The Dynamic Infrared Sky
The dynamic infrared sky is hitherto largely unexplored. I will present the SPitzer InfraRed Intensive Transients Survey (SPIRITS) −−− a five-year systematic search of 194 nearby galaxies within 30 Mpc, on timescales ranging between a week to a year, to a depth of 20 mag with Spitzer's IRAC camera. SPIRITS has already uncovered over 137 explosive transients and over 2400 strong variables. Of these, 72 infrared transients are especially interesting as they have no optical counterparts whatsoever even with deep limits from Keck and HST. Interpretation of these new discoveries may include (i) the birth of massive binaries that drive shocks in their molecular cloud, (ii) stellar mergers with dusty winds, (iii) 8--10 solar mass stars experiencing e-capture induced collapse in their cores, (iv) enshrouded supernovae, or (v) formation of stellar mass black holes. SPIRITS reveals that the infrared sky is not just as dynamic as the optical sky; it also provides access to unique, elusive signatures in stellar astrophysics. I conclude with my plans of building a wide-field infrared imager dedicated to opening the infrared time-domain.