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An illustration of a red giant star expelling its outer layers and losing mass as it nears the end of its life.(Image credit: JAXA)
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Earth might endure the sun’s fiery demise, even as our star engulfs the inner planets, according to a recent study employing advanced models.
The findings present a possible alternative outcome for our planet, which was previously believed to face certain destruction as the sun absorbs it in a thermonuclear blaze billions of years from now. As a yellow dwarf star, the sun is anticipated to have a stable, 10-billion-year lifespan. However, in approximately 5 billion years, it will exhaust the hydrogen fuel in its core and initiate hydrogen fusion in its surrounding shell. This process will cause it to expand dramatically into a red giant star, then an even larger “AGB star,” before eventually collapsing into a white dwarf.
Currently, in a Letter to the Editor published on June 19 in the journal Astronomy & Astrophysics, astronomers utilized stellar evolution models and observed a nearby dying star to re-evaluate Earth’s ultimate, potentially fiery fate.
Solar tug of war
As the sun enters its final life stages, Earth will be subjected to two opposing forces — a fate shared by innumerable worlds throughout the vast expanse of cosmic history.
As the sun inflates to potentially hundreds of times its present size, the augmented tidal forces will draw Earth towards our rapidly swelling, sputtering star. Yet, the surging sun will also eject its inflated outer layers into space via stellar wind. As it sheds a significant portion of its mass and becomes less massive, its gravitational pull will diminish, allowing our planet to drift outward into the solar system’s void, the models indicate.
“Earth’s destiny hinges on a delicate equilibrium between these two phenomena,” stated Mats Esseldeurs, a doctoral candidate at KU Leuven’s Institute of Astronomy in Belgium and the study’s lead author. “If tidal interactions prevail, Earth is consumed. If mass loss predominates, Earth is propelled to a wider orbit.”
Previous research has only complicated the issue. Studies have established different premises regarding solar mass loss, tidal forces, and planetary interactions that might occur as the inner solar system evolves. Consequently, it remains uncertain whether Earth will survive both of the sun’s giant phases before our star dwindles into a compact, dense stellar remnant known as a white dwarf.
In a ray of hope, astronomers have identified intact worlds orbiting white dwarfs. Conversely, some white dwarf systems are strewn with the rocky debris of their disintegrated planetary companions. Thus, the researchers observed the formerly sunlike, dying giant star L2 Puppis, situated 200 light-years away in the constellation Puppis, to gain insight into our solar future. L2 Puppis might be losing up to one-millionth of a solar mass annually, according to prior estimates, expelling a dusty disk believed to host a planet 12 to 16 times the mass of Jupiter.
A view of L2 Puppis, a dying star.
(Image credit: ESO)
Furthermore, the researchers conducted cutting-edge gravitational calculations “based on the internal structure and dynamics of evolved stars,” simulating the orbital progression of the inner solar system and the sun’s lifespan from its inception to its ultimate state as a “spent” white dwarf.
So long, Mercury and Venus
Drawing upon observations of L2 Puppis’ mass depletion, coupled with the refined stellar evolution models, the researchers forecasted that Earth will persist as it migrates to a position just beyond the expanding sun’s perimeter.
“The most significant uncertainty now stems not from tidal calculations, but from the extent of mass loss the future sun will undergo,” Esseldeurs commented in the statement. “Current observations of giant stars similar to the sun suggest Earth’s survival, but more precise observations are needed for definitive confirmation.”
A schematic illustration depicting the late stages of the sun, approximately 5 billion years from now, as it depletes the hydrogen supply in its core and expands to potentially hundreds of times its current magnitude. Simulations indicate Mercury and Venus will be engulfed, but Earth may find refuge in a safe orbit.
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However, even if Earth survives, our solar system companions will not be spared; the simulations suggest Mercury and Venus will be consumed by the infernal blaze of our fading star.
Further stellar observations and improved models will contribute to clarifying our planet’s fate. For instance, the European Space Agency’s PLATO mission, a space telescope designed to search for Earth-like planets around sunlike stars, is scheduled to launch next year. It is expected to detect planets orbiting aging stars, thereby providing a more precise account of this potentially imperiled population.
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