Two hundred and eighty-nine days: that's how long one rotation of the white dwarf white dwarf WD 1532+129 takes. This is not just a record: on its surface, near the magnetic poles, scars of iron and other metals appear — silent testimony to planets it has devoured.
From 2019 to 2026, the FORS2 spectropolarimeter on the Very Large Telescope monitored the star using spectroscopy and polarimetry. It measured the magnetic field via the Zeeman effect — the splitting of spectral lines predicted by Maxwell's equations. Simultaneously, photometric surveys ZTF, ATLAS, and GOTO recorded brightness variations. It turned out that the metal lines strengthen when a magnetic pole faces Earth. It's like scars on a face becoming more prominent under certain lighting.
Each such scar tells a story. When the white dwarf pulls in debris from exoplanets, the magnetic field funnels material to the poles like an invisible sculptor, leaving chemical reliefs on the surface. Unlike most stars, where convection quickly erases such traces, here the scars persist for billions of years. Modeling showed that the enhancement of heavy elements in the polar regions reaches 0.2 dex — a real concentration of metals, not just a magnetic boosting of lines. The light curves are synchronous across different filters and show that the polar regions are slightly dimmer: perhaps convection is suppressed.
The slow rotation of WD 1532+129 invites speculation about its past. Perhaps its progenitor was a magnetic Ap star — then scars appeared early in its youth. Now, cooling for 4 billion years, this white dwarf continues to preserve the memory of lost worlds. Magnetically guided accretion of material turns out to be the rule rather than the exception for such objects, and this changes our understanding of stellar evolution. It rotates, showing us first one magnetically marked pole, then the other, like a last witness to an ancient planetary catastrophe.
This white dwarf's spin period is a near match for that of Venus — a planet that itself turns at an almost unimaginably sluggish pace. The old record of 17,86 days, held by WD 2316+123, had stood unbroken since 1991.