Although the earth beneath our feet feels solid and reassuring (most of the time), nothing in this universe lasts forever.
One day, our sun will die and push much of its mass out before its core shrinks into a white dwarf and gradually leaks heat until it is no more than a cold, dark, dead lump rock a thousand trillion years later.
But the rest of the solar system will be far away before then. According to new simulations, it will take only 100 billion years for any remaining planets to separate beyond the galaxy, leaving the dying sun far behind.
Astronomers and physicists have been trying to figure out the ultimate fate of the solar system for at least hundreds of years.
“Understanding the long-term dynamic stability of the solar system constitutes one of the oldest pursuits of astrophysics traced back to Newton himself, who speculated that mutual interaction between planets would ultimately drive the system unstable,”
But it is much more difficult than it may seem. The greater the number of organs involved in a dynamic system that interacts with each other, the more complicated the system grows and the more difficult it is to predict. This is called the N-body problem.
Due to this complexity, it is impossible to make deterministic predictions of the circuits of solar system objects past specific schedules. In addition to about five to ten million years, security flies right out the window.
But if we can figure out what will happen to our solar system, it will tell us something about how the universe can evolve on schedules far beyond its current age of 13.8 billion years.
In 1999, astronomers predicted that the solar system would slowly fall apart over a period of at least one billion billion — that is, 10 ^ 18 or a quintillion years. That was how long it would take, they calculated, for orbital resonances from Jupiter and Saturn to decouple Uranus.
However, according to Zink’s team, this calculation ruled out some important influences that could disrupt the solar system more quickly.
First, there is the sun.
In about 5 billion years, when it dies, the sun will swell to a red giant that swallows up mercury, Venus and Earth. Then it will push out almost half of its mass, blown away into space by star winds; the remaining white dwarf will be about only 54 percent of the current solar mass.
This mass loss will loosen the sun’s gravity on the remaining planets, Mars and the outer gas and ice giants, Jupiter, Saturn, Uranus and Neptune.
Second, when the solar system orbits the galactic center, other stars should come close enough to disrupt the orbits of the planets about once every 23 million years.
“By taking into account star mass loss and inflation of the outer planetary orbits, these encounters will become more influential,” the researchers wrote.
“With enough time, some of these flybys will come close enough to separate – or destabilize – the remaining planets.”
With these additional influences taken into account in their calculations, the team ran 10 N body simulations for the outer planets (omitting Mars to save on computational costs, as its influence should be negligible) using the powerful Shared Hoffman2 Cluster. These simulations were divided into two phases: up to the end of the solar mass loss and the phase that follows.
Although 10 simulations is not a strong statistical test, the team found that a similar scenario played out each time.
Once the sun has completed its evolution into a white dwarf, the outer planets have a larger orbit, but still remain relatively stable. However, Jupiter and Saturn are caught in a stable 5: 2 resonance – for every five times Jupiter orbits the Sun, Saturn orbits twice (the possible resonance has been suggested many times, not least by Isaac Newton himself).
These extended orbits, as well as the characteristics of the planetary resonance, make the system more susceptible to disturbances by passing stars.
After 30 billion years, such stellar perturbations link the stable orbits into chaotic ones, resulting in rapid planetary loss. All but one planet escape their orbits and escape into the galaxy as junk planets.
The last, lonely planet lasts for another 50 billion years, but its fate is sealed. Eventually, it is also knocked loose by the gravity of a passing star. In the end, 100 billion. Years after the sun has become a white dwarf, the solar system is no more.
It is a significantly shorter time frame than that proposed in 1999. And scientists carefully note that it depends on current observations of the local galactic environment and stellar flyby estimates, both of which may change. So it is by no means engraved in stone.
Although estimates of the timeline for the death of the solar system are changing, it is still many billions of years away. The probability that humanity survives long enough to see it is small.
The research is published in The Astronomical Journal.