A Jupiter-Like ‘Oddball’ Planet Survived Its Star’s Death. It May Show What Happens After Our Sun Dies

A dead-star planet may preview our solar system’s fate.

03 Jul 2026, 14:14 by Jordan Strickler · ZME Science

Artists impression of exoplanet WD 1856 b transiting its ‘dead’ host star. Credit: ESA

Researchers have discovered a planet which, by all intents and purposes, should not be there.

The world, coined WD 1856 b, is slightly larger than Jupiter and circles a dead star only about the size of Earth. Every 1.4 days, it whips around the white dwarf WD 1856+534, a stellar corpse approximately 80 light-years from Earth. The planet is so large compared with its host that the system looks almost inverted: a giant world eclipsing a tiny stellar remnant.

“The planet is quite the oddball,” said Ryan MacDonald, an astronomer at the University of St Andrews and lead author of the new study. “It’s about the size of Jupiter, but the white dwarf it orbits is the size of Earth, so the planet is seven times larger than its star.”

But the strangest part is not that WD 1856 b exists. It is where it exists.

The planet orbits about 50 times closer to its star than Earth orbits the sun. Had it always been there, it almost certainly would have been destroyed when its star swelled into a red giant. Instead, new observations from the James Webb Space Telescope suggest WD 1856 b survived at a safer distance, then moved inward billions of years after its star had already died.

The findings, published in Nature, offer one of the clearest glimpses yet of what may happen to giant planets after sun-like stars reach the end of their lives. That makes WD 1856 b more than a cosmic curiosity. It is a possible preview of our own solar system’s distant future.

A Preview for the Great End

In approximately five billion years, the sun will exhaust the hydrogen fuel in its core. It will swell into a red giant, expanding more than 100 times its current size. Mercury and Venus are doomed. Earth may be swallowed too, or at least scorched beyond recognition. After that violent phase, the sun will shed its outer layers and leave behind a white dwarf — a dense, fading ember of a star.

What happens to Jupiter, Saturn, Uranus and Neptune after that is much less certain.

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“Our findings have bearing on the long-term fate of our solar system,” said Christopher O’Connor, an astrophysicist at Northwestern University and co-author of the study. “In roughly five billion years, our sun will die, and we don’t know precisely what will happen to the planets at that time.”

WD 1856 b gives astronomers a way to study that question without waiting billions of years. It is a gas giant orbiting the remnant of a sun-like star, a system where the disaster has already happened and the aftermath is still unfolding.

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“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,” MacDonald said. “It’s like using a time machine to peer into the distant future of our Solar System.”

The planet was first discovered in 2020 using NASA’s Transiting Exoplanet Survey Satellite (TESS) and the Spitzer Space Telescope. Since then, scientists have puzzled over how such a large planet could end up so close to a white dwarf and remain intact.

Find It While It’s Hot

The new study used Webb to watch WD 1856 b pass in front of its star. The transit lasted only eight minutes since white dwarfs are faint compared with the kinds of stars Webb usually studies. Despite this though, Webb gathered enough light to measure the planet’s atmosphere, temperature and mass.

The team found WD 1856 b is between about four and 11 times the mass of Jupiter. They also detected signs of methane, clouds or hazes, and other hydrocarbons in its atmosphere — the first time astronomers have characterized the atmosphere of a planet transiting a dead star.

Then came the real clue: the planet is too warm.

WD 1856 b has a temperature of roughly 400 Kelvin, or about 260 degrees Fahrenheit. That is far hotter than expected if the planet were only being warmed by the faint light of its white dwarf. The dead star can account for only a much colder world.

Something else must have heated the planet. But whatever that something was, it is not happening now. The planet appears to be cooling from a past event.

That lingering heat helped the researchers reconstruct WD 1856 b’s history. By combining Webb’s measurements with models of how giant planets cool over time, they found the planet was likely reheated between 3 and 5.5 billion years after its host became a white dwarf.

That timing is key. If WD 1856 b had been swallowed by the star during the red giant phase and somehow survived inside the stellar envelope, the heating would have happened much earlier. Instead, the evidence points to a later migration.

The likely story is that WD 1856 b once orbited much farther out, beyond the reach of the red giant’s destruction. Later, gravitational nudges from other objects in the system — possibly companion stars, since WD 1856+534 is part of a triple-star system — stretched and tilted the planet’s orbit. Over time, close passes near the white dwarf raised tides inside the planet, heating it and pulling it into the tight orbit astronomers see today.

“As the planet moved inwards, its interactions with the strong gravity of the white dwarf will have caused it to warm up considerably, and it has been cooling ever since,” O’Connor said.

That does not mean Jupiter will follow the same path after the sun dies. Our solar system is not arranged like WD 1856+534. But the discovery shows that planetary systems do not simply freeze in place after stellar death. They can keep rearranging themselves for billions of years.

The study also opens a new door for the mighty Webb telescope. If astronomers can measure methane, haze and heat from a planet crossing a dead star in an eight-minute transit, they may be able to study more worlds around white dwarfs in the years ahead.