Christopher J. Manser, Boris T. Gänsicke, Siegfried Eggl, Mark Hollands, Paula Izquierdo, Detlev Koester, John D. Landstreet, Wladimir Lyra, Thomas R. Marsh, Farzana Meru, Alexander J. Mustill, Pablo Rodríguez-Gil, Odette Toloza, Dimitri Veras, David J. Wilson, Matthew R. Burleigh, Melvyn B. Davies, Jay Farihi, Nicola Gentile Fusillo, Domitilla de Martino, Steven G. Parsons, Andreas Quirrenbach, Roberto Raddi, Sabine Reffert, Melania Del Santo, Matthias R. Schreiber, Roberto Silvotti, Silvia Toonen, Eva Villaver, Mark Wyatt, Siyi Xu, Simon Portegies Zwart. 2019. A planetesimal orbiting within the debris disc around a white dwarf star. Science 364, 6435, 66-69 DOI: 10.1126/science.aat5330
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.