Multi-messengers including neutrinos, gravitational waves, photons and cosmic rays are expected to be produced during astronomical catastrophic events such as supernova and merging of two neutron stars. Among those messengers, the origin of cosmic rays remains elusive despite their discovery made more than a century ago. This is mainly due to their charged nature, which makes them extremely difficult to trace across the Universe. It is commonly believed that cosmic rays are accelerated in highly magnetized jets which are often associated with transient exploding phenomena such as AGN flaring. Therefore, real-time multi-messenger observation of an astronomical transient event can provide a holographic picture of the complicated physics processes occurred. In particular, the observation of high-energy astrophysical neutrinos can be the “smoking gun” evidence for cosmic ray origin. In this talk, I will give an overview on the current status of neutrino astronomy.
