Planets are supposed to form alongside their stars, but new research suggests that planets may also be born later, from the debris of a dying star, and one such unique alien world may be sitting very close to HS 0209+0832, a hot, young white dwarf located 270 light-years away in the constellation of Cetus.
An artist’s impression of the planet HS 0209+0832b. Image credit: NASA / ESA / Leah Hustak, STScI.
White dwarfs, the dense remnants of Sun-like stars, often show metals in their atmospheres.
These metals normally come from shattered asteroids and other rocky bodies, and their makeup tends to resemble solar system material.
HS 0209+0832, a hot, young white dwarf about 5 million years old, is a strange exception.
“HS 0209+0832’s far-ultraviolet spectrum obtained in 1999 with the Space Telescope Imaging Spectrograph (STIS) onboard the NASA/ESA Hubble Space Telescope revealed the presence of carbon, aluminum, silicon, calcium, titanium, nickel and zinc in the atmosphere, as well as 100 lines that could not be identified,” said University of Warwick astronomer Jamie Williams and colleagues.
“Whereas the presence of helium and metals indicates ongoing accretion, the nature of that external source remained unexplained.”
In the study, the astronomers reanalyzed archival data from the STIS instrument aboard Hubble, the FUSE and UVES instruments mounted on ESO’s Very Large Telescope, along with the broad-band photometric data from Pan-STARRS and ESA’s Gaia satellite.
Niobium was more than three orders of magnitude more abundant than in the Sun, and they found no niobium in 33 other metal-polluted white dwarfs they checked.
Nickel appears to outweigh iron by at least a factor of two, whereas in the Sun, Earth and primitive meteorites iron dominates by a wide margin.
These abundances don’t match any known meteorite or any other white dwarf’s accreted material, and the star isn’t swallowing a volatile-rich icy body either.
“Niobium and other elements heavier than iron are astronomically special because, unlike many common elements, they are not formed in the cores of stars by thermonuclear fusion,” said Dr. Nicholas Stone, a theoretical astrophysicist at the University of Wisconsin – Madison.
“Instead, these heavy elements can only be synthesized in the exotic conditions that briefly emerge inside dying stars.”
“The presence of niobium is a signpost of these ‘death’ throes, and the expulsion of the dying star’s innards into space.”
According to the researchers, as a star swells into an asymptotic giant branch (AGB) giant, it forges many heavy elements through the slow neutron-capture s-process and sheds them in winds.
They argue that material from those winds, rich in carbon and s-process elements, could have formed a disk around the star in its late life, and that a giant planet could have grown within it.
Models of AGB nucleosynthesis predict exactly this kind of enhancement in niobium, nickel, copper and zinc, with little change to oxygen, silicon, calcium or iron.
The white dwarf’s composition demonstrates that it is accreting from a second-generation planet candidate.
“If the second-generation planet is there, I think it is likely to survive,” Williams said.
“Eventually the white dwarf will cool and then maintain a consistent temperature, with the planet in its stable habitable zone for millions of years.”
Using data from NASA’s Transiting Exoplanet Survey Satellite (TESS), the scientists found a repeating brightness variation with a period of about 4.4 days. This period is far longer than the typical white dwarf spin period of around 1.25 days.
The signal could come from the day-night temperature contrast of a giant planet orbiting at roughly 0.04 AU (astronomical units).
“Rather than the white dwarf stage being a kind of epilogue to the story of a star and its planets, this research points to the systems we are familiar with only being the first chapter of a potentially much longer tale, with some new characters showing up. That’s a really exciting prospect to pursue,” Williams said.
The team’s results were published this week in the journal Nature Astronomy.
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J.T. Williams et al. Discovery of a second-generation planet candidate accreting onto a white dwarf. Nat Astron, published online October 5, 2026; doi: 10.1038/s41550-026-02983-7
