Editorial to the Topical Collection: The Tidal Disruption of Stars by Massive Black Holes

For several decades, astronomers have speculated that a hapless star could wander too close to a super massive black hole (SMBH) and be torn apart by tidal forces. It is only with the recent advent of numerous wide-field transient surveys that such events have been detected in the form of giant-amplitude, luminous flares of electromagnetic radiation from the centers of otherwise quiescent galaxies. These discoveries span the entire electromagnetic spectrum, from γ-rays through X-rays, ultra-violet, optical, infrared, and radio. A small number of events launch relativistic jets. These tidal disruption events (TDEs) have caused widespread excitement as they can be used to study the properties of quiescent, otherwise undetectable, SMBHs; the populations and dynamics of stars in galactic nuclei; the physics of black hole accretion including the potential to detect relativistic effects near the SMBH; and the physics of (radio) jet formation and evolution in a pristine environment. For scientific questions concerning quiescent SMBHs, TDEs are unique probes beyond the local universe. TDEs can also occur around active galactic nuclei (AGNs), although uniquely identifying such an event on top of a bright AGN is difficult.