In roughly 5 billion years, our sun will begin dying — swelling to enormous size, swallowing the closest planets, then shedding its outer layers and collapsing into a dense stellar remnant known as a white dwarf. But new research suggests that some planets may endure long after that catastrophic transformation.
Scientists have now made detailed observations of a Jupiter-like planet beyond our solar system that has continued to exist for billions of years following its star’s death. The planet, known as WD 1856 b, sits 81 light-years from Earth in the constellation Draco. For reference, one light-year equals 5.9 trillion miles, or 9.5 trillion kilometers — the distance light covers in a single year.
Researchers determined that WD 1856 b has a mass roughly eight times that of Jupiter, the largest planet in our solar system. Its atmospheric temperature registers around 260 degrees Fahrenheit (127 degrees Celsius), which scientists say is surprisingly warm for a planet in its situation.
The planet now circles extremely close to the white dwarf — 50 times closer than Earth is to our sun — apparently having drifted inward over a long period of time. It completes a full orbit in just 1.4 days.
WD 1856 b serves as a real-world example of how planets can survive the death of their host star, which may mirror what happens to some planets in our own solar system when the sun eventually dies. However, scientists note that this planet’s situation involves some unusual circumstances. The white dwarf is actually part of a triple star system, alongside two smaller red dwarf stars, each about 30% of the sun’s mass — creating a complex gravitational environment.
Researchers are still working to understand exactly how WD 1856 b ended up in such a tight orbit around the white dwarf. “There are two main competing ideas for how WD 1856 b got into the tight orbit we observe today,” explained astrophysicist Christopher O’Connor of Northwestern University in Illinois, one of the study’s authors. The research was published in the journal Nature.
The first theory suggests the planet was actually swallowed during the star’s red giant expansion phase but managed to survive just outside the collapsing stellar core. The second theory holds that the planet was originally far enough away to avoid being consumed, but was later gravitationally nudged inward by the two nearby red dwarf stars.
WD 1856 b was first discovered in 2020, providing the earliest definitive proof that planets can outlive sun-like stars. This new study goes further, shedding light on the planet’s makeup and history. Scientists examined it using the James Webb Space Telescope and found it is composed primarily of hydrogen and helium — similar to Jupiter — but with an unusually high concentration of methane. Researchers believe its unexpected warmth comes from the gravitational forces exerted by the white dwarf as the planet’s orbit gradually tightened over time.
In a striking reversal of the usual size relationship between stars and planets, WD 1856 b is actually about 500 times larger in volume than the white dwarf it orbits. While stars are typically far bigger than their planets — the sun is roughly 1,000 times larger in volume than Jupiter — a white dwarf is extremely compact, only slightly bigger than Earth, though far more massive. The white dwarf in this system formed from a star up to twice the mass of our sun that died approximately 5 billion years ago.
As for what all this means for our own solar system, scientists say the picture is becoming clearer — at least for some planets. When the sun enters its red giant phase, it will balloon to about 200 times its current size, definitely engulfing Mercury and Venus in the process.
“The rest of the planets beyond Earth will be well beyond the sun’s maximum size, so they will most likely just continue to orbit the white dwarf left behind by the sun,” O’Connor said. “However, because the sun will lose about half of its mass as it becomes a white dwarf, we expect the survivors to gradually drift away until they reach about double their current orbital distances.”
Earth’s fate, however, remains an open question. “We cannot predict Earth’s future orbit well enough to know whether it will be inside or outside the ‘danger zone’ when the sun reaches the end of its life,” O’Connor said. “Fortunately, this is one problem we still have billions of years to figure out.”
