Rare Circumbinary Exoplanets Explained by Einstein's Relativity

New research shows how the complex gravitational forces in tight binary star systems can destabilize and eject orbiting planets.

Published on Feb. 3, 2026

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A new study published in The Astrophysical Journal Letters has found that the scarcity of circumbinary exoplanets - planets that orbit two stars - can be explained by the effects of general relativity on the three-body interactions between the two stars and the planet. The researchers performed a mathematical analysis showing how the gradual shifting of the binary stars' orbits over millions of years can elongate a planet's orbit and ultimately lead to the planet being shredded by the stars or ejected from the system entirely.

Why it matters

Circumbinary exoplanets are a rare find, with only 14 confirmed to exist out of the over 6,000 exoplanets discovered so far. Understanding the reasons behind this scarcity is important for advancing our knowledge of planetary formation and evolution, especially in complex multi-star systems.

The details

The researchers studied how general relativity affects the orbits of tight binary star systems, where the stars gradually shift closer together over tens of millions of years. This causes the orbit of any planet in the system to become highly elongated, putting it at risk of either being destroyed by the stars or ejected from the system entirely due to the complex three-body gravitational effects.

  • The new study was published in The Astrophysical Journal Letters in February 2026.

The players

Mohammad Farhat

The lead author of the study and a postdoctoral researcher at the University of California, Berkeley.

Jihad Touma

A physicist at the American University of Beirut in Lebanon and a collaborator on the study.

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What they’re saying

“You have a scarcity of circumbinary planets in general, and you have an absolute desert around binaries with orbital periods of seven days or less.”

— Mohammad Farhat (University of California, Berkeley)

“And on the route, it encounters that instability zone around binaries, where three-body effects kick into place and gravitationally clear out the zone.”

— Jihad Touma, Physicist (American University of Beirut)

What’s next

The researchers are now wondering whether a similar approach could illuminate how relativistic effects influence other unexplained, extreme cosmic phenomena, such as the behavior of stars around binary supermassive black holes or pulsars.

The takeaway

This study provides an explanation for the scarcity of circumbinary exoplanets, showing how the complex gravitational forces in tight binary star systems can destabilize and eject orbiting planets over time. It highlights the power of general relativity to shed light on puzzling astrophysical phenomena.