The substellar neighborhood: a stunningly diverse population of brown dwarfs within 20pc of the Sun

The census of the coldest constituents of the Solar Neighborhood, here defined as a 20pc-radius sphere around the Solar System, remains incomplete. Completing such census is one of the driving goals for the CatWISE and “Backyard Worlds: Planet Nine” teams, who have discovered hundreds of new nearby late-T and Y dwarfs using data from WISE/NEOWISE. Here I present the results of a multi-telescope observing campaign to characterize these new discoveries. Photometric and astrometric follow-up is revealing a stunning diversity among the substellar population, a diversity that recent atmospheric models suggest is driven by metallicity.