Prospects for the Detection of Exomoons Transiting Planetary Mass Objects with Infrared Space-Based Observatories

The detection and characterization of the exomoon population would open the door to a new field within exoplanetary science. We present the prospects for the James Webb and the Nancy Grace Roman Space Telescopes (JWST & Roman) to detect exomoons transiting isolated planetary-mass objects (IPMOs — also known as free-floating planets). Given the high occurrence and close orbits of solar system moons, transiting exomoons are likely to occur around 10%-15% of IPMOs, although the intrinsic variability of the IPMO may make detections challenging. For at least 30 of the currently known nearby IPMOs, observations of a single transit with JWST would allow for the detection of an Io- or Titan-sized moon. Beyond JWST, we propose that a Transiting Exosatellites, Moons & Planets in Orion (TEMPO) survey with Roman could monitor hundreds of IPMOs and brown dwarfs in the Orion Nebula Cluster for transits. A 30-day survey could detect a dozen “Super-Titans” (Titan to Earth-sized moons) transiting 1-13 MJup IPMOs as well as ~50 exosatellites transiting brown dwarfs. The TEMPO survey would be capable of providing the first census demographics of IPMO and brown dwarf exosatellite populations. Archival Spitzer data also offers an opportunity to search for IPMO exomoons. We discuss our upcoming exosatellite transit survey of archival Spitzer substellar light curves as well as future opportunities for follow-up of our recently discovered 1.7 earth-radii habitable-zone exomoon candidate in the 2MASS J1119-1137AB system.