Peering inside extrasolar rocky bodies

Abstract

Exoplanets\nThe oxygen fugacity of a rock, fO2, is a measure of how oxidizing or reducing its surroundings were when the rock formed. Different minerals form at different fO2 and have different physical properties, so the internal structure of an exoplanet depends on this value. Doyle et al. exploited the signature left behind when rocky bodies impact a white dwarf—the remnant of a dead star. By examining the rock-forming elements left on the surface of each white dwarf, they determine fO2 in the impacting body. Six systems all had similar fO2 to bodies in the Solar System, consistent with the idea that rocky exoplanets often have internal properties similar to those of Earth and Mars.\n\nScience , this issue p. [356][1]\n\n [1]: /lookup/doi/10.1126/science.aax3901