White dwarfs are the end state of most stars, including the Sun, after theyexhaust their nuclear fuel. Between 1/4 and 1/2 of white dwarfs have elementsheavier than helium in their atmospheres, even though these elements shouldrapidly settle into the stellar interiors unless they are occasionallyreplenished. The abundance ratios of heavy elements in white dwarf atmospheresare similar to rocky bodies in the Solar system. This and the existence of warmdusty debris disks around about 4% of white dwarfs suggest that rocky debrisfrom white dwarf progenitors' planetary systems occasionally pollute the stars'atmospheres. The total accreted mass can be comparable to that of largeasteroids in the solar system. However, the process of disrupting planetarymaterial has not yet been observed. Here, we report observations of a whitedwarf being transited by at least one and likely multiple disintegratingplanetesimals with periods ranging from 4.5 hours to 4.9 hours. The strongesttransit signals occur every 4.5 hours and exhibit varying depths up to 40% andasymmetric profiles, indicative of a small object with a cometary tail of dustyeffluent material. The star hosts a dusty debris disk and the star's spectrumshows prominent lines from heavy elements like magnesium, aluminium, silicon,calcium, iron, and nickel. This system provides evidence that heavy elementpollution of white dwarfs can originate from disrupted rocky bodies such asasteroids and minor planets.
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