Solar System's Life Expectancy Cut a Billion-Fold

New simulations show random solar mass-loss 'kicks' will destabilize the outer planets about a billion years after the Sun becomes a white dwarf.

A team led by Konstantin Batygin at Caltech ran hundreds of N-body simulations of the Sun, Jupiter, Saturn, Uranus and Neptune to see how the planets fare as the Sun dies. Earlier studies modeled the Sun shedding mass smoothly and found the giant planets' orbits, though doubling in size, would stay stable far longer than the age of the universe. The new work instead modeled mass loss as random, episodic ejections — "stochastic kicks" — and found the outer solar system disassembles roughly a billion years after the Sun becomes a white dwarf, according to AAS Nova's coverage of the study.

The reversal is dramatic: previous estimates gave the giant planets' orbits a quintillion-year lifespan, with break-up expected only from passing stars over 30–100 billion years. Euronews reports the new findings cut that expected stability a billion-fold, so the outer planets will be thrown into chaos roughly one billion years after the Sun becomes a white dwarf. As the team put it, Newton suspected the planetary order was mortal — and, per the researchers quoted by 404 Media, "Newton's envisioned instability is real after all. He was mistaken only about the perpetrator."

The simulations tied the outcome to each kick's ejection mass. AAS Nova reports that with very small ejection masses the dynamics mimic smooth mass loss; at intermediate values there is roughly a 20% chance Jupiter–Saturn and Uranus–Neptune enter mean-motion resonances; and for larger kicks of 10⁻⁵ solar masses or more, the outer system disassembles within billions of years. For the most realistic expected ejection mass of 10⁻⁴ solar masses, about 40% of simulations showed disruption or violent scattering during the red giant phase, and roughly 90% broke down within 3 billion years.

By the time any of this unfolds, the inner planets will already be gone: Earth, Venus and Mercury are expected to be consumed as the Sun swells into a red giant, with Mars surviving at a safer distance, Euronews reports. The study, "Terminal Instability of the Solar System Triggered by Stochastic Solar Mass Loss" in The Astrophysical Journal Letters, relocates the cause of the solar system's dissolution from passing stars or slow chaos to the Sun itself.

None of this is imminent: the Sun has around five billion years left before its red giant phase, and the outer planets' disassembly follows white dwarf formation by roughly a billion years. But the finding reshapes how astronomers model planetary systems around dying stars, suggesting stochastic mass loss — not smooth outflow — should be the default assumption.