Exozodiacal dust (exozodi) is the dust in the terrestrial (and habitable) zones around other stars. Exozodi is useful for studying rocky exoplanet formation, but it is also a source of noise for future missions to image Earth-like exoplanets. At a temperature of ~300 K, exozodi emits at ~10 microns. However, a detection of an infrared excess at this wavelength does not necessarily mean exozodi is present, because the location and temperature of dust are degenerate with the size of the grains. Warm, small, silicate grains exhibit distinctive solid state emission features in the mid-IR. I searched the Spitzer/IRS spectra of stars with debris disks and discovered previously unknown silicate features in 22 systems. With detailed fitting to the shapes of these features, I was able to break the degeneracy and accurately locate the dust. I found that the dust resided in the terrestrial zones of these systems, confirming the presence of exozodi. There may be undetected silicate features in the spectra of additional disks that could be observed with the improved sensitivity of JWST, providing a means to measure low-levels of exozodi in the near future.
See all the details of this project in our ApJ paper.