Mar. 27, 2011 Researchers from the Instituto de Astrofísica de
Canarias (IAC) have discovered the existence of a black hole 5.4
times greater in mass than that of our Sun, located in the X-ray
binary system XTE J1859+226. The observations carried out from
the Gran Telescopio Canarias (GTC), managing to obtain the first
spectroscopic data from this binary system to be published, have
been determinant for the discovery. X-ray binaries are stellar
systems composed by a compact object (which may be a neutron
star or a black hole) and a 'normal' star. The compact object
sucks matter out of the star and adds it slowly to its own mass,
through a spiral disc formed around it. This process of
absorption is known as acretion. Only 20 binary systems, out of
an estimated population of around 5,000 within our Galaxy, are
known to contain a black hole. XTE J1859+226 is, in particular,
a transient X-ray binary located in the Vulpecula constellation.
It was discovered by satellite RXTE during an eruption
registered in 1999.