Subo Dong, Zexuan Wu, Yoon-Hyun Ryu, A. Udalski, P Mróz, Krzysztof A. Rybicki, Simon T. Hodgkin, Ł. Wyrzykowski, L. Eyer, T. Bensby, Ping Chen, Sharon X. Wang, Andrew Gould, Hongjing Yang, Michael D. Albrow, Sun-Ju Chung, Cheongho Han, Kyu-Ha Hwang, Youn Kil Jung, In-Gu Shin, Yossi Shvartzvald, Jennifer C. Yee, Weicheng Zang, Dong-Jin Kim, Chung‐Uk Lee, Byeong-Gon Park, R. Poleski, J. Skowron, M. K. Szymański, I. Soszyński, P Pietrukowicz, S Kozłowski, D. M. Skowron, K. Ulaczyk, Mariusz Gromadzki, M. Ratajczak, Patryk Iwanek, Marcin Wrona, Mateusz J. Mróz, Guy Rixon, D. L. Harrison, E. Breedt
A population of free-floating planets is known from gravitational microlensing surveys. None have a directly measured mass, owing to a degeneracy with the distance, but the population statistics indicate that many are less massive than Jupiter. We report a microlensing event-KMT-2024-BLG-0792/OGLE-2024-BLG-0516, which was observed from both ground- and space-based telescopes-that breaks the mass-distance degeneracy. The event was caused by an object with [Formula: see text] Jupiter masses that is either gravitationally unbound or on a very wide orbit. Through comparison with the statistical properties of other observed microlensing events and predictions from simulations, we infer that this object likely formed in a protoplanetary disk (like a planet), not in isolation (like a brown dwarf). Dynamical processes then ejected it from its birthplace, producing a free-floating object.