For decades, the fate of our Earth has been regarded as one of astronomy’s major doomsday scenarios. As the Sun reaches the end of its fuel supply far in the future, it will expand into a Red Giant, significantly altering the inner solar system. However, recent calculations present a less definitive outcome. Our planet may survive the late giant phases of the Sun, although it would no longer be a hospitable place.
The Earth May Escape the Sun
A research team led by Mats Esseldeurs from KU Leuven has re-modeled the Earth’s development during the later life phases of the Sun. The study, published in Astronomy & Astrophysics, reveals the surprising conclusion that the Earth might survive both the Red Giant phase and the subsequent Asymptotic Giant Branch (AGB) phase, which is the Sun’s final significant development stage. In contrast, Mercury and Venus would stand no chance and would be engulfed by the bloated star.
A Cosmic Tug of War
The outcome hinges on a cosmic tug of war. On one hand, the Sun expands so greatly that tidal forces could pull the Earth inward. On the other hand, the aging Sun loses substantial mass through stellar winds, weakening its gravitational pull, allowing Earth’s orbit to move outward. Esseldeurs summarizes, “If tidal interactions dominate, the Earth will be swallowed. If mass loss prevails, the Earth escapes to a more distant orbit.”
Older Models Painted Darker Pictures
Earlier calculations reached different conclusions as they operated on previous assumptions about tidal friction within aging stars. According to these older models, Earth would survive the Sun’s initial giant phase, but would eventually spiral into the Sun during the AGB phase. The recent work utilizes updated ab-initio models (calculation and simulation methods based on fundamental physical principles) for tidal interactions, resulting in a weaker inward movement of Earth.
Uncertainties in the Future
Still, the salvation of Earth isn’t certain. Researchers underscore that our planet’s future significantly depends on how rapidly the Sun sheds mass in its declining stages. At lower mass loss rates, the Sun might still ensnare the Earth. Conversely, higher rates could allow our planet to distance itself sufficiently to avoid being engulfed. The loss dynamics during the AGB phase remain particularly uncertain.
A Star as a Glimpse into the Future
As a comparative object, researchers examined L2 Puppis, an aging star that closely approximates the Sun’s original mass. Observations suggest that a similar mass in the AGB phase could lose enough mass that Earth could veer outward instead of colliding with the star. However, varied measurement techniques yield inconsistent results for L2 Puppis, highlighting the uncertainty of projections.
Earth’s Terminal Conditions
According to the study, even if the Earth survives the Sun’s expansion, it would not be a happy ending. Long before the giant phase starts, the rising luminosity of the Sun would drastically deteriorate conditions on Earth. Oceans and atmosphere could vanish or become uninhabitable much earlier on. Thus, the new investigation doesn’t answer whether life will continue on Earth but clarifies whether the planet, as a celestial body, can physically survive.
The Sun Ends as a White Dwarf
Ultimately, the Sun will shed its outer layers and shrink down to a white dwarf. If the Earth remains unconsumed by then, it would orbit the stellar remnant in a more stable trajectory. Models suggest Mars may also survive, while Mercury and Venus will be lost during the Red Giant phase. The NASA describes Earth’s fate in such scenarios as less certain than that of the inner planets.
Researchers view their calculations as a new constraint on an enduring problem rather than a definitive answer. Future observations of aging stars and missions like PLATO may enhance our understanding of how planets react during the late phases of their stars. Until then, Earth’s end remains open-ended: It may be swallowed by the Sun or, as a burnt-out planet, outlive its star.
Sources: “The fate of Earth during the Sun’s giant phases” (Astronomy & Astrophysics, 2026), Institute for Astronomy at KU Leuven, NASA, Experimental Astronomy.
