Without an extraordinarily powerful magnetic field for protection, no life could endure a star's final stages before it becomes a white dwarf, according to recent research from the University of Warwick. Any life detected on planets orbiting these stellar remnants likely originated after the star's death.
Every second, charged particles from the solar wind bombard Earth. Our planet's magnetic field deflects most of them, creating life-friendly surface conditions. However, this shield is temporary. As the Sun nears its end, new research shows it will fail to protect us.
In about five billion years, the Sun will deplete its core hydrogen, causing the core to contract under gravity while the outer layers expand dramatically. The Sun will swell enormously, evolving into a red giant.
During expansion, its atmosphere may engulf Mercury and Venus, and possibly Earth. After roughly a billion years, the Sun will shed its outer layers and collapse into a white dwarf, cooling over billions of years before fading entirely.
In a study by University of Warwick astronomers, researchers modeled stellar winds from 11 stars (1-7 solar masses) to assess how wind intensity changes over five billion years as stars become red giants. They also evaluated if planetary magnetospheres could survive.
The models reveal that as stars expand toward their end, stellar wind speed and density fluctuate wildly, compressing and expanding planetary magnetic fields until they collapse. In our system, the solar wind will inevitably erode Earth's magnetosphere—even if the planet avoids being swallowed.
This would strip away much of our atmosphere, rapidly eradicating any surviving life.
"We know past solar winds eroded Mars' atmosphere, which lacks a global magnetosphere like Earth's," says lead author Aline Vidotto of Trinity College Dublin. "What surprised us is how future solar winds could devastate even magnetically shielded planets."
Planets would need a magnetic field 1,000 times stronger than Earth's to endure.
This has profound implications for exoplanet habitability. White dwarfs, lacking stellar winds, are eyed for habitable worlds. Per this study, any life there must have evolved after the star's violent red giant phase ended.
