Binary stars are pairs of stars sufficiently close to each other to be held together by their mutual gravitational attraction (like the Earth and the Moon), revolving in orbit around their common centre of gravity. Such pairs of stars are exceedingly common throughout the Universe.

Many interacting binaries are thought to be black hole candidates, as their supposed masses seem to be greater than the mass attributed to neutron stars. One expects binaries to behave differently according to whether the compact object is a neutron star or a black hole. Thanks to the greatly improved observational instruments used by INTEGRAL, astrophysicists hope to be able to distinguish one from the other through their gamma-ray emissions, thus, proving the existence of black holes.

Galactic Centre