Multi-messenger astronomy

Networks

Milestones

• 1940s: Some cosmic rays are identified as forming in solar flares.
• 1987: Supernova SN 1987A emitted neutrinos that were detected at the Kamiokande-II, IMB and Baksan neutrino observatories, a couple of hours before the supernova light was detected with optical telescopes.
• August 2017: A neutron star collision in the galaxy NGC 4993 produced the gravitational wave signal GW170817, which was observed by the LIGO/Virgo collaboration. After 1.7 seconds, it was observed as the gamma ray burst GRB 170817A by the Fermi Gamma-ray Space Telescope and INTEGRAL, and its optical counterpart SSS17a was detected 11 hours later at the Las Campanas Observatory, then by the Hubble Space Telescope and the Dark Energy Camera. Ultraviolet observations by the Neil Gehrels Swift Observatory, X-ray observations by the Chandra X-ray Observatory and radio observations by the Karl G. Jansky Very Large Array complemented the detection. This was the first gravitational wave event observed with an electromagnetic counterpart, thereby marking a significant breakthrough for multi-messenger astronomy. Non-observation of neutrinos was attributed to the jets being strongly off-axis. On 9 December 2017, astronomers reported a brightening of X-ray emissions from GW170817/GRB 170817A/SSS17a.
• September 2017 : On September 22, the extremely-high-energy neutrino event IceCube-170922A was recorded by the IceCube Collaboration, which sent out an alert with coordinates for the possible source. The detection of gamma rays above 100 MeV by the Fermi-LAT Collaboration and between 100 GeV and 400 GeV by the MAGIC Collaboration from the blazar TXS 0506+056 was deemed positionally consistent with the neutrino signal. The signals can be explained by ultra-high-energy protons accelerated in blazar jets, producing neutral pions and charged pions. This is the first time that a neutrino detector has been used to locate an object in space and a source of cosmic rays has been identified.