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Astronomers Successfully Weigh a Starless ‘Rogue Planet’ Drifting Through the Milky Way

Astronomers Successfully Weigh a Starless ‘Rogue Planet’ Drifting Through the Milky Way

Astronomers have measured the mass and distance of a rogue planet using gravitational microlensing observed from Earth and the Gaia spacecraft, offering rare insight into free-floating planets drifting through the Milky Way.

Written by Gadgets 360 Staff | Updated: 5 January 2026 21:39 IST

Astronomers Successfully Weigh a Starless ‘Rogue Planet’ Drifting Through the Milky Way

Photo Credit: Nature(2025)

Astronomers precisely measured a rogue planet’s mass using gravitational microlensing

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Highlights

Rogue planet weighed using Earth and space-based observations
Microlensing reveals mass of a starless Saturn-sized world
Microlensing reveals mass of a starless Saturn-sized world

Astronomers have weighed a starless "rogue" planet that is roaming the galaxy, an amazing discovery. Free-floating or rogue planets, which float in space alone, are hard to find. Scientists estimated the mass of the planet (~0.2 times Jupiter's, or about Saturn's) and its distance of 9,800 light-years by observing a gravitational lensing event from two observation points. A fresh vision of these mysterious domains has been unlocked by this breakthrough.

Weighing a Rogue Planet

In accordance with the recent study, the occurrence of microlensing, when a background star temporarily brightened because of the planet's gravitational pull, was detected by ground telescopes located in Chile, South Africa, and Australia. The emission was detected by the Gaia spacecraft, located about 1.5 million kilometers away by the European Space Agency, two hours later. This resulted in measuring the planet's distance. With this information, it was possible to determine its mass, estimated to be about 0.22 Jupiter masses or comparable to Saturn's, located at a distance of 9,800 light-years.

Astronomers Solve Mystery of Vanishing Planet

Rogue Planets: Origins and Future

Rogue planets may be more common than once thought — possibly even outnumbering stars in our galaxy. Most are believed to form in planetary systems and later get flung out by chaotic interactions. Only a few dozen have been detected by microlensing so far. But with this new technique and upcoming missions like NASA's Roman Space Telescope, many more of these wanderers are expected to be found.

Studying them promises insights into planet formation and the fate of planetary systems.Rogue planets may outnumber stars, forming in systems before being ejected. Few are detected so far, but new techniques and NASA's Roman Space Telescope could reveal many more, offering clues to planet formation and system evolution.

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Further reading: ESA, gravitational microlensing, Milky Way