Scientists say Earth may actually survive the Sun's death

Earth will probably survive the final stages of the Sun's evolution — the red giant phase and the subsequent asymptotic giant branch phase — but only if the Sun sheds its mass quickly enough during this period. That's the conclusion reached by an international team of scientists, whose findings were published in June in the journal Astronomy & Astrophysics.

The fate of Earth after the Sun's death has been debated in astronomy for decades: some studies predicted the star would swallow our planet whole, while others suggested Earth would make it out intact. The new study relies on an updated model of tidal interaction — the same effect behind the Moon-driven tides here on Earth.

A tug-of-war between gravity and mass loss

The researchers modelled how the orbits of Mercury, Venus, Earth and Mars would change as the Sun evolves into a red giant and later into an asymptotic giant branch star. Each planet's fate hinges on a battle between two opposing forces: on one hand, the expanding Sun intensifies tidal forces, dragging a planet's orbit inward; on the other, the Sun sheds mass as it evolves, weakening its gravitational pull and allowing the planet's orbit to widen instead.

"Earth's fate depends on a delicate balance between these two processes. If tidal forces win out, Earth gets swallowed. If mass loss wins, Earth drifts further away from the Sun," explained lead author Mats Esseldeurs, a researcher at the Institute of Astronomy at KU Leuven.

To pin down how quickly the Sun might lose mass at this stage, the team drew on data from the star L2 Puppis, which is currently going through precisely the same late-life phase the Sun will eventually reach, and which started out with a similar mass — 0.98 solar masses.

Mercury and Venus are doomed, but Mars stands a chance

According to the new model, neither Mercury nor Venus will make it through the red giant phase. Even though Venus's orbit would widen as the Sun expands, the Sun itself will grow faster than the planet can retreat. The same fate, the calculations suggest, awaits Mercury.

Mars, like Earth, has better odds simply because it sits farther from the Sun. According to the researchers' calculations, Mars should survive both the red giant phase and the subsequent asymptotic giant branch phase.

"The biggest uncertainty today isn't in the tidal interaction calculations anymore — it's in how much mass the future Sun will actually lose. Observations of Sun-like giant stars currently suggest Earth will survive, but we need more precise data to be fully certain," Esseldeurs concluded.

Source: novinky.cz