(C) Phys.org

DAEJEON – An international team of astronomers has discovered a "rogue planet"—a world drifting through interstellar space without a parent star—approximately 10,000 light-years from Earth. This newfound celestial body, designated KMT-2024-BLG-0792, is roughly 95 times more massive than Earth, placing it in the mass range of Saturn.

The Korea Aerospace Administration (KASA) announced on Friday that the discovery was made through a joint effort between the Korea Microlensing Telescope Network (KMTNet) and the European Space Agency’s (ESA) Gaia space telescope. The findings were published today in the prestigious international journal Science.

A Milestone in Distance Measurement
While rogue planets are notoriously difficult to detect, this discovery marks the first time researchers have successfully measured the precise distance of such an object using simultaneous observations from both ground-based and space-borne telescopes.

The detection utilized gravitational microlensing, a phenomenon that occurs when the gravity of a foreground object (the planet) acts like a lens, magnifying the light of a distant background star. By analyzing data from KMTNet’s three ground stations in Chile, Australia, and South Africa alongside six distinct observations from the Gaia telescope over a 16-hour period, the team was able to calculate the planet's mass and distance with unprecedented accuracy.

Crossing the "Einstein Desert"
The discovery is scientifically significant for its location within the so-called "Einstein Desert." This term refers to a specific range of Einstein radii (approximately 9 to 25 micro-arcseconds) where very few objects have historically been detected.

"This is the first case of a rogue planet being found within the Einstein Desert," said Lee Chung-uk, a senior researcher at the Korea Astronomy and Space Science Institute (KASI). "Previously, all nine rogue planets discovered via microlensing fell outside this specific range. This finding provides crucial data for understanding the formation and evolution of planetary systems."

International Collaboration
The research was led by Subo Dong and Zexuan Wu of Peking University, with significant contributions from KASI researchers Ryu Yoon-hyun and Lee Chung-uk.

KMTNet’s ability to provide 24-hour continuous monitoring of the galactic center proved essential in capturing the brief microlensing event. Kang Kyung-in, Director of Space Science and Exploration at KASA, stated that the agency will continue to support joint observation projects between domestic ground telescopes and international space missions to further explore the mysteries of the cosmos.

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