A new scientific study is turning around one of astronomy's oldest doom predictions, the idea that Earth will eventually be swallowed whole by a dying sun. For years the dominant view among astrophysicists was that our planet had no real chance of escaping the sun's expansion into a red giant billions of years from now. A study published in the journal Astronomy and Astrophysics now challenges that conclusion, presenting fresh evidence that Earth could actually survive the sun's transformation rather than being consumed by it.
What is happening inside the sun right now
To understand why this question is even up for debate, it helps to look at what is actually happening inside the sun at this moment. The sun is currently in what scientists call its main sequence phase, a long stretch of stability that has already lasted about 4.5 billion years. During this phase the sun is powered mainly by the fusion of hydrogen into helium, a process that keeps it burning steadily without dramatic swings in size or brightness.
That stability will not last forever. Over the coming billions of years the sun will keep growing hotter and more luminous, even while it stays in this same basic phase. That slow rise in brightness alone is expected to become intense enough to boil away all of Earth's surface water, making the planet uninhabitable within the next two billion years, long before the sun even begins its dramatic transformation.
The red giant phase begins in about 5 billion years
Around 5 billion years from now, the sun's long stable phase will finally come to an end. By that point the hydrogen fuel in its core will be used up. The helium core left behind will start contracting under its own gravity, heating up in the process and igniting hydrogen fusion in a shell surrounding it. That shell burning will cause the sun's outer layers to swell up enormously while its surface temperature drops sharply, giving the star the deep red color associated with this stage of stellar evolution, known as the red giant phase. This is exactly where the uncertainty about Earth's fate begins.
Two forces pulling in opposite directions on Earth's orbit
As the sun balloons outward, two competing forces will fight over what happens to Earth's orbit. On one side, the sun will shed a large amount of its own mass through powerful stellar winds. As the sun loses mass, its gravitational pull on Earth weakens, and that alone would cause Earth's orbit to drift gradually outward, away from danger. On the other side, Earth's growing closeness to the sun's expanded gaseous envelope would create drag, and tidal forces, the difference in gravitational pull between the near and far sides of an object, would act like a brake, slowly stealing energy from Earth's orbit and pulling it inward.
Until now, most astrophysicists believed the tidal braking effect would win out over the outward push from mass loss. Under that scenario, Earth would keep losing orbital energy, spiral steadily closer to the swollen sun, and eventually get engulfed and vaporized inside it.
How the new study flips the calculation
The new study rebuilds that calculation using improved models of two things, how much mass the sun loses as it becomes a red giant, and how effective tidal dissipation really is at draining a planet's orbital energy. The researchers found that tidal dissipation, the mechanism that saps orbital energy and gradually turns elliptical orbits like Earth's into more circular ones, appears to be considerably weaker than earlier models assumed. That single change shifts the balance of the whole equation.
Supporting evidence comes from observations of a real red giant star called L2 Puppis, located roughly 209 light-years from Earth. Those observations suggest that a star like the sun could end up losing enough mass during its red giant transition for that mass loss effect to outweigh the pull of tidal forces. If that holds true for the sun, Earth's orbit would gradually widen instead of shrinking, dramatically improving its odds of surviving the red giant phase intact.
Why the fate of Earth is still far from settled
Even with this more hopeful outlook, nobody is calling Earth's survival a sure thing. Stellar winds behave unpredictably, and the thermal pulses that occur during the final, chaotic stages of a star's evolution involve too many variables to model with full precision. If it turns out the sun loses less mass than this new model predicts, tidal forces could still come out on top, dragging Earth inward toward eventual destruction anyway.
Mercury, Venus and Mars face very different outcomes
While Earth's own fate stays an open question, scientists are far more confident about what awaits the rest of the solar system. Mercury and Venus have no such uncertainty hanging over them, both worlds will be completely engulfed by the sun's expanding outer layers and destroyed forever under the combined force of extreme heat and tidal pull. Mars gets a somewhat gentler outcome, its permanent ice reserves will be vaporized by the sudden spike in temperature, but the red planet will actually migrate outward into a more distant orbit and escape physical destruction altogether.
New oceans could briefly appear on Jupiter and Saturn's moons
Farther out in the solar system, the effects turn strangely hopeful. Jupiter and Saturn will see the orbits of their moons reshaped by the changing conditions, and the surge in solar radiation could temporarily melt the icy crusts covering moons such as Europa and Enceladus, briefly creating oceans of liquid water on their surfaces. That means these distant, frozen moons could, at least for a while, take over as the solar system's new watery worlds, stepping into that role right around the time Earth itself turns into a scorched and lifeless husk.
