Stellar Remnant HS 0209+0832 Consumes Its Own Second-Generation Offspring
Astronomers have identified the first strong hints of a newborn planet orbiting the white dwarf star HS 0209+0832, approximately half the mass of the Sun and heated to roughly 35,000 kelvin. In findings published in Nature Astronomy, researchers reported that the white dwarf is actively devouring the atmosphere of this second-generation planet, which formed from debris shed by the dying star rather than its initial birth clouds.
Chemical Anomalies Point to Stellar Cannibalism
When astronomers first observed HS 0209 using the Hubble Space Telescope in 1999, they detected an unexpected excess of helium in its atmosphere. Subsequent observations drawing on later Hubble data, the Far Ultraviolet Spectroscopic Explorer, and the Transiting Exoplanet Survey Satellite revealed a stark atmospheric pollution profile featuring three times the niobium abundance seen in the Sun’s spectrum, alongside heavy traces of copper and zinc.
Jamie Williams, an astronomer at the University of Warwick who led the study, noted the unique nature of the discovery. This white dwarf is unique because it has a lot of traces of copper, zinc, and niobium,
Williams said. Niobium is especially interesting because that’s the first time it’s ever been discovered in a white dwarf.
Additional perspective came from Juliette Becker, a planetary astronomer at the University of Wisconsin–Madison who was not involved with the research. I don’t know of any other source that comes close to being this strange,
Becker stated, adding that the profile differs sharply from existing stellar pollution patterns.
Mapping the Hot Jupiter
Data from the Transiting Exoplanet Survey Satellite tracked visible light fluctuations across a 4.4-day orbital period, capturing the day-night phase curve of what researchers categorize as a hot Jupiter. This planetary body coalesced from a disk of material cast off during the progenitor star’s final stages. Rather than surviving the host star’s death, this world emerged from the wreckage.
We have a white dwarf orbited by a disk of this kind of material,
Williams explained regarding the debris disk fragmentation that built the planet. This disk will fragment and then you’ll form a planet.
The stellar remnant subsequently began boiling off the newborn planet’s atmosphere, pulling a portion inward while expelling the rest into space. This dynamic accounts for the anomalous helium and heavy elements present in the white dwarf’s atmosphere.
James Webb Telescope May Detect More White Dwarf Planets
Researchers hope to use the James Webb Space Telescope to directly detect the exoplanet, which glows in infrared wavelengths due to intense stellar heating. Because similar second-generation planets orbit pulsars—the remnants of significantly more massive stars—astronomers consider it probable that white dwarfs frequently host comparable descendant worlds.
I also have a strong bias: Because there are pulsar second-generation planets, I think there must be also second-generation planets around white dwarfs,
Becker said. With HS 0209 presenting as a typical white dwarf despite its unusual chemistry, the system opens a new pathway for investigating planetary systems formed after stellar death.
