SpaceTime

Image: Merging black holes. Credit: NASA Recently it has been suggested that electromagnetic signals detected by Fermi GBM could be associated with the merger of the two black holes detected by LIGO ( GW150914 ).

Image: Simulation of two colliding black holes. Animation created by SXS, the Simulating eXtreme Spacetimes (SXS) project (http://www.black-holes.org) - Caltech LIGO If the GW signal observed by LIGO is due to the merger of two isolated black holes (BHs) in vacuum, no electromagnetic counterparts are expected. However, Fermi observed a signal 0.4 s after LIGO in a region of space compatible with the GW source.

Image: Two black holes are entwined in a gravitational tango in this artist's conception. Credit: NASA A binary black hole (BBH) is a system consisting of two black holes in close orbit around each other. Binary black holes are often divided into stellar binary black holes, formed either as remnants of high-mass binary star systems or by dynamic processes and mutual capture, and binary supermassive black holes believed to be a result of galactic mergers.