holes were expected to form and therefore remains an enigma for scientists. “These new results were published today by scientific collaborations of Virgo, Ligo and Kagra in the third catalog of transient sources of gravitational waves (Gwtc-3), on the ArXiv online archive. The catalog is accompanied by two other publications focusing on the cosmological and astrophysical consequences of data. “I still vividly remember the enthusiasm of all of us scientists as we listened to the public announcement of the first discovery of gravitational waves in early 2016. Now, less than six years later, the discoveries reported in the Gwtc-3 catalog add valuable new information to the new, growing field of gravitational wave astronomy and provide a new perspective on many aspects of the Universe, such as, for example, binary populations of black holes or neutron stars “says Edoardo Milotti, member of the Virgo collaboration of the University of Trieste and the Infn. The progress made in a few years in the field of gravitational waves “is surprising, passing from the first survey to the observation of a few events per month” and “this was possible thanks to the program of continuous technological updates that have transformed the first pioneering instruments into detectors. increasingly sensitive “underline the scientists. The Ligo and Virgo observatories are in fact “currently undergoing a further update and will begin the next fourth observation period in the second half of 2022 with an even greater sensitivity, corresponding to a volume of the universe almost 10 times larger” and therefore a probability much greater than picking up gravitational signals. Sebastian Steinlechner, assistant professor at the University of Maastricht and Nikhef, explains that “among other updates to Virgo, we have created an additional optical cavity – the so-called signal recycling cavity – which allows us to improve the sensitivity band of the detector to high frequencies. This corresponds to a greater ability of the detector to ‘hear’ the final phases of coalescing pairs, when two black holes or stars merge into one “. Meanwhile, the Kagra detector in Japan is being tested and plans to participate in the next observation period. Expanding the network of detectors capable of jointly taking data will further increase the accuracy of source location, a key feature for future Multi-Message Astronomy developments. And it is an army composed of thousands of scientists active in many countries of the world that is scrutinizing and studying gravitational waves in the context of the gravitational wave observers Virgo, Ligo and Kagra. The Virgo collaboration has 700 members from 129 institutions, around 1,300 scientists in Ligo, over 470 members from 115 institutes in 14 countries in Kagra. (by Andreana d’Aquino)