The most important discovery in astronomy in 2017 was the groundbreaking discovery of a gravitational wave event GW170817 due to the merger of two neutron stars as well as its associated short GRB (gamma ray burst) 170817A and
other electromagnetic counterpart emissions in multi-wavelength.
What makes this type of neutrino unique is the fact that unlike its «active»
counterparts that, every now and then, interact with
other matter via the
electromagnetic force, it only interacts gravitationally.