A planetesimal orbiting within the debris disc around a white dwarf star.

Manser, Christopher J; Gänsicke, Boris T; Eggl, Siegfried; Hollands, Mark; Izquierdo, Paula; Koester, Detlev; Landstreet, John D; Lyra, Wladimir et al. · Science · 2019

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Abstract

Many white dwarf stars show signs of having accreted smaller bodies, implying that they may host planetary systems. A small number of these systems contain gaseous debris discs, visible through emission lines. We report a stable 123.4-minute periodic variation in the strength and shape of the Ca ii emission line profiles originating from the debris disc around the white dwarf SDSS J122859.93+104032.9. We interpret this short-period signal as the signature of a solid-body planetesimal held together by its internal strength.