Multi-messenger astronomy is the coordinated observation and interpretation of multiple signals received from the same astronomical event.
Many types of cosmological events involve complex interactions between a variety of astrophysical processes, each of which may independently emit signals of a characteristic "messenger" type: electromagnetic radiation (including infrared, visible light and X-rays), gravitational waves, neutrinos, and cosmic rays.
The main multi-messenger sources outside the heliosphere are: compact binary pairs (black holes and neutron stars), supernovae, irregular neutron stars, gamma-ray bursts, active galactic nuclei, and relativistic jets.
[4] Lack of any electromagnetic counterpart, for example, could be evidence in support of the remnant being a black hole.
The Astrophysical Multimessenger Observatory Network (AMON),[12] created in 2013,[13] is a broader and more ambitious project to facilitate the sharing of preliminary observations and to encourage the search for "sub-threshold" events which are not perceptible to any single instrument.