Astronomy: Red and white dwarfs caught consuming their orbiting objects (Nature Astronomy)
6 October 2026
Two dwarf stars may be gradually consuming their orbiting companions, according to two papers published in Nature Astronomy.
Planets and brown dwarfs can orbit red dwarfs, which are smaller than the sun, and are generally expected to remain separate until orbital changes or expansion of the evolving host star brings them into contact, potentially leading to their rapid destruction. White dwarfs are the small, dense remnants of these stars at end of their lives, typically only slightly larger than Earth. Some white dwarfs are surrounded by discs of debris produced by the destruction of these smaller companions, providing evidence that close-orbiting objects can be consumed as stars evolve.
Aaron Householder and colleagues analysed data from the Zwicky Transient Facility and identified a binary system (called ZTF J0440+2325) consisting of a brown dwarf and a red dwarf completing an orbit every 86.65 minutes. Using light measurements across five wavelength bands, the authors observed a bright, hot spot on the red dwarf. Their modelling suggests that material flows directly and steadily from the brown dwarf onto the red dwarf, creating the hot spot on the latter — a process that has not been directly observed before. The binary system could remain in this state for at least 10 million years and potentially for billions of years.
In a separate paper, Jamie Williams and colleagues reanalysed ultraviolet observations of a young white dwarf called HS 0209+0832 from several telescopes, including the Hubble Space Telescope and the Transiting Exoplanet Survey Satellite. They found an unusual chemical mix of high levels of heavy elements such as zinc, copper, and niobium around the white dwarf, but very little silicon and no iron. The star’s brightness also changed in a regular pattern every 4.39 days, which could be caused by an orbiting giant planet. The varying brightness may arise either from temperature differences between the planet’s day and night sides or from a tail of escaping gas crossing the line of sight. The chemical pattern suggests that the giant planet is likely to have formed from material expelled during the white dwarf ancestor’s final stages. The authors propose that the object is a candidate second-generation giant planet whose escaping atmosphere is feeding the white dwarf.
Together, the findings shed light on the evolution of low-mass binary systems and introduce a subcategory of second-generation planets around white dwarfs. Future work with more detailed modelling and larger surveys could help determine how these systems form and how common they are.
- Article
- Published: 05 October 2026
Householder, A., Shin, K., Burdge, K.B. et al. Stable mass transfer from a substellar object onto an M dwarf. Nat Astron (2026). https://doi.org/10.1038/s41550-026-02992-6
- Article
- Open access
- Published: 05 October 2026
Williams, J.T., Gänsicke, B.T., Stone, N.C. et al. Discovery of a second-generation planet candidate accreting onto a white dwarf. Nat Astron (2026). https://doi.org/10.1038/s41550-026-02983-7
News & Views: A white dwarf polluted by its own ashes
https://www.nature.com/articles/s41550-026-02982-8
© 2026 Springer Nature Limited. All Rights Reserved.
