![An illustration shows how the Sun might look as it swells into a red-giant phase billions of years from now and moves closer to the inner planets. [NASA/JPL-Caltech/Lizbeth B. De La Torre]](/gc8/images/2026/07/14/56963-Sun-red-giant-370_237.webp)
An illustration shows how the Sun might look as it swells into a red-giant phase billions of years from now and moves closer to the inner planets. [NASA/JPL-Caltech/Lizbeth B. De La Torre] By BlueShift |
Roughly 5 billion years from now, when our Sun enters its red giant phase and its core heats up and contracts, its outer layers will expand enough to pull in and destroy nearby planets.
Scientists used to think that Earth would be among the planets doomed to spiral into our home star during this solar phase, and that it would melt into the Sun and become completely absorbed, alongside Mercury and Venus.
But a study published June 19 in the journal Astronomy and Astrophysics suggests this may not be the case.
Earth will survive the Sun's transition from its current and most stable phase to its red giant phase, the study's authors suggest -- though our planet's ultimate fate remains uncertain.
![This illustration tracks the life of a Sun-like star from its birth to its evolution into a red giant. It begins life as a protostar, and later becomes a star like our Sun. As its core begins to heat up, it expands and transforms into a red giant. After this, the star will push its outer layers into the surrounding space to form a planetary nebula, while the core of the star will cool into a dense remnant called a white dwarf. [ESO/M. Kornmesser via NASA]](/gc8/images/2026/07/14/56961-sun-stages-nasa-370_237.webp)
This illustration tracks the life of a Sun-like star from its birth to its evolution into a red giant. It begins life as a protostar, and later becomes a star like our Sun. As its core begins to heat up, it expands and transforms into a red giant. After this, the star will push its outer layers into the surrounding space to form a planetary nebula, while the core of the star will cool into a dense remnant called a white dwarf. [ESO/M. Kornmesser via NASA]
Our Sun began its life as a star-forming nebula -- a spinning cloud of molecular gas and dust. As gravity pulled this gas and dust together, causing the center to heat up and ignite, it evolved into a protostar.
The Sun is now around halfway through its main sequence phase, where it steadily converts hydrogen into helium in its core, generating the heat and pressure that prevent it from collapsing.
But that won't last forever.
Far into the future, after the Sun's core hydrogen is depleted, it will enter its red giant phase, followed by its horizontal branch and asymptotic giant branch (AGB) phases, when its core runs out of helium fuel and shuts down.
As helium and hydrogen fusion migrate to two distinct shells outside the dead carbon-oxygen core, the Sun will expand again.
Its outer layers will then drift away into space as a planetary nebula -- a glowing shell of gas and dust -- while its core will collapse into a white dwarf.
Over the course of billions of years, this dense, hot stellar remnant will gradually cool and dim.
Competing hypotheses
As the Sun moves from its current main sequence phase into its red dwarf phase and increases in size, gravitational forces will pull the Earth towards it, exacerbating the push and pull of the tides in our oceans.
The energy from these tides will slow Earth's rotation.
As the Sun expands and moves nearer to Earth, intense tidal waves will stir within the star. When they dissipate, it will pull Earth towards it.
Yet the growing Sun also will lose mass due to stellar wind, which pushes our planet further away.
"Earth's fate depends on a delicate balance between these two effects," the study's lead author Mats Esseldeurs, an astrophysicist at Belgium's University of Leuven, said in a statement.
"If tidal interactions predominate, Earth is engulfed by the Sun. If the Sun's mass loss predominates, Earth escapes into an orbit larger than the radius of its star," he said.
Until now, scientists had favored the first hypothesis.
But their calculations relied on relatively simple descriptions of tidal dissipation within giant stars.
Advances made in modeling these tides over the last 15 years have enabled the authors to show "the dissipation is lower than previously expected," astrophysicist Stephane Mathis of CEA Paris-Saclay in France, told AFP.
To estimate how much mass the Sun could lose, the team studied the nearby star L2 Puppis that is like the Sun's "old cousin," said Mathis, the study's co-author.
"A better understanding of tidal physics and the most advanced constraints we have on mass loss allow us to say that -- in the current state of knowledge -- Earth could move away from the Sun, contrary to what was predicted before," Mathis said.
Complex physics of aging stars
According to the new modeling, Earth will end up in a wider orbit around the white dwarf remnant that the Sun will eventually become.
Mars also escapes a death spiral into the Sun. But the two planets closest to the Sun, Mercury and Venus, will be swallowed by the expanding fireball.
"Given the current observational uncertainties in AGB mass-loss rates, the ultimate fate of the Earth remains uncertain, highlighting the need for improved constraints on the late-stages of stellar evolution," per the study's abstract.
"However, considering observational proxies for the Sun during the AGB phase, it is likely that the Earth will survive the Sun’s red giant phase."
In a summary of the study, KU Leuven's Institute of Astronomy said it shows how observations of evolved stars can provide clues about the distant future of our own Solar System.
"Although life on Earth will become impossible long before the Sun reaches its giant phases, the planet itself may endure," it said.
"Whether Earth ultimately survives or not, the answer lies in understanding the complex physics of aging stars, a problem astronomers are only now beginning to unravel."