UCLA

Evidence is convincing that a big fraction of extrasolar planetesimals can survive the red giant stage of a star and persist into the white dwarf phase. We argue that eventually, some of them do get perturbed into the tidal radius of the white dwarf and disrupted, creating a dusk disk and polluting the star's pure hydrogen or helium atmosphere at the same time. I have been performing multi-wavelength observations to study these intriguing systems. With Spitzer/IRAC, I find a depletion of dust disk around cool white dwarfs relative to the warmer sample, possibly due to accretion from cometary objects. With the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope and the High- Resolution Echelle Spectrometer (HIRES) on Keck, I find that to zeroth order, the elemental compositions of extrasolar planetesimals very much resemble that of bulk Earth. A more detailed comparison with the solar system meteorites shows that post-nebular processing is common among extrasolar planetesimals. Overall, the bulk composition of Earth is normal compared to the current sample of extrasolar planetesimals.