Extreme Solar Systems with Roman: solar system analogs, low-mass free-floating planets, giant moons, and circumbinary planets

The Nancy Grace Roman Space Telescope, or Roman, is NASA’s next large astrophysics mission, due to be launched in late 2026 or early 2027. One of the main surveys during the Roman prime mission will be the Roman Galactic Bulge Time Domain Survey (RGBTDS), which will monitor ~2 sq. degrees toward the Galactic center in a wide 1-2 micron filter with Hubble-like angular resolution, at a cadence of ~15 minutes over 6 seasons of 62-72 days, for a total survey duration of 372-432 days. The RGBTDS is expected to detect tens of thousands of microlensing events, including ~1500 cold bound planets and hundreds of free-floating planets. Due to the large number of events, uniform cadence, exquisite photometry and control of systematics, and the ability to monitor small stars, Roman will be sensitive to microlensing exotica that are poorly probed or unexplored from the ground. These include events due to analogs of all four of the giant planets in our solar system, very low-mass free-floating planets, giant moons, and circumbinary planets.