Free Astronomy Magazine November-December 2018

36 NOVEMBER-DECEMBER 2018 SPACE CHRONICLES Astronomers propose a new method for detecting black holes by IAC A stellar-mass black hole is a compact object with a mass greater than 3 solar masses. It is so dense and has such a power- ful force of attraction that not even light can escape from it. That is why it cannot be observed directly, but only via the effects it produces, in the present case on its companion star, from which it “feeds”. In gen- eral when matter falls onto a black hole is does so “quietly” by way of an accretion disc. However, there are periods when this in fall is violent, and “bursty”, producing a strong outburst of X-ray brightness. Binary systems composed of a star donating mass to a black hole are es- sential laboratories for the under- standing of the most extreme physical phenomena in the universe, such as those which, towards the end of the life of a massive star lead to the formation of the black hole it- self, or to a neutron star. Until now some 60 candidates for this type of black holes have been found in our Galaxy, thanks to the detection of A rtist’s impression of astrophysi- cal jets emitting from the binary system V404 Cygni. [Gabriel Pérez Díaz, Multimedia systems (IAC)]