Measuring Rogue Planets via Microlensing

Measuring Rogue Planets Via Microlensing

January 4, 2026

Kamaraj IAS Academy

Prelims Plus

A January 2026 study in the journal Science detailed the direct mass measurement of a "Rogue Planet" using a rare cosmic alignment.

What is a Rogue Planet? A planet-sized body that does not orbit a star. These "nomads" are likely ejected from young solar systems due to gravitational chaos.
The Technique (Gravitational Microlensing): Based on Einstein’s General Relativity, the gravity of the rogue planet acts as a lens, magnifying the light of a distant background star.
The Breakthrough: By using the "Microlensing Parallax"—observing the event simultaneously from Earth and the Gaia Space Telescope—scientists measured the planet (KMT-2024-BLG-0792) to be roughly the mass of Saturn.
Scientific Value: Confirms that "starless" planets are common in the Milky Way and helps astronomers understand how planetary systems evolve and "lose" members.