The Chemical Composition of Extrasolar Minor Planets

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

This project is an observational program to determine the abundances of select white dwarfs as a method of measuring the bulk compositions of extrasolar minor planets. It is motivated by a recent analysis of Keck I spectra of the white dwarf GD 362 whose photospheric abundances are naturally understood as resulting from the destruction of a minor planet similar in composition to the Earth/Moon system which is depleted in volatiles like carbon and sodium by more than a factor of 10. This suggests that white dwarfs with an infrared excess, such as GD 362, have accreted debris from asteroids that strayed within the star's tidal radius and that the atmospheres of these white dwarfs thus provide a powerful and currently unique opportunity to measure the bulk compositions of extrasolar minor planets. Here, Professor Jura will use the Keck I telescope and HIRES spectrograph to obtain spectra of additional white dwarfs with an infrared excess (presumably the result of a dust disk inside the tidal radius) and determine the abundances of externally contaminated elements (including volatile versus refractory elements). White dwarfs without infrared excesses will also be observed to evaluate the role/possibility of interstellar accretion. The resulting data may well enable a more comprehensive understanding of the existence and frequency of extrasolar Earth-like planets. This project will directly support science education at UCLA and the education/training of a graduate student whose thesis will be based on these data.