Gravitational microlensing surveys have unveiled populations of free-floating planets. Although their masses haven’t been directly measured due to distance-related challenges, statistics suggest that many of these rogue planets possess less mass than Jupiter. Recently, astronomers identified a groundbreaking microlensing event, termed KMT-2024-BLG-0792/OGLE-2024-BLG-0516. This event involved an exoplanet with approximately 21.9% of Jupiter’s mass, situated 9,785 light-years (3,000 parsecs) from the Milky Way’s center.
An artist’s impression of a free-floating exoplanet. Image credit: Sci.News.
Traditionally, planets are linked to stars, but research indicates that many traverse the galaxy independently.
Known as free-floating or rogue planets, these celestial bodies lack stellar companions.
Due to their low light emissions, they are primarily detected through their gravitational influences, a technique known as microlensing.
A significant challenge of this discovery method is determining the distances to these planets, complicating mass measurements.
This has left much of the data regarding these solitary objects speculative.
In a recent study, Dr. Subo Dong from Peking University and the National Astronomical Observatory of Japan and collaborators discovered a new free-floating planet, KMT-2024-BLG-0792/OGLE-2024-BLG-0516, via a brief microlensing event.
In contrast to prior approaches, they utilized a novel strategy by observing the microlensing phenomenon concurrently from Earth and space, leveraging multiple ground-based surveys alongside ESA’s Gaia space telescope.
Variations in the timing of light captured by these different locations facilitated measurements of microlens parallax, enabling researchers to calculate the planet’s mass and position through finite source modeling.
“Based on comparisons with the statistical characteristics of other microlensing events and simulation predictions, we conclude that this object didn’t originate as an isolated entity (like a brown dwarf) but likely formed within a protoplanetary disk (like a planet),” the astronomers noted.
“Subsequent dynamic processes likely ejected it from its formation site, resulting in a free-floating object.”
For further details, check out the study published in this month’s Science: paper.
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Subo Dong et al. 2026. Microlensing of free-floating planets caused by heavy objects in Saturn’s vicinity. Science 391 (6780): 96-99; doi: 10.1126/science.adv9266
Source: www.sci.news
