A free-floating-planet microlensing event caused by a Saturn-mass object

• 成果类型: Article
• 署名作者: Dong, Subo; Wu, Zexuan; Ryu, Yoon-Hyun; Udalski, Andrzej; Mroz, Przemek; Rybicki, Krzysztof A.; Hodgkin, Simon T.; Wyrzykowski, Lukasz; Eyer, Laurent; Bensby, Thomas; Chen, Ping; Wang, Sharon X.; Gould, Andrew; Yang, Hongjing; Albrow, Michael D.; Chung, Sun-Ju; Han, Cheongho; Hwang, Kyu-Ha; Jung, Youn Kil; Shin, In-Gu; Shvartzvald, Yossi; Yee, Jennifer C.; Zang, Weicheng; Kim, Dong-Jin; Lee, Chung-Uk; Park, Byeong-Gon; Poleski, Radoslaw; Skowron, Jan; Szymanski, Michal K.; Soszynski, Igor; Pietrukowicz, Pawel; Kozlowski, Szymon; Skowron, Dorota M.; Ulaczyk, Krzysztof; Gromadzki, Mariusz; Ratajczak, Milena; Iwanek, Patryk; Wrona, Marcin; Mroz, Mateusz J.; Rixon, Guy; Harrison, Diana L.; Breedt, Elme
• 署名单位: Peking University; Peking University; Chinese Academy of Sciences; Nanjing Institute of Geology & Paleontology, CAS; National Astronomical Observatory, CAS; Korea Astronomy & Space Science Institute (KASI); University of Warsaw; Weizmann Institute of Science; University of Cambridge; University of Geneva; Lund University; Zhejiang University; Zhejiang University; Tsinghua University; Max Planck Society; University System of Ohio; Ohio State University; Westlake University; University of Canterbury; Chungbuk National University; Smithsonian Institution; University of Warwick; Villanova University; University of Cambridge
• 刊物名称: SCIENCE
• ISSN/ISSBN: 0036-8075; 1095-9203
• DOI: 10.1126/science.adv9266
• 发表日期: 2026-01-01
• 页码: 96-99
• 关键词: gravitational lensing experiment; GALACTIC BULGE; PARALLAX; stars; spitzer; EVOLUTION; disk; spectroscopy; TELESCOPES; RESOLUTION

摘要

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.