There are observational and theoretical reasons to suspect that up to 10s of percent of massive stars that undergo core-collapse at the end of their lives fail to explode in a canonical energetic supernova 

Powerful jets from active galactic nuclei (AGNs) are observed on scales from Mpc down to astronomical units, from essentially all observable wavebands and via multi-messengers.

Stars form in dense clouds of gas and dust, and this material greatly obscures the central cores of still-forming stars. However, some radiation does escape from their circumstellar envelopes and disks, allowing some study of these youngest stars. This even includes Class 0 protostars, stars so young that they have yet to accrete the majority of their mass. We have recently observed the first absorption spectrum of the photosphere of a Class 0 protostar, S68N in Serpens.

The Kepler and K2 missions blessed the community with a plethora of planet transit detections which enabled studies of exoplanet size demographics. Much of the recent progress in this field is driven by improved characterization of the stellar hosts. Our group recently used precise radius measurements from the California-Kepler Survey (CKS) to detect a gap in the distribution of planet radii.