Related Experiment Video
Updated: Jan 7, 2026
06:48
Surface Mapping of Earth-like Exoplanets using Single Point Light Curves
Published on: May 10, 2020
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A free-floating-planet microlensing event caused by a Saturn-mass object
Subo Dong1,2,3, Zexuan Wu1,2, Yoon-Hyun Ryu4
1Department of Astronomy, School of Physics, Peking University, Beijing, China.
Science (New York, N.Y.)
|January 1, 2026
Summary
Astronomers measured the mass of a free-floating planet using gravitational microlensing. This ejected planet, likely formed in a protoplanetary disk, offers new insights into planetary system dynamics.
Area of Science:
- Exoplanetary Science
- Gravitational Microlensing
- Astrophysics
Background:
- Free-floating planets (FFPs) are detected via gravitational microlensing, but their masses are typically unconstrained due to a mass-distance degeneracy.
- Statistical analyses suggest many FFPs are less massive than Jupiter, implying formation within protoplanetary disks.
Purpose of the Study:
- To report the first direct mass measurement of an FFP by breaking the mass-distance degeneracy.
- To determine the formation mechanism (planetary vs. isolated) of a specific FFP.
Main Methods:
- Utilized a joint ground- and space-based observation campaign for the microlensing event KMT-2024-BLG-0792/OGLE-2024-BLG-0516.
- Analyzed microlensing light curves to resolve the mass-distance degeneracy.
Main Results:
- Measured the mass of the lensing object to be approximately 1.1 Jupiter masses.
- The object is either gravitationally unbound or on a very wide orbit, consistent with an ejected planetary-mass object.
Conclusions:
- The observed FFP likely formed in a protoplanetary disk and was subsequently ejected by dynamical processes.
- This finding supports the theory that a significant population of FFPs originates from planetary formation mechanisms.
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