Systematically Bridging the Gap Between Novae and Supernovae

The venerable study of cosmic explosions is over a century old. However, until recently, there has existed a glaring six-magnitude luminosity gap between the brightest novae and faintest supernovae. Serendipitous discoveries, archival searches and ongoing systematic surveys are yielding optical transients that are fainter, faster and rarer than supernovae. Theorists predict a variety of mechanisms to produce transients in the gap and observers have the best chance of finding them in the local Universe. Here I review the discoveries and the unique physics of cosmic explosions that bridge this gap between novae and supernovae.