Surviving planet offers clues to Solar System's future

Astronomers have discovered a planet that defied the odds by surviving the death of its star, providing a potential glimpse into the distant future of our own Solar System. The planet, known as WD1856b, is unusually large, about the size of Jupiter, and orbits a white dwarf star that is roughly the size of Earth.

This system is considered one of the strangest known because the planet orbits its star at an extremely close distance. Typically, stars are much larger than their planets. White dwarfs are the dense remnants of stars that have exhausted their fuel and died. When astronomers found this giant planet orbiting a dead star in 2020, they questioned how it survived the star's red giant phase, a period when stars swell to over a hundred times their original size and usually engulf nearby planets.

This survival is significant because when our Sun dies in about 5 billion years, it is expected to consume Mercury, Venus, and possibly Earth. The existence of WD1856b suggests that planets can migrate to safer orbits after a star's death, expanding the possibilities for where and when habitable planets might exist in the universe. Researchers used the James Webb Space Telescope to study the planet's atmosphere, mass, and temperature, which is warmer than anticipated.

They theorize that the planet originally orbited at a safe distance but migrated closer to the star billions of years after its death. Another possibility is that the gravitational pull of other stars in a triple-star system influenced WD1856b's orbit, allowing it to remain safe during the red giant phase and move closer much later. These observations offer crucial data on planetary migration and stellar evolution.