For generations, scientists have believed they knew exactly how Earth would die. In roughly five billion years, after exhausting the hydrogen fuel at its core, the sun will swell into a giant red star and eventually expand so much that it engulfs the inner planets. According to most previous studies, Earth is expected to be among the casualties.

A new study, however, suggests the story may not be so straightforward. 

Using improved models of stellar tides and updated estimates of how much mass the aging sun could lose, researchers found that Earth might escape the sun’s final expansion instead of being swallowed by it. 

“Based on updated tidal dissipation prescriptions, Earth survives the RGB and AGB phases of the sun,” the study authors note.

However, arriving at that conclusion required revisiting one of the most uncertain aspects of the sun’s future evolution.

Why predicting Earth’s fate is tricky

The question—will Earth ultimately be engulfed by the dying sun, or can it survive by drifting into a wider orbit—has remained unresolved for years because two powerful forces compete as the sun ages. 

On one hand, the expanding star generates tidal interactions that can pull planets inward. On the other hand, the sun loses mass through stellar winds, weakening its gravitational grip and allowing planetary orbits to drift outward. 

Determining which effect dominates has proven difficult because both processes involve complex physics that scientists have struggled to model accurately. “The predicted fate of the Earth is highly sensitive to the tidal model and the assumed mass-loss rate,” the study authors note.

To investigate the problem, the study authors simulated the future evolution of the Solar System using modern stellar-evolution models. 

The team focused on what will happen after the sun leaves its current stable phase and enters two major expansion stages. The first is the red giant phase, during which the sun will dramatically increase in size after running out of hydrogen in its core. 

Later, after consuming its helium fuel, it will enter the asymptotic giant branch (AGB) phase, becoming even larger and shedding vast amounts of material into space.

At that point, two competing forces begin to determine the fate of the planets. As the sun expands, tidal interactions develop between the star and the planets orbiting it. These tides act like a brake, gradually draining orbital energy and pulling planets closer to the star. 

Previous studies generally concluded that this process would eventually drag Earth into the sun.

At the same time, however, the aging sun will lose enormous amounts of mass through stellar winds. As the star sheds material, its gravitational pull weakens, allowing planetary orbits to move farther outward. 

Predicting Earth’s future, therefore, comes down to determining which effect is stronger: the inward pull from tides or the outward push caused by mass loss.

A new look at the sun’s final years

The researchers revisited the problem using more sophisticated tidal models developed over the last fifteen years. These updated calculations suggest that giant stars dissipate tidal energy less efficiently than earlier estimates indicated. 

In simple terms, the future sun may be less effective at pulling Earth inward than scientists previously thought.

The team also examined how much mass the sun is likely to lose during its final evolutionary stages. To improve their estimates, they studied observations of L2 Puppis, a nearby aging star often described as a glimpse of the sun’s future. 

By analyzing this stellar analog, the researchers obtained updated constraints on how rapidly sun-like stars can shed material near the end of their lives.

When the researchers combined the revised tidal physics with modern mass-loss estimates, the balance shifted significantly. Their simulations showed that Earth’s orbit could expand enough to remain beyond the sun’s maximum size during both the red giant and AGB phases. 

Mars also survived in these scenarios, while the expanding star consistently engulfed Mercury and Venus. The findings suggest that weaker-than-expected tidal effects, coupled with substantial mass loss from the sun, could give Earth a chance to avoid the fiery fate predicted by many earlier studies.

However, this doesn’t mean life will also thrive on Earth after billions of years. Intense solar radiation at that time is likely to make the planet uninhabitable.

The hidden meaning behind these results

The study shows how improvements in stellar physics can reshape predictions of entire planetary systems. 

While astronomers have recently found evidence that aging stars can engulf nearby planets, the new research suggests Earth’s own fate may be less certain than previously believed. 

Instead of being doomed to spiral into the sun, our planet could survive if the sun loses enough mass during its final stages.

However, the researchers caution that the outcome remains uncertain. Their results depend heavily on how much mass the sun sheds during the asymptotic giant branch phase, a quantity that is still difficult to predict. 

“Currently, the survival of the Earth and the inner Solar System is not robustly determined and critically depends on the treatment of tidal dissipation and stellar mass loss,” the study authors said.

Future observations of evolved stars such as L2 Puppis and improved models of stellar tides could help narrow the uncertainty.

For now, the study does not guarantee Earth’s survival. Rather, it shows that one of astronomy’s most familiar predictions may need revisiting. 

The study is published in the journal Astronomy & Astrophysics.

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