The Solar System's retirement plan may need to be moved up. A new study finds that after the Sun dies, the outer planets' orbital lifetime is not the previously estimated 10^18 years (a billion billion) but roughly one billion years — the system's self-destruction could arrive 100 times faster than thought.
The research by Konstantin Batygin and Jim Fuller of Caltech and Fred Adams of the University of Michigan, "Terminal Instability of the Solar System Triggered by Stochastic Solar Mass Loss," was published in The Astrophysical Journal Letters (vol. 1009, 2026).
Decades of estimates rested on one assumption: that the Sun sheds nearly half its mass smoothly and steadily as it dies. Under that model, the outer planets' orbits would remain stable for 10^18 years — far longer than the age of the universe. Even accounting for passing stars' gravitational jostling, it would take 30 to 100 billion years to tear the system apart.
The new study changes one small thing with enormous consequences: the Sun ejects material in random, stochastic bursts, in random directions and at random times. Each burst gives the planets a small kick. Enough kicks accumulate to knock Jupiter and Saturn off their orbits.
The team's numerical simulations show that within three billion years after the Sun becomes a white dwarf, the Solar System self-destructs in 90% of models, with at least one giant planet hurled into interstellar space.
"We lose them. In nine out of ten of our simulations, at least one giant planet is hurled into interstellar space," Batygin told ScienceAlert. That dovetails with microlensing surveys suggesting there may be as many free-floating planets in the galaxy as there are stars — and dying suns are plausibly a major source.
Notably, in 40% of the simulations the planets didn't even survive to the white dwarf stage: they were scattered while the Sun was still a red giant.
"Newton's envisioned instability is real after all," the researchers write. "He was mistaken only about the perpetrator." Newton once worried that the gravitational interplay between Jupiter and Saturn would unravel the Solar System; later computations largely dismissed the concern. The new work says the real culprit is not gravitational tugging but the Sun itself.
The simulations produced some curiosities: sometimes Jupiter and Saturn get locked in a 5:2 orbital resonance (five Jupiter laps for every two of Saturn), and Uranus and Neptune in a 2:1, with roughly a one-in-six to one-in-five chance. But resonance offers no shelter — captured systems survive somewhat less often.
To be clear: this has nothing to do with humanity's future. The Sun is 4.57 billion years old and will burn for roughly five billion more years before expanding into a red giant, then shrinking into a white dwarf holding a little over half its current mass. The "accelerated breakup" happens billions of years after that.
But the theoretical implications are significant. "Ninety-seven percent of stars die this way, and many of the systems out there are more fragile than ours," Batygin said. "The quiet retirement we imagined for planetary systems is a myth."
Nature featured the work as a research highlight on October 6. The inner planets, meanwhile, had their verdict long ago: Mercury's orbit has about a 1% chance of going haywire before the Sun leaves its main-sequence phase. The outer planets were supposed to be the safe part — now that safe zone is gone too.