Einstein's Theory Reveals Why Two-Sun Planets Vanish

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Astronomers have long wondered why planets orbiting two stars, like the fictional Tatooine in Star Wars, are so incredibly rare. New research from UC Berkeley indicates the answer lies in Einstein's general theory of relativity, which explains how gravity subtly reshapes orbits over millions of years, ultimately destabilizing those of planets in binary star systems and causing them to be flung out or destroyed.

Why it matters

This discovery highlights the importance of considering relativistic effects when searching for exoplanets, particularly those in binary star systems. Future exoplanet missions will need to account for these subtle gravitational influences to accurately assess the prevalence of circumbinary planets.

The details

Binary stars frequently orbit each other closely, creating complex gravitational interactions. A planet orbiting both stars experiences a constantly shifting gravitational pull, causing its orbit to slowly rotate - a process called orbital precession. Over time, tidal forces draw the stars closer together, accelerating their orbital precession whereas simultaneously slowing the planet's precession. When these rates align, the planet's orbit becomes stretched, swinging it dangerously close to the stars or far away from them, leading to its ejection or destruction.

• For years, astronomers have pondered this cosmic puzzle.
• NASA's Kepler and TESS missions anticipated discovering hundreds of planets around tight binary systems, but only 14 confirmed circumbinary planets have been identified.

What they’re saying

What’s next

Advancements in computational modeling will allow astronomers to simulate the long-term evolution of planetary orbits in binary systems with greater precision, helping to predict which planets are likely to survive and where they might be found.