The long-term stability of our solar system may be far more fragile than previously thought, according to a groundbreaking new study that was published in the journal Icarus. This is because passing stars have a subtle but significant impact.
While earlier simulations treated the solar system as an isolated system, researchers have now modeled thousands of scenarios where field stars (stars drifting through the galaxy) pass near our Sun over the next 5 billion years.
The results are startling. These stellar flybys could significantly alter the orbits of planets, increasing the risk of collisions or even ejections from the solar system.
The study found that the strongest stellar encounter in each simulation played a dominant role in shaping the outcome. Because the strength of such encounters is hard to predict, the potential impact varies widely, but in many cases, it’s dramatic.
The study suggests:
- Pluto, once considered stable, now shows a 5% chance of instability due to stellar encounters.
- Mercury’s risk of orbital disruption rises by 50–80%.
- There’s a 0.3% chance Mars could be lost through collision or ejection, and a 0.2% chance for Earth to suffer the same fate.
Astronomers may have just discovered our Sun’s long-lost sibling
These risks are significantly higher than those predicted by isolated models. The study also demonstrates that instabilities from passing stars are more likely to involve multiple planets and occur sooner, within the next 4 to 4.5 billion years.
The findings underscore the importance of considering the Sun’s galactic environment when predicting the future of our planetary neighborhood. As stars continue to drift through the Milky Way, their gravitational nudges may quietly reshape the fate of our solar system.
Authors noted, “Our simulations indicate that stellar passage effects typically scale with the impulse gradient of the most powerful stellar encounter that the solar system experiences, and they alter the future evolution of the solar system in a number of significant ways.”
Journal Reference:
- Nathan A. Kaib, Sean N. Raymond et al. The influence of passing field stars on the solar system’s dynamical future. Icarus. DOI: 10.1016/j.icarus.2025.116632