– Precise Measurement of Distance and Mass through Simultaneous Ground and Space Observations
The Korea AeroSpace Administration (KASA, Administrator Yoon Youngbin) announced on Friday, January 2, 2026, that an international research team, including the Korea Astronomy and Space Science Institute (KASI, President Jang Hyun Park), has discovered a Saturn-mass "rogue planet" by utilizing Korea's Microlensing Telescope Network (KMTNet) and the European Space Agency’s Gaia space telescope.
Rogue planets are celestial bodies that have escaped the gravitational pull of a host star and drift alone through space. These objects provide crucial clues to understanding the formation and evolution of planetary systems. The newly discovered rogue planet, named 'KMT-2024-BLG-0792', is approximately 0.7 times the mass of Saturn and is located about 10,000 light-years from Earth. Notably, this discovery marks the first time a rogue planet’s precise distance from Earth has been measured through the simultaneous use of both ground-based and space-based telescopes.
Currently, gravitational microlensing* is the only method capable of detecting rogue planets. KMTNet, which operates three telescopes in Chile, Australia, and South Africa, enables continuous 24-hour observation, allowing it to capture the short-lived microlensing events caused by rogue planets. The KASI KMTNet team detected this rogue planet through a microlensing event, and by analyzing data from the Gaia space telescope―which observed the same region six times over 16 hours during the event―they were able to accurately determine the planet's distance and mass.
* Gravitational Microlensing: A phenomenon where the gravity of an invisible foreground object bends the light from a distant background star, causing a temporary increase in its brightness.
This discovery holds significant academic importance. Previously, all nine rogue planets discovered via the microlensing method were found outside a specific range of the Einstein radius* known as the "Einstein Desert" (approx. 9-25 microarcseconds). This planet is the first case ever discovered within the Einstein Desert.
* Einstein Radius: A physical radius defining the extent to which the gravitational field of a lens object bends light
"Thanks to the exceptional performance of KMTNet established by KASI, South Korea is leading the field in discovering exoplanets, including rogue planets, through the microlensing method," said Kyung-in Kang, Director General of the Space Science Exploration Directorate at KASA. "We will continue to pursue new discoveries through simultaneous observations involving our ground-based telescopes and international space missions."
The findings of this study was published in the journal Science on January 1, 2026 (EST).