Study says solar system lifespan is shorter than previously estimated

The lifespan of our solar system has been radically shortened by a new study showing the outer planets will be thrown into disorder a billion times earlier than expected. Published in The Astrophysical Journal Letters, the research calculates that the solar system will last only about one billion years after the Sun becomes a white dwarf, rather than the quintillion years previously estimated.

Terminal Instability Triggered by Stochastic Solar Mass Loss

For centuries, scientists including Isaac Newton assumed that the finely balanced gravitational pull between Jupiter and the Sun would eventually unravel the stability of the solar system, though modern computational work suggested both inner and outer planets were relatively safe. Yet, older simulations depended on the notion that the Sun would shed mass in a steady and uniform manner on its way to becoming a white dwarf roughly eight billion years from now. The new study, titled Terminal Instability of the Solar System Triggered by Stochastic Solar Mass Loss, reveals that dying stars actually eject mass randomly in both time and direction.

These random ejections generate velocity kicks that alter planetary dynamics. The authors write that the Sun in dying does not merely enlarge the planetary system it built, it shakes it, and more often than not, spills it. For very small ejection masses, dynamics mimic smooth mass loss, but intermediate values create a roughly 20 percent chance that Jupiter and Saturn, as well as Uranus and Neptune, enter mean-motion resonances. These resonant configurations do not protect the giant planets and actually disassemble slightly more often than nonresonant simulations.

Contrasting Timelines of Solar System Dissolution

While older theoretical models indicated the outermost planet Uranus would stay stable for a quintillion years, the new findings compress that timeline dramatically. The solar system will survive for a mere one billion years after white dwarf formation. Ejection models and observed kick amplitudes point to a future ejection mass of $10^{-4} text{ M}_odot$, which significantly increases the probability of orbit destabilization.

The research reveals a stark contrast in when this disruption might occur. While white dwarf cooling takes place roughly eight billion years from now, in 40 percent of the study’s simulations, planetary disruption and violent scattering occurred even earlier, while the Sun was still in its red giant phase.

Red Giant Expansion Threatens Planets Before White Dwarf Instability

The physical mechanism driving these disruptions involves both mass loss and orbital chaos. When the Sun becomes a white dwarf, it will rapidly cool and shrink down to almost half of its current mass while throwing out matter in random ejections. These ejections create kicks that alter the orbits of the outer planets.

Before the white dwarf phase is ever reached, the Sun will first turn into a red giant. This transformation will make all life extinct and potentially swallow our planet long before the white-dwarf instabilities occur. The authors of the study note that this timeline has no practical consequence for humanity, relocating the cause of dissolution away from passing stars or the slow seep of chaos and directly onto the dying Sun.