What is the fate of Mercury and Venus when the Sun expands into a Red Giant?
Answer
They will likely be engulfed by the swollen solar radius
During the phase immediately following core helium ignition, the Sun swells dramatically, transforming into a Red Giant. This expansion causes the stellar radius to increase enormously. Calculations based on stellar modeling predict that this expansion will be so great that it will encompass the orbits of the innermost planets. Specifically, Mercury and Venus are projected to be swallowed whole by the star's vastly inflated outer layers. The fate of Earth remains uncertain but is predicted to be either engulfed or baked into a sterile cinder by the intense radiation.
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