Scientists Discover How to Build a Habitable Planetary System That Could Last Forever

How multiple planetary horseshoe orbits might evolve over time. Credit: Raymond et al

In a groundbreaking study recently published in Monthly Notices of the Royal Astronomical Society, scientists have delved into the possibility of creating planetary systems that could last forever. Imagine a future where interstellar travel becomes as effortless as a walk in the park, where vacationers in a galactic empire can explore a multitude of worlds without the hassle of traversing vast distances. This captivating concept revolves around the idea of compacting numerous planets within the habitable zone of a single star—a concept that may redefine our understanding of habitability and open doors to the existence of advanced civilizations.

One of the primary challenges of habitable zones is their limited range. In our own solar system, the planets Venus and Mars, despite their potential for habitability, reside outside the sun's habitable zone. A hypothetical super-advanced species might consider adjusting the orbits of these planets to bring them closer to Earth. However, such alterations could introduce unforeseen complications. If the orbits of neighboring planets become too similar, gravitational disturbances over extended periods could render all three orbits unstable, thus undermining the purpose of re-engineering our system.

Fortunately, there exists a captivating solution: the concept of mutual horseshoe orbits. This phenomenon is observed in Saturn's moons Epimetheus and Janus. As they share an orbit, one moon gradually gains speed until it almost catches up with the other, initiating a mesmerizing gravitational dance. The outer moon is pulled inward, while the inner moon is pushed outward, ensuring that the two moons never collide. These horseshoe orbits enable multiple celestial bodies to occupy similar orbital paths without destabilizing the system.

Drawing inspiration from this natural occurrence, scientists explored the possibility of creating mutual horseshoe orbits between two Earth-like worlds orbiting a sun-like star within the habitable zone. While capturing small bodies into horseshoe orbits with Earth has been observed, such configurations tend to be unstable. However, when the masses of the bodies are similar, the orbits become significantly more stable.

To determine the potential of such systems, the research team assumed Earth-mass planets orbiting at 1 au from a sun-like star. Their findings revealed that it is feasible to pack up to 24 Earth-like worlds into stable horseshoe resonances. Under the right conditions, these orbits could remain stable for billions of years, providing an unprecedented opportunity for long-lasting planetary systems.

Taking their investigations even further, the researchers explored how such a system might appear from afar. If the aligned orbits of these planets were to periodically pass in front of their star as viewed from a distant vantage point, they could be detected as exoplanets using the transit method—an exciting prospect that could serve as evidence of an advanced civilization.

Although the chances of discovering such an extraordinary system are slim, the mere contemplation of its existence ignites the imagination. Envision a night sky adorned with Earth-like worlds, 23 in addition to our own—a sight so spectacular that it would undoubtedly entice individuals to seek out dark-sky locations to marvel at its splendor.

While the creation of such intricate planetary systems remains purely speculative, this study showcases the innovative thinking and boundless curiosity of scientists as they strive to uncover the mysteries of the universe. As our understanding of celestial mechanics and habitability evolves, perhaps one day we will witness the birth of a civilization capable of engineering such celestial marvels, leading to a future where endless exploration awaits us among the stars.

Journal Information: Sean N Raymond et al, Constellations of co-orbital planets: horseshoe dynamics, long-term stability, transit timing variations, and potential as SETI beacons, Monthly Notices of the Royal Astronomical Society (2023). DOI: 10.1093/mnras/stad643