January 23, 2021

Jupiter and Saturn will survive the Sun’s expansion, but will not make it out unscathed

As the Sun evolves, it will become a giant star

As the Sun evolves, it will become a giant star
Roen kelly

The Sun will evolve dramatically as it ages, increasing to a size that surrounds the orbits of Mercury, Venus and the Earth and losing almost half of its mass.

The outer planets will survive this projected 7 billion year evolution, but they will not escape unscathed: Since the gravitational pull of the Sun’s mass is what governs the orbits of the planets, the weight loss of our Sun will cause the outer planets to drift further apart, weakening their anchor to our solar system.

Numerical simulations of this likely outcome of our system led by Jon Zink of the University of California at Los Angeles have explored what happens to our outer planets after the Sun consumes the inner planets, loses half of their mass, and starts her new life as a white dwarf, reports the American Astronomical Society (AAS).

Zink and his collaborators show how giant planets will migrate outward in response to the loss of mass from the Sun, forming a stable configuration in which Jupiter and Saturn settle in a 5: 2 mean-motion resonance. Thus, Jupiter will orbit five times for every two orbits of Saturn.

But our solar system does not exist in isolation; there are other stars in the galaxy, and one passes near us approximately every 20 million years. Zink and his collaborators include the effects of these other stars in their simulations. They show that around 30 billion years from now, stellar flybys will have disturbed our outer planets enough to cause the stable configuration to become chaotic, rapidly throwing most of the giant planets out of the solar system.

The last planet standing will stay for a while longer. But in 100 billion years, even this last remaining planet will also be destabilized by stellar flybys and expelled from the solar system. After their eviction, the giant planets will independently roam the galaxy, joining the population of free-floating planets without hosts.

The combination of solar mass loss and stellar flybys will lead to the complete dissolution of the solar system, according to these simulations.


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