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Research Published On December 8, 2025 In The Astrophysical Journal Letters Shows That General Relativity Effects Can Destroy Up To 75% Of Exoplanets In Nearby Binary Systems, Helping To Explain The Observed Scarcity Of Twin-Sun Planets Among More Than 6,000 Confirmed Worlds
Among more than 6,000 confirmed exoplanets, only 14 orbit two stars simultaneously. The study on planets with dual stars, published on December 8, 2025, indicates that general relativity may destroy about 75% of these worlds in nearby binary systems.
Of the more than 4,500 stars known to host planets, almost all should form with planetary systems, and a large portion is born in pairs. Still, the so-called twin-sun planets remain rare in astronomical observations.
Astronomers have confirmed over 6,000 exoplanets, most of which were discovered by NASA’s Kepler Space Telescope and the Transiting Exoplanet Survey Satellite, TESS. Despite this volume, only 14 are confirmed to orbit binary stars.
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Based on current knowledge of planetary formation, scientists estimated that there should be hundreds of planets with two suns. The discrepancy raised the question of where the real equivalents of fictional worlds like Tatooine might be.
Astrophysicists from the University of California, Berkeley, and the American University of Beirut proposed an explanation based on Einstein’s theory of general relativity. The study was published in The Astrophysical Journal Letters.
How Orbital Precession Leads To Instability In Twin-Sun Planets
In most binary systems, the two stars have similar but not identical masses and orbit in elongated elliptical paths. A planet orbiting both experiences a variable gravitational force, causing a gradual shift in its orbit.
This movement is known as orbital precession, similar to the wobble of a spinning top. The stars themselves also undergo precession, but due to general relativity.
Over time, tidal forces bring the stars closer together. This approach accelerates the precession of the stars and reduces the rate of precession of the planet. When both rates equalize, a resonant interaction occurs.
At this point, the orbit of the planet stretches dramatically. It can drift far from the binary at one moment and dangerously approach at periapsis at another, initiating a process of orbital instability.
Resonance And The Disappearance Of Twin-Sun Planets
According to Mohammad Farhat, the first author of the study, two situations can occur. The planet may come too close to the binary system, suffering tidal disturbances or being engulfed by one of the stars.
Alternatively, its orbit may be so disturbed that it ends up ejected from the system. In both cases, the planet disappears.
Farhat emphasized that this does not mean that binary stars do not have planets. Only those that orbit at great distances can survive.
These distant worlds, however, are less likely to transit in front of their stars from Earth’s perspective, making detection by methods used by Kepler and TESS more challenging.
The Circumbinary Desert And The Observed Scarcity
Kepler identified about 3,000 eclipsing binary systems. Considering that approximately 10% of sun-like stars host large planets, it was expected that around 300 binary systems would also contain planets.
However, only 47 candidates were identified in these systems, with 14 confirmed. None of them orbit binary systems with periods shorter than seven days.
There is a general scarcity of circumbinary planets and a true desert around binaries with periods of seven days or less. Paradoxically, it is in these systems that planets expected to be detectable by transit are most likely to be found.
According to Farhat, binary systems are surrounded by zones of orbital instability where planets cannot survive. In these regions, complex gravitational interactions lead to the ejection or destruction of the planet.
Twelve of the 14 known planets orbit just beyond this unstable region. This suggests that they formed further out and later migrated inward.
General Relativity And Large-Scale Destruction
Using mathematical calculations and computational simulations, Farhat and Jihad Touma demonstrated that general relativity significantly alters the survival of circumbinary planets.
The results indicate that relativistic effects destroy about eight in ten planets that orbit nearby binary systems. Approximately 75% of these destroyed planets are completely eliminated.
Albert Einstein introduced general relativity in 1915, describing gravity as curvature of spacetime. A classic example is the extra precession of Mercury’s orbit, which Newton’s laws did not adequately explain.
The same physics applies to compact binary stars. Initially distant, they can come closer over tens of millions of years due to interactions with surrounding gas.
As they approach, tidal forces continue to shrink their orbits over billions of years. When the orbital period drops to about a week, relativistic precession becomes dominant.
Meanwhile, the planet’s precession slows down. When both rates equalize, resonance is established that deforms the planetary orbit.
Resonance, Ejection And Broader Implications
In resonance, the planet’s orbit becomes increasingly eccentric, precessing more rapidly while remaining synchronized with the shrinking orbit of the binary.
On this trajectory, it reaches the instability zone. The gravitational effects of three bodies come into play and clear the region.
According to the researchers, this mechanism eliminates planets without the need for additional external disturbances. It can remove multiple planets from compact binary systems.
The breakdown occurs relatively quickly, within a few tens of millions of years, within the billions of years lifespan of a star. Therefore, exoplanets around nearby binaries become rare.
Scientists are now applying their models to extreme environments, including star clusters orbiting supermassive black holes and binary pulsar systems.
These findings reinforce the ongoing importance of general relativity. The theory that explained Mercury’s orbit may also shed light on why planets with two suns are so uncommon in the observable universe.
The study titled “Apsidal Resonance Capture And The Demise Of Planets Around Spiral Binaries” was published on December 8, 2025, with DOI 10.3847/2041-8213/ae21d8.
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