A "treacherous" star could eject Earth from the Solar System

A new astronomical study suggests that Earth might one day be ejected from the Solar System—not due to the Sun’s aging, but because of the unpredictable trajectory of a rogue star.

While such a scenario would unfold over billions of years, researchers are now modeling how significantly these cosmic intruders could destabilize planetary orbits—and the findings are far from reassuring.

How Stellar Flybys Disrupt Planetary Orbits

Traditionally, simulations of Solar System evolution have treated it as mostly isolated. However, the Milky Way is full of stars, some of which pass dangerously close to our cosmic neighborhood. These stellar flybys, though usually inconsequential, can profoundly impact the delicate gravitational balance keeping planets in place.

A new study published in the journal Icarus explores this possibility using 2,000 simulations run via NASA’s Horizons system—a highly accurate Solar System dynamics tool. By inserting flyby stars into these models, scientists found that such encounters could reduce the long-term stability of the Solar System by about 50%. This instability isn’t uniform—some planets are more vulnerable than others.

Mercury: The Solar System’s Silent Killer?

Of all the planets, Mercury stands out as the most unstable. Its orbit is already prone to increasing eccentricity, meaning it becomes more elliptical over time. This natural instability raises the chances of Mercury colliding with Venus or plunging into the Sun. The presence of a rogue star nearby only amplifies this risk.

Simulations show that Mercury is often lost in these scenarios—along with Mars, which also faces a relatively high risk of ejection. Even Pluto, though now classified as a dwarf planet, has a 3.9% chance of being flung out of the Solar System entirely. While Earth shows a lower degree of instability, its orbit becomes increasingly sensitive if another destabilized planet crashes into it or alters its trajectory.

Stellar Chaos vs. Internal Chaos: Which Is More Violent?

The study clearly distinguishes between two types of orbital instability: those generated internally within the Solar System and those caused by external stellar influences. According to the researchers, “the nature of star-induced instabilities is more violent than those arising internally.” In cases of stellar flybys, multiple planets are often lost—this outcome occurs roughly half the time. In contrast, internally generated chaos rarely results in such extreme planetary upheaval.

A surprising finding is that Earth’s risk of orbital instability from external stellar encounters is hundreds of times greater than previously thought—reshaping how scientists view the long-term stability of planetary systems.

A Clearer View of the Cosmic Neighborhood

Though these events are expected to unfold over the next five billion years, the study adds another layer of existential vulnerability to our cosmic perspective. Earth might not need to wait for the Sun to become a red giant to face its demise. A stray field star passing just a bit too close could be enough to fling our planet adrift into the cold, empty void of interstellar space.

“KORÇA BOOM”