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We present evidence that excesses in Be in polluted white dwarfs (WDs) are the result of accretion of icy exomoons that formed in the radiation belts of giant exoplanets. Here we use excess Be in the white dwarf GALEX J2339-0424 as an example. We constrain the parent body abundances of rock-forming elements in GALEX J2339-0424 and show that the overabundance of beryllium in this WD cannot be accounted for by differences in diffusive fluxes through the WD outer envelope nor by chemical fractionations during typical rock-forming processes. We argue instead that the Be was produced by energetic proton irradiation of ice mixed with rock. We demonstrate that the MeV proton fluence required to form the high Be/O ratio in the accreted parent body is consistent with irradiation of ice in the rings of a giant planet within its radiation belt, followed by accretion of the ices to form a moon that is later accreted by the WD. The icy moons of Saturn serve as useful analogs. Our results provide an estimate of spallogenic nuclide excesses in icy moons formed by rings around giant planets in general, including those in the solar system. While excesses in Be have been detected in two polluted WDs to date, including the WD described here, we predict that excesses in the other spallogenic elements Li and B, although more difficult to detect, should also be observed, and that such detections would also indicate pollution by icy exomoons formed in the ring systems of giant planets.
It is difficult to study the interiors of terrestrial planets in the Solar System and the problem is magnified for distant exoplanets. However, sometimes nature is helpful. Some planetary bodies are torn to fragments and consumed by the strong gravit
The element beryllium is detected for the first time in white dwarf stars. This discovery in the spectra of two helium-atmosphere white dwarfs was made possible only because of the remarkable overabundance of Be relative to all other elements, heavie
Planetary systems can survive the stellar evolution, as evidenced by the atmospheric metal pollution and dusty disks of single white dwarfs. Recent observations show that 1 to 4 percent of single white dwarfs are accompanied by dusty disks, while the
Assuming our Solar System as typical, exomoons may outnumber exoplanets. If their habitability fraction is similar, they would thus constitute the largest portion of habitable real estate in the Universe. Icy moons in our Solar System, such as Europa
White dwarfs that have accreted planetary bodies are a powerful probe of the bulk composition of exoplanetary material. In this paper, we present a Bayesian model to explain the abundances observed in the atmospheres of 202 DZ white dwarfs by conside