This artist’s impression shows the magnetic white dwarf WD 0816-310, where astronomers have found a scar imprinted on its surface as a result of having ingested planetary debris. Credit: ESO/L. Calçada
Key points:
- Researchers recently observed a “scar” on the the white dwarf WD 0816-310—an Earth-sized remnant of a star similar to our Sun.
- The scar formed by a concentration of metals imprinted on the white dwarf’s surface.
- Astronomers hope to harness the power of this new observation to uncover the bulk composition of exoplanets and understand how planetary systems remain dynamically active, even after “death.”
Scientists know that when a star like our Sun reaches the end of its life, it can ingest surrounding planets and asteroids. Now, a new study in The Astrophysical Journal Letters, adds a new layer of understanding by identifying a unique signature for the process.
Researchers used the European Southern Observatory’s Very Large Telescope (ESO’s VLT) to observe the surface of the white dwarf WD 0816-310—an Earth-sized remnant of a star similar to our Sun. They employed a specific instrument on the VLT called FOR2 that allowed them to detect the metal scar and connect it to the star’s magnetic field. They also relied on archival data from the VLT’s X-shooter instrument to confirm their results.
The team found that the star’s magnetic field played a role in cannibalizing pieces of the surrounding planetary system. This process resulted in a scar formed by a concentration of metals imprinted on the white dwarf’s surface.
The team determined that strength of the metal detection changed as the star rotated, meaning that the metals were concentrated on a specific area of the white dwarf surface rather than spread across it. They found that these changes were aligned with changes in the magnetic field—indicating that the magnetic field funneled metals on to the star to create the scar.
“Surprisingly, the material was not evenly mixed over the surface of the star, as predicted by theory,” explained study co-author John Landstreet, professor at Western University. “Instead, this scar is a concentrated patch of planetary material, held in place by the same magnetic field that has guided the infalling fragment. Nothing like this has been seen before.”
Looking ahead, the team hopes to harness the power of the new observation to uncover the bulk composition of exoplanets. Their techniques may also be used to further understand how planetary systems remain dynamically active, even after “death.”