Full Breakdown
New Study Suggests Earth May Survive Sun’s Red-Giant Phase
6/29/2026, 11:25:39 AM
Earth’s Potential Escape from the Sun’s Red-Giant Expansion
In about five billion years the Sun will exhaust core hydrogen, swell into a red giant, and potentially engulf the inner planets. New modeling by KU Leuven and CEA Paris-Saclay shows Earth could avoid engulfment if solar mass loss outweighs tidal drag, allowing its orbit to expand beyond the star’s radius.
Red-Giant Evolution and Competing Forces
As a Sun-like star expands, stellar winds shed mass, weakening gravity and letting planets drift outward. At the same time, tidal forces raised in the star’s envelope act as a brake, pulling close planets inward. The net outcome depends on which effect dominates.
Study Team and Observational Basis
The study was led by Mats Esseldeurs, a doctoral candidate at KU Leuven’s Institute of Astronomy, with collaborators at CEA Paris-Saclay. Models were calibrated using observations of L2 Puppis, a dying giant 200 light-years away that loses up to 10?6 M? yr?¹. The ESA PLATO mission, launching next year, will provide comparable data.
Main Findings
The Sun will become a red giant in ~5 billion years; L2 Puppis suggests mass loss up to 10?6 M? yr?¹; revised tidal calculations show weaker drag; Mercury and Venus are expected to be engulfed, Earth may shift to an orbit just beyond the Sun’s radius, and Mars, at twice Earth’s distance, likely survives.
Significance for Planetary Futures
If Earth’s orbit expands, surface temperatures will still rise beyond habitability, ending life as we know it. Nonetheless, the possibility of orbital survival revises expectations for planetary system stability and guides searches for planets around white dwarfs and other evolved stars.
Official Summary
Esseldeurs said Earth’s fate hinges on the balance between tidal drag and mass loss, noting earlier models overestimated tidal braking. KU Leuven’s press release called for better observations of Sun-like giants to refine predictions.
Prior Models and Counterpoints
Earlier studies, assuming stronger tidal dissipation, concluded Earth would be inevitably engulfed. The new work challenges that view by showing tidal energy loss inside giant stars is less efficient.
Remaining Uncertainties
The main gaps are (1) the exact amount of solar mass loss during the asymptotic-giant-branch phase and (2) the efficiency of tidal dissipation in expanded envelopes. L2 Puppis observations guide models but remain insufficient for definitive forecasts.
Verbatim Quotes
- “The fate of Earth depends on a delicate balance between these two effects,” — Mats Esseldeurs, KU Leuven Institute of Astronomy
- “If tidal interactions dominate, Earth is engulfed. If mass loss dominates, Earth escapes to a wider orbit.” — Mats Esseldeurs, KU Leuven
- “The largest uncertainty no longer comes from the tidal calculations, but from how much mass the future sun will lose,” — Mats Esseldeurs, KU Leuven
- “Observations of sun-like giant stars currently point towards Earth's survival, but we need better observations before we can be certain.” — Mats Esseldeurs, KU Leuven
Future Work
High-resolution monitoring of L2 Puppis and PLATO data will refine mass-loss rates and tidal models, clarifying Earth’s long-term orbital fate and informing the search for planets around evolved stars.
