When the Sun exhausts its hydrogen fuel in roughly 5 billion years, it will swell into a red giant, violently shedding layers of plasma and incinerating the inner planets. The remaining core will collapse into a white dwarf—a dense, Earth‑sized remnant that shines like a stellar diamond while its outer layers form a luminous planetary nebula.
What will become of Earth and any other surviving worlds? A team of astronomers from the University of Warwick has developed a preliminary “survival guide” based on dynamical simulations, revealing that the smallest, most compact planets have the best chance of withstanding the harsh tidal forces of a white dwarf.
White dwarfs pack almost the entire mass of their progenitor star into a volume only slightly larger than Earth. This extreme density generates a gravitational field so strong that a planet straying too close experiences differential forces—tides—that can rip it apart. The critical distance at which a planet’s self‑gravity can no longer hold it together is known as the destruction radius. Beyond this radius, the planet survives; inside it, the planet is shredded into dust that often forms a circumstellar disk.
The study found that a planet’s internal viscosity—its resistance to deformation—plays a decisive role. Low‑viscosity worlds, comparable in consistency to Saturn’s moon Enceladus, are vulnerable even beyond five times the destruction radius. In contrast, high‑viscosity, metal‑rich bodies can endure orbits as close as twice the destruction radius. Recent observations of a dense “heavy‑metal” object orbiting a white dwarf inside a dusty disk support this, suggesting it is the metallic core of a former planet that survived tidal disruption.
While the simulations treat homogeneous planets, Earth’s layered structure—core, mantle, crust—introduces additional complexities. Lead author Dimitri Veras notes, “A multi‑layer planet would be significantly more complicated to calculate, but we are exploring that possibility.” Until such models are available, the fate of Earth remains uncertain, though it is unlikely to survive the Sun’s red‑giant phase.
These insights will aid the growing catalog of exoplanets found around white dwarfs, helping astronomers infer planetary composition from orbital behavior.
For a broader look at our stellar neighbors, consider Sara Gillingham’s illustrated guide Seeing Stars: A Complete Guide to the 88 Constellations. Purchasing through HowStuffWorks supports the site.
According to EarthSky, a white dwarf is the remnant core of a dead star.
According to Space.com, a white dwarf cools over time and eventually becomes a black dwarf.
The American Museum of Natural History states that a white dwarf can explode as a supernova if it accretes enough mass to reignite nuclear fusion.
If a low‑viscosity planet ventures too close, the white dwarf’s intense gravitational tides can tear it apart.
According to National Geographic, a white dwarf’s surface temperature can exceed 180,000 °F.
