A free-floating-planet microlensing event caused by a Saturn-mass object
- Subo Dong
- Zexuan Wu
- Yoon-Hyun Ryu
- Andrzej Udalski
- Przemek Mróz
- Krzysztof A. Rybicki
- Simon T. Hodgkin
- Łukasz Wyrzykowski
- Laurent Eyer
- Thomas 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
- Radosław Poleski
- Jan Skowron
- Michał K. Szymański
- Igor Soszyński
- Paweł Pietrukowicz
- Szymon Kozłowski
- Dorota M. Skowron
- Krzysztof Ulaczyk
- Mariusz Gromadzki
- Milena Ratajczak
- Patryk Iwanek
- Marcin Wrona
- Mateusz J. Mróz
- Guy Rixon
- Diana L. Harrison
- Elmé Breedt
2026-01-01
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 0.219 − 0.046 + 0.075 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.