Overview
- A peer-reviewed study in Science led by Subo Dong reports the first precise mass measurement of a starless, free-floating planet using dual-vantage microlensing.
- Separate observations from ground telescopes and the Gaia spacecraft captured the event with a slight timing difference, enabling a microlensing parallax that resolves mass and distance.
- The planet is about 0.22 times Jupiter’s mass—roughly Saturn-sized—and sits roughly 9,800 light-years from Earth toward the Milky Way’s center.
- The researchers say the planet’s properties are consistent with formation in a planetary system followed by ejection into interstellar space.
- The result demonstrates a method that upcoming wide surveys, including NASA’s Nancy Grace Roman Space Telescope, could use to identify and characterize many more rogue planets.