Good news! Turns out the Earth will never be swallowed by the Sun

Some good news And some bad news. The good news is that, contrary to previous concerns, land It will probably never be swallowed The sun. The bad news, of course, is that none of us will be around to find out.

Scientists have long estimated that in about 5 billion years, the Sun will run out of fuel, expand first to become a red giant, and then eventually become a white dwarf that will continue to cool for tens — if not hundreds — of billions of years. Amid this dramatic sequence of cosmic events, the fate of Earth remains uncertain.

Will they be pulled into the expanding red sun and disappear forever? Or, even though it has long since become uninhabitable, will it continue to orbit the remains of the Sun’s white dwarf until the universe reaches final heat death?

Until now, the prevailing opinion among astrophysicists has been in favor of the first scenario. But a new study published in Astronomy and astrophysics It upends this prediction, providing new evidence that Earth may survive the Sun’s transformation into a red giant after all.

The life cycle of the sun

To understand what awaits the planets of the solar system, you have to look inside the sun itself. At present, the Sun is in the main sequence phase, a long period of stability lasting about 4.5 billion years, during which it is powered primarily by the fusion of hydrogen into helium.

This phase will continue for billions of years, but the Sun will gradually become hotter and brighter. Eventually, it will grow bright enough to vaporize all of Earth’s surface water, making our planet uninhabitable for the next two billion years.

About 5 billion years from now, the Sun’s long period of stability will end. By then, the hydrogen in its core will have been exhausted. The helium core will contract under its own gravity, heating it and stimulating hydrogen fusion in the surrounding shell. As a result, the Sun’s outer layers will expand enormously while its surface cools dramatically, giving it the characteristic red color of this stage of the star’s evolution. And here begins the mystery surrounding the fate of the Earth.

A complex tug of war game

The Sun’s massive expansion will profoundly reshape Earth’s orbit through the interaction of two opposing influences. On the one hand, the Sun will lose a significant amount of mass due to strong stellar winds. As its gravitational pull weakens, Earth’s orbit will gradually drift outward. On the other hand, the planet’s increasing proximity to the Sun’s expanding gaseous envelope would produce drag, while tidal forces—the difference in gravitational pull exerted on the near and far sides of the object, which can gradually change the planets’ orbits—would act as a brake on Earth’s motion.

Until now, scientists considered it highly likely that tidal effects were dominant. In this scenario, the Earth would gradually lose orbital energy, move inward, and eventually be swallowed by the expanding Sun, where it would evaporate completely.

New look

The new study, based on improved models of tidal dissipation and stellar mass loss as the Sun turns into a red giant, suggests a different conclusion. According to the researchers, tidal dissipation — the process that drains orbital energy and gradually causes elliptical orbits, like Earth’s, to become more circular — would be less effective than previous models suggested.

Meanwhile, the red giant notes L2 popswhich is located about 209 light-years from Earth, suggests that the Sun could lose enough mass for this effect to outweigh the effect of tidal forces. If so, Earth’s orbit would gradually move outward, greatly increasing its chances of surviving the red giant stage.

Uncertain future

Despite the study’s more optimistic outlook, Earth’s ultimate fate is still far from certain. The behavior of stellar winds and the complex thermal pulses that occur during the final stages of a star’s evolution involves many variables that are difficult to predict accurately. If the Sun eventually loses less mass than the new model estimates, tidal forces could take over, pulling the Earth inward and destroying it.

While Earth’s future remains an open question, the outlook for the rest of the solar system is clearer. As the Sun expands, Mercury and Venus will be swallowed whole by their outer layers, disappearing forever under the combined effects of intense heat and tidal forces. But exoplanets will follow a different path. Mars, although it would experience a significant temperature rise that would evaporate its permanent ice reserves, would migrate to a farther orbit and avoid physical destruction.

Further afield, the gas giants Jupiter and Saturn would see the orbits of their moons reshaped, while an increase in solar radiation could temporarily melt the ice crusts of moons like Europa and Enceladus, creating oceans of liquid water on their surfaces. Which means that these worlds – at least for a time – could become the successors to the Blue Planet after the Earth turned into a scorched wasteland.

This story originally appeared on Wired Italy It was translated from Italian.