Like using a time machine to peer into the distant future
Five billion years hence, our sun will exhaust its fuel, swell into a red giant consuming Mercury, Venus, and Earth, then collapse into a white dwarf — a fate now illuminated not by prophecy, but by science. Astronomers at the University of St Andrews, wielding the James Webb Space Telescope, have studied a Jupiter-sized planet orbiting a stellar corpse 80 light-years away, finding in its survival and warmth a mirror of our solar system's distant end. The planet WD 1856 b should not exist so close to its dead star, yet it does — a cosmic anomaly that reveals how worlds can outlast the deaths of their suns, even as others, like our own Earth, will not.
- Earth faces guaranteed destruction in roughly 5 billion years when the sun expands into a red giant and incinerates the inner planets — this is no longer conjecture but scientific conclusion.
- The puzzle at the heart of the research is a planet that defies its own destruction: WD 1856 b orbits closer to its dead star than it should have been able to survive, demanding an explanation.
- Using Webb's ability to analyze a grazing transit, scientists detected the planet running 240 degrees hotter than expected — that excess heat became the critical clue to reconstructing its entire history.
- Working backward from the temperature, researchers determined the planet migrated inward billions of years after stellar death, dragged by the gravity of companion stars in a triple-star system.
- The study lands as both a warning and a wonder — Earth will be ash, but some worlds can survive stellar death and find new orbits, new dynamics, even new futures around a white dwarf's dim glow.
Five billion years from now, the sun will exhaust its hydrogen, balloon into a red giant more than a hundred times its current size, and incinerate Mercury, Venus, and Earth. It will then shed its outer layers and collapse into a white dwarf — a stellar corpse no larger than our planet. This is the conclusion of a new study by astronomers at the University of St Andrews, who used the James Webb Space Telescope to study a world that has already lived through exactly this catastrophe.
The planet, WD 1856 b, is Jupiter-sized and orbits a white dwarf 80 light-years away. Discovered in 2020, its mere existence is the mystery: it circles its dead star so closely that it should have been destroyed during the star's dying phase. Lead author Ryan MacDonald called it "quite the oddball." The central question was straightforward but profound — how did it survive?
The team observed the planet in a grazing transit, its edge barely overlapping the star's disk, allowing them to estimate its mass and probe its atmosphere. The decisive clue was temperature: the planet measured roughly 126 degrees Celsius, about 240 degrees warmer than the white dwarf's radiation alone could explain. Co-author Christopher O'Connor used planetary cooling models to trace that heat backward in time, concluding the planet was dramatically warmed somewhere between three and five and a half billion years after its star's death.
The explanation: the planet originally orbited at a safe distance, surviving the red giant phase, then migrated inward over billions of years under the gravitational pull of companion stars in a triple-star system. That ancient heating still radiates today — and Webb was sensitive enough to detect it.
For Earth, the lesson is sobering. Our planet will not survive our sun's death. But WD 1856 b shows that stellar death is not the end for every world. MacDonald described the study as "like using a time machine" — a glimpse not of our fate, but of what might stir in the long aftermath, around the white dwarf our sun will one day become.
Five billion years from now, the sun will exhaust the hydrogen that has fueled it since the solar system's birth. It will swell into a red giant, ballooning to more than a hundred times its current size, and in doing so, it will incinerate Mercury, Venus, and likely Earth as well. Then it will shed its outer layers and collapse into a white dwarf—a stellar corpse the size of our planet, still radiating heat but no longer capable of sustaining life. This is not speculation. It is the conclusion of a new study by astronomers at the University of St Andrews in Scotland, who have used the James Webb Space Telescope to peer into our solar system's distant future by studying a world that has already lived through this cosmic catastrophe.
The planet they examined is called WD 1856 b, a Jupiter-sized world orbiting a white dwarf star some 80 light-years away. It was discovered in 2020, but what makes it remarkable is not just its existence—it is the fact that it exists at all. The planet orbits so close to its dead star, just 50 times the distance between Earth and the sun, that it should have been obliterated when the star was dying. Yet here it is, intact, circling a stellar remnant that is only the size of Earth while the planet itself is seven times larger. Ryan MacDonald, the study's lead author, described it as "quite the oddball." The question that drove the research was simple but profound: how did this world survive?
To answer it, the team used Webb to observe the planet passing in front of its star in what astronomers call a grazing transit—the planet's edge just barely overlapping the star's disk. This technique allowed them to measure the planet's mass, somewhere between four and eleven times that of Jupiter, and to analyze its atmosphere by watching how starlight filtered through it. But the most revealing measurement came from the planet's temperature. The researchers found it was roughly 126 degrees Celsius, about 240 degrees hotter than it should be if the white dwarf's radiation were its only heat source. That excess warmth was the key to unlocking the planet's history.
Christopher O'Connor, a co-author from Northwestern University, used models of how planets cool over time to work backward from the current temperature. The team concluded that the planet must have been heated sometime between three and five and a half billion years after its star became a white dwarf. This timing pointed to a specific scenario: the planet had originally orbited at a safe distance, far enough away to survive the red giant phase. Only later did it migrate inward, drawn by the gravitational influence of other stars in what turned out to be a triple star system. As it spiraled closer to the white dwarf, the intense gravity heated it dramatically. That residual warmth, still radiating into space after billions of years, is what Webb detected.
The implications for Earth are sobering but distant. Our sun will follow the same path, and our planet will not survive it. But the research also suggests that stellar death is not necessarily the end for all worlds. Some planets, like WD 1856 b, can endure the destruction of their parent star and go on to experience new orbits, new dynamics, new futures in the aftermath. MacDonald called the study "like using a time machine to peer into the distant future of our solar system." It is a glimpse of what lies ahead—not for us, but for whatever worlds might circle the white dwarf our sun will become, long after Earth has been reduced to ash.
Notable Quotes
The planet is quite the oddball. 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.— Ryan MacDonald, University of St Andrews
Stellar death is not the end—some planets experience a vibrant and lively future after the death of their star.— Ryan MacDonald
The Hearth Conversation Another angle on the story
When you say Earth will be destroyed, do you mean vaporized entirely, or just rendered uninhabitable?
The sun will expand so far that Earth's orbit will be inside the star itself. There won't be much left to recognize. Mercury and Venus go first, but Earth follows.
So this study is really about understanding what happens to planets after their star dies. Why does that matter to us now?
Because we can't watch our own solar system's future directly. By studying WD 1856 b—a planet that has already lived through this—we're seeing a kind of preview. It's the closest thing we have to a time machine.
The planet is seven times larger than the star it orbits. How is that even physically possible?
It's unusual, yes. The white dwarf is incredibly dense—all the mass of the sun compressed into something Earth-sized. So even though the planet is huge, the star's gravity still dominates.
And the fact that it's so hot—that was the breakthrough?
Exactly. They measured a temperature that couldn't be explained by the star's current radiation. That excess heat was a fossil, essentially. It told them when and how the planet must have moved into its current orbit.
Does this mean other planets in our solar system might survive when the sun dies?
The gas giants—Jupiter, Saturn, Uranus, Neptune—might have a chance. They're far enough away that they could escape the red giant phase. But Earth, Venus, Mercury? No. They're too close.