Intermediate mass black holes. Intermediate mass black holes (IMBH) represent a new category of cosmic black holes which have been long sought by astronomers. Masses of IMBH are thought to be significantly greater than those of stellar-mass black holes but less than supermassive black holes in galactic nuclei. Their typical values range between 102 to 104 solar masses and they could reside in cores of dense globular clusters. Recently, there have been a number of indication that IMBH do exist especially in so-called ultra-luminous X-ray sources, however, the issue remains uncertain and further work is needed to resolve various controversies.
Imaging horizon of a black hole. Title of this article may sound like a contradiction. Cosmic black holes do not emit their own radiation and they cannot be seen in a telescope. But will astronomers be even able to image the immediate vicinity of the black hole horizon, where matter swirles just before plunging into the hole interior? We discuss prospects for future interferometry techniques which will reach sufficient resolving power to show structures of the size of one gravitational radius. This will allow astronomers to detect various processes that occur in plasma as it enters the black hole.