The paper “Analysis of ringdown overtones in GW150914” was highlighted by Physical Review Letters as an Editor’s Suggestion. The paper is authored by professor Vítor Cardoso (Department of Physics – Técnico), in collaboration with Roberto Cotesta and Emanuele Berti (Johns Hopkins University), and Gregorio Carullo (University of Pisa), and aims to address the gravitational “musical notes” produced by black holes.

In the context of atomic physics, the technique used to identify these notes is called spectroscopy, which is also used to study the Sun and other stars. Thus, in the total absence of noise it is possible to use gravitational waves “to hear the shapes of black holes”.

The authors demonstrated that the sound emitted form black holes in the presence of noise presents unexpected complications, and that gravitational wave detectors and more advanced data analysis techniques are needed to do black hole spectroscopy.