New Models Suggest Earth Could Escape Sun's Red Giant Phase
Astronomers using updated stellar evolution models say Earth may avoid being engulfed by the Sun as it expands, though Mercury and Venus are likely to be consumed.
Astronomers have applied recent stellar evolution models and observations of a nearby dying star to reassess the long-term fate of Earth. Their calculations, published in a June 19 letter to Astronomy & Astrophysics, indicate that as the Sun exhausts its core hydrogen in about five billion years and expands into a red giant, the planet could be pulled outward by the Sun’s decreasing mass, potentially moving it beyond the star’s swollen radius.
"The fate of Earth depends on a delicate balance between these two effects," said Mats Esseldeurs, a doctoral candidate at KU Leuven’s Institute of Astronomy and lead author of the study. "If tidal interactions dominate, Earth is engulfed. If mass loss dominates, Earth escapes to a wider orbit."
The research incorporated gravitational calculations based on the internal structure of evolved stars and used data from the dying giant L2 Puppis, located roughly 200 light-years away, which is shedding mass at an estimated rate of one-millionth of a solar mass per year. By combining these observations with the updated models, the team projected that Earth would likely survive by shifting to an orbit just outside the Sun’s expanded envelope, while Mercury and Venus are expected to be consumed.
Esseldeurs noted that the primary uncertainty now lies in the amount of mass the Sun will lose during its giant phases. He added that further observations of Sun-like giant stars are needed to refine the prediction. Future missions such as the European Space Agency’s PLATO telescope, slated for launch next year, may provide additional data on planets orbiting aging stars, helping to clarify the long-term prospects for Earth and similar worlds.
