If you think the end of the world is something that only happens in Hollywood movies, you might want to think again. A new study by astronomers from the Institute for Planetary Sciences in the U.S. and the University of Bordeaux in France reveals: A rogue star, one not belonging to our solar system, could tilt the orbits of planets and disrupt the entire cosmic order. The result? Earth could crash into another planet, fall into the sun, or be ejected from the solar system into interstellar space – a cold, dark realm with no source of heat, light, or life.
The good news: It's probably not happening anytime soon. The bad news? The chance of it happening within the next 5 billion years is higher than previously thought.
According to simulations by researchers Nathan Kaib and Sean Raymond, published on arXiv, the main culprit behind this potential chaos is Mercury. The elliptical orbit of the small, innermost planet is heavily influenced by the massive gravitational pull of Jupiter. In certain situations – especially if an external star passes near the solar system – Mercury’s orbit could become extreme and unstable.
What happens then? Mercury crashes into Venus or the sun, triggering gravitational chaos. As a result, Venus or Mars could veer off course, strike Earth, or hurl it toward Jupiter – ultimately causing the ejection of our home planet from the solar system. In other words: Instead of light, warmth, and life – absolute cold and interstellar isolation.
Only a 0.2% Chance? That's a Lot
Granted, the researchers clarify that "the chance is very low," as Kaib casually put it – "only 0.2% over five billion years." But that's still several times higher than previous studies, which ignored the long-term effects of passing stars.
“How little we know about the impact of this possible planetary chaos. It’s a little frightening,” admitted Dr. Renu Malhotra of the University of Arizona, who was not involved in the study. According to her, it's possible that rogue stars have already disrupted the solar system in the past – and that may be why the orbits of the giant planets are elliptical rather than perfectly circular, as expected when they first formed.
Pluto Might Survive (Or Not)
Surprisingly, the dwarf planet Pluto is considered relatively stable – thanks to a “3:2 resonance” with Neptune: For every three orbits Neptune makes around the sun, Pluto makes two. What does this mean? When Pluto reaches its closest point to the sun, Neptune is always far away. In fact, Pluto comes closer to Uranus than to Neptune.
But it’s a delicate situation. “If external stars shake the solar system, Pluto might be pushed out of this resonance,” explains Kaib. Then – it could either be destroyed in a collision or flung far into space. The chance of that happening within 5 billion years: About 4%. That’s 20 times the risk to Earth.
These Are the Stars to Worry About
The most dangerous stars are those that pass within less than 100 astronomical units (AU) – that is, less than 100 times the distance between the Earth and the sun. The likelihood of such an encounter over 5 billion years? Around 5%. Additionally, the slower a rogue star moves (less than 10 km per second), the longer its gravitational influence lasts – and the more destructive it may be.
Here’s how the researchers summed up the finding: “Encounters with rogue stars could significantly affect the dynamic stability of the planets – and the overall architecture of the solar system.”
But these aren’t just theoretical scenarios. Scientists have already identified a concrete candidate that might destabilize the cosmic order: The star Gliese 710, an orange dwarf from a neighboring system, is expected to pass near our solar system in about 1.3 million years. According to forecasts, it could approach as close as 10,000 astronomical units – precisely the threshold at which dangerous gravitational effects begin. While a collision is not expected, its gravity could deflect comets, disrupt the Oort cloud, and potentially even shake the stability of planetary orbits. In short, real threats don’t always come in the form of a giant asteroid – sometimes, they show up as an innocent-looking star just passing through the neighborhood.
And Maybe It Will Settle One Old Debate
If such a scenario comes to pass, the researchers say with a mix of humor and seriousness, at least one question will finally be resolved – the debate over Pluto: Is it a planet or not? If it’s completely wiped out from the solar system, the question becomes irrelevant. Only if that day does come, there’s little chance anyone will be left to argue about Pluto’s astronomical classification.