Potential refuge in the cosmos
Astronomers have discovered an Earth-like planet orbiting a star 4,000 light-years away, offering potential clues about Earth’s distant future. This rocky planet, with a mass similar to Earth’s, orbits a white dwarf in the constellation Sagittarius.
This finding hints at hope for Earth’s survival when our sun reaches its final stages, suggesting it may avoid being engulfed by the sun’s expansion. This opens up possibilities for human migration within the outer solar system, with moons like Europa, Callisto, and Ganymede near Jupiter, or Enceladus near Saturn, as potential future havens for humanity.
What is a white dwarf?
A white dwarf is the remnant of a star that has exhausted its nuclear fuel and shed its outer layers. It represents the ultimate fate of stars like our sun. As the sun depletes its fuel, it will expand into a red giant before shrinking into a white dwarf. How far it expands will determine which planets are engulfed—Mercury and Venus are expected to be consumed, but Earth’s fate remains uncertain.
In a study published in Nature Astronomy, researchers from the University of California, Berkeley, observed the system KMT-2020-BLG-0414 using the Keck Telescope in Hawaii. This system contains a white dwarf star with an Earth-sized planet orbiting at twice the Earth-sun distance. Accompanying the planet is a brown dwarf, a celestial body approximately 17 times the mass of Jupiter.
“This supports the idea that, as the sun becomes a red giant, its mass loss could drive the planets into more distant orbits, potentially sparing Earth,” said Jessica Lu, an associate professor of astronomy at UC Berkeley. “Whether life could endure through that red giant phase is unknown, but the important part is that Earth might not be swallowed.”
Earth’s billion-year timeline
Despite this optimistic scenario, scientists emphasize that Earth has only about a billion years left before it becomes uninhabitable. “Long before the sun’s red giant phase, Earth’s oceans will likely be vaporized by a runaway greenhouse effect,” explained Keming Zhang, lead author of the study and now an Eric and Wendy Schmidt AI in Science postdoctoral fellow at UC San Diego.
Migration to the outer solar system?
As Earth’s climate becomes increasingly inhospitable, the solar system’s habitable zone may shift outward to the orbits of Jupiter and Saturn, potentially turning their icy moons into ocean worlds capable of supporting life. “Humanity might one day migrate to those outer moons,” suggested Zhang, envisioning future generations thriving on distant moons as Earth’s resources dwindle.
This discovery not only underscores the resilience of planetary systems orbiting white dwarfs but also illuminates potential paths for humanity’s survival, far beyond the confines of Earth.
