Basic physics teach us that black holes are incredibly dense. An interesting type of type of black hole is the stellar mass black hole, which has a mass larger than the sum of three solar masses. They are so dense and generate such a massive pull that it absorbs light completely. This renders them mostly invisible, as we need an additional phenomenon to happen, the consumption of a companion star for example, in order to spot it. Usually, dark holes consume matter in a ‘’silent’’ manner through the accretion disc. Sometimes, the process becomes more violent, emitting an intense burst of X-ray radiation.
Some researchers believe that binary star systems, which are composed of a black hole and a star that offers material in order to feed the black hole, could be used in order to further understand some of the most intensive events in the universe, like a birth of a neutron star, or the collapse of a dying star into a future black hole.
More than 60 e candidates have been identified, but only 17 have been confirmed as viable study subjects, since the process of validation is dependent upon the movements of the companion star.
What we currently know about the formation and evolution of binary systems is limited by the small number of identified systems. In order to change this situation scientists are focusing on discovering new methods that may allow them to discover binary systems that are not currently emitting system radiation.
One of the new techniques involves will allow researchers to measure the brightness of suitable systems by using a series of filters focused on observing the line of hydrogen H-alpha. This line forms in the accretion field of black hole, and its size indicates the intensity of the gravitational field generated by the black hole.
The method has been tested on four systems, using an array of special filters mounted on ACAM, a custom-made device attached to the William Herschel Telescope. The results were compared with the more direct approach of directly measuring the H-alpha line with the ISIS spectrograph. It was revealed that using filters is practical, which may allow researchers to observe hidden binary systems in the future.