What will happen to the planets when the Sun dies

In about 5 billion years, the Sun will turn into a red giant and eventually become a white dwarf star. According to a new study by scientists, this process could destabilize the orbits of the planets in the Solar System, causing some of them to be ejected from the system. This was reported by Naked Science, citing a study published in The Astrophysical Journal Letters.

According to scientists' calculations, when the Sun becomes a red giant, its outer layers could reach the current orbit of the Earth. However, Earth's exact fate remains unknown: the planet might shift to a farther orbit or approach the star as a result of interaction with the Sun's atmosphere.

Then, the Sun will shed its outer layers and turn into a white dwarf. In the new study, scientists took into account that its mass decreases not uniformly, but through periodic pulsations. These changes can affect planetary orbits and, over time, disrupt the stability of the entire system.

According to the modeling results, within the first 3 billion years after the Sun becomes a white dwarf, orbital stability was disrupted in 96 percent of the modeled planetary systems. In 40 percent of the systems, instability began even while the Sun was still in the red giant phase.

This does not mean that all planets will necessarily perish. In some scenarios, the orbits of Uranus and Neptune could swap places, while other planets might be knocked out of their orbits. It is also possible that some systems will maintain their stability for a long time.

The authors of the study estimate the average lifespan of systems similar to the Solar System in realistic models to be about 1 billion years. In idealized calculations assuming the Sun's mass decreases uniformly, this period reached up to a quintillion years. However, such a scenario does not fully reflect the actual evolution of the star.

Scientists emphasize that the new results do not answer all questions about the future of the Solar System. The discovery of planets around white dwarfs and even neutron stars shows the need for a deeper study of how they manage to survive stellar evolution.