2024-02-28 12:00:16
At the end of their life, when stars like the Sun bow out, they do not disappear without a trace. They can engulf the planets and asteroids that have accompanied them throughout their existence. This artist’s impression shows the magnetic white dwarf WD 0816-310, where astronomers discovered a scar imprinted on its surface resulting from the ingestion of planetary debris.
Credit: ESO/L. Calçada
An international team of astronomers, using the Very Large Telescope (VLT) of the European Southern Observatory (ESO) located in Chile, has just revealed for the first time a unique scar on the surface of a white dwarf, testimony to this cosmic process.
The white dwarf WD 0816-310, an Earth-sized remnant of a star similar to our Sun, although slightly more massive, sports a concentration of metals on its surface. This “scar” is the direct result of the ingestion of planetary debris, potentially including a fragment the size of Vesta, the second largest asteroid in our solar system. This discovery, published in The Astrophysical Journal Letters, sheds new light on the crucial role of the star’s magnetic field in this process.
The researchers observed that the detection of metals on WD 0816-310 varied with the star’s rotation, indicating that these metals were concentrated in a specific area rather than evenly distributed across its surface. This concentration of metals is synchronized with variations in the white dwarf’s magnetic field, suggesting that the metal scar lies on one of its magnetic poles. This process, by which the magnetic field channels metals toward the star, creates a distinct scar. This phenomenon is reminiscent of the mechanisms at work in the formation of auroras on Earth and Jupiter, where the magnetic field guides the ionized material towards the poles.
This study also illustrates how planetary systems can remain dynamically active, even following the “death” phase of their central star. Observations made with the VLT and the FORS2 instrument, along with archived data from the X-shooter instrument, were crucial in linking the metallic scar to the white dwarf’s magnetic field.
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