Astronomers have determined that Earth will be destroyed when the sun dies in approximately five billion years, according to a new study from the University of St Andrews. The research, published in the journal Nature, used the James Webb Space Telescope to observe a Jupiter-sized exoplanet called WD 1856 b orbiting a white dwarf—the remnant of a dead star—providing a glimpse into the solar system's distant future.
Sun's transformation into red giant will destroy inner planets
The study explains that in about five billion years, the sun will exhaust its hydrogen fuel and expand into a red giant star, swelling to more than 100 times its current size. This expansion will engulf and destroy Mercury, Venus, and likely Earth. After shedding its outer layers, the sun will end its life as a white dwarf.
Lead author Dr. Ryan MacDonald from the University of St Andrews described the exoplanet WD 1856 b as an 'oddball.' It is about the size of Jupiter but orbits a white dwarf the size of Earth, making the planet seven times larger than its star. The planet orbits at a distance 50 times closer than Earth's orbit around the sun, an 'extremely close' orbit that would have been impossible if the planet had always been there—it would have been obliterated during the red giant phase.
Using Webb telescope as a 'time machine'
The researchers used the James Webb Space Telescope to observe WD 1856 b during a 'grazing transit,' where only the top of the planet passed in front of the white dwarf. This allowed them to measure the planet's mass (between four and 11 times that of Jupiter) and temperature (around 400 Kelvin, or 126°C). The planet is significantly warmer than expected—about 240 degrees hotter than if it were only heated by the white dwarf's light.
Dr. MacDonald said: 'We're used to looking back in time when we use telescopes, but this is the first time we have been able to look forward to what might happen to the outer planets around the remnant of a Sun-like star. It's like using a time machine to peer into the distant future of our Solar System.'
Implications for outer planets like Jupiter and Saturn
The study also sheds light on the fate of gas giants like Jupiter and Saturn. Since WD 1856 b survived the death of its star, it suggests that similar planets in our solar system might also endure, though the inner planets will be destroyed. The residual heat observed in WD 1856 b is likely from being engulfed by the red giant or from inward migration.
The exoplanet WD 1856 b was first discovered in 2020 using NASA's Transiting Exoplanet Survey Satellite (TESS) and the Spitzer Space Telescope. It is located about 80 light-years from Earth, a distance that would take over one million years to travel with current rocket technology.
