Simulations show risk of giant planets colliding due to the Sun’s mass loss — Live Science

New computer modeling suggests that Jupiter, Saturn, Uranus and Neptune may lose their stable orbits and collide with one another because of the Sun’s uneven loss of mass. As Live Science reports, in some scenarios, instability may develop during the red giant phase or over several billion years after it.

In about five billion years, the Sun will exhaust the hydrogen in its core, expand into a red giant and eventually become a white dwarf. It was previously believed that the four giant planets would largely survive this process: the Sun’s mass loss was expected to push their orbits farther from the star and keep the system stable for hundreds of billions of years.

Uneven mass loss

The new calculations consider a scenario in which the Sun sheds its outer layers not smoothly but in large clumps of plasma. Each such ejection may give the star a small impulse, similar to recoil. The combined impulses could alter the Sun’s motion and disrupt its gravitational influence on the outer planets.

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The study’s authors examined three scenarios: smooth mass loss, clump ejections throughout the red giant phase, and their occurrence only at the final stages. They also varied the mass of the ejected clumps.

Results of 672 simulations

In the smooth mass-loss scenario, the outer part of the Solar System retained nearly all its main features, as in previous studies. In contrast, models with uneven ejections showed chaotic evolution: the planets could swap places, move onto elongated orbits, or leave the Solar System altogether.

In 96% of simulations involving the most massive packets of ejected matter, the giant planets eventually collided. In extreme scenarios, instability emerged during the red giant phase, while in others it occurred in less than several hundred million years after the Sun became a white dwarf. The results could change perceptions of the stability of planetary systems around white dwarfs.