¹C.J.Manser et al. (>10)
Science 364, 66-69 Link to Article [DOI: 10.1126/science.aat5330]
¹Department of Physics, University of Warwick, Coventry CV4 7AL, UK. Reprinted with permission from AAAS

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.