Will Earth Survive the Sun’s Final Expansion?
Earth may avoid being swallowed by the sun when it enters its red giant phase in approximately 5 billion years, according to research published in the journal Astronomy & Astrophysics. While older models suggested our planet would be engulfed, updated calculations indicate that the sun’s loss of mass will weaken its gravitational grip, allowing Earth to drift into a wider, safer orbit.
How Does the Sun’s Evolution Threaten Earth?
The sun’s transformation into a red giant creates a “cosmic tug-of-war” between two opposing forces: tidal forces and mass loss. As the sun expands, its gravitational tides act as a brake, draining Earth’s orbital energy and pulling the planet inward. Simultaneously, the star sheds vast amounts of gas, eventually losing about half its mass. According to NASA, as the star becomes lighter, its gravitational hold on surrounding planets weakens, pushing them outward. Lead author Mats Esseldeurs of the KU Leuven Institute of Astronomy states that the planet’s fate hinges on which of these two effects dominates. If tidal interactions dominate, Earth is engulfed; if mass loss dominates, the planet survives.
Astronomers use red giant stars like L2 Pup—located roughly 183 light-years away—as proxies to study how our sun might behave in the future. By observing L2 Pup’s mass-loss rates, researchers have found evidence that Earth may indeed drift outward just quickly enough to escape destruction.
Why Do Recent Findings Differ from Older Models?
Previous studies often predicted Earth’s demise because early models relied on simplified prescriptions developed decades ago or ignored tidal interactions altogether. The team at KU Leuven updated these calculations by accounting for the complex internal structure and dynamics of aging stars. By testing these new formulas against a range of mass-loss scenarios, researchers concluded that while Mercury and Venus will inevitably be consumed, Earth and Mars are likely to migrate to broader orbits, eventually circling the white dwarf remnant that the sun will leave behind.
Is Earth Guaranteed to Survive?
Despite these findings, the ultimate fate of the planet remains uncertain. Mats Esseldeurs notes that the largest uncertainty is no longer tidal calculations, but rather the precise rate at which the future sun will lose its mass. Current observations of sun-like giants point toward survival, but astronomers require better observations to confirm this outcome. Furthermore, even if the planet physically survives the sun’s expansion, it will not necessarily be hospitable. Most scientists agree that the sun will grow steadily hotter, boiling Earth’s oceans and rendering the planet completely uninhabitable in about 1 billion years, long before the sun begins to expand.
Frequently Asked Questions
Will Earth be destroyed when the sun becomes a red giant?
Not necessarily. While previous studies suggested engulfment was inevitable, new research indicates that the sun’s mass loss may push Earth into a wider, safer orbit, allowing the planet to survive.
What happens to Mercury and Venus?
According to the study, Mercury and Venus are unable to outpace the sun’s expansion and will be inevitably engulfed.
Could humans survive the sun’s expansion?
Likely not. Scientists estimate that the sun will grow hotter in about 1 billion years, causing Earth’s oceans to boil and making the planet uninhabitable long before the sun begins to expand.
Why is mass loss important?
As a star loses mass, its gravitational pull on orbiting planets weakens. This allows planets to drift into wider orbits, which can act as a buffer against the star’s physical expansion.
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