Posted by A new study from NASA Goddard Space Flight Center warns that dust surrounding nearby stars could significantly distort future observations of Earth-like exoplanets. The research examines exozodiacal dust, or exozodi—micron-sized material produced by planetesimals and located within planetary systems’ habitable zones.
NASA’s proposed Habitable Worlds Observatory is designed to directly image and characterize approximately 25 potentially Earth-like planets around nearby Sun-like stars. However, light scattered by exozodi may blend with a planet’s faint reflected light and become one of the mission’s largest sources of astrophysical interference. Nearby Sun-like systems may contain a median of around three times more habitable-zone dust than the Solar System.
The researchers simulated modern and Archean Earth analogues observed by HWO, testing dust with gray, red, blue and Solar System-like optical properties. They then used an atmospheric retrieval model to examine how residual dust would affect measurements of oxygen, water and carbon dioxide. The simulations show that even one “zodi” of unremoved dust can reduce the apparent depth of visible molecular absorption features by as much as 50 percent. The effect generally becomes stronger at longer wavelengths. Residual exozodi may also flatten the Rayleigh-scattering slope and cause atmospheric models to miscalculate a planet’s molecular abundances, cloud cover, radius, temperature and surface pressure.
To preserve absorption-band depths, the remaining dust signal should be below one percent of the planet’s visible-light flux. Accurate molecular-abundance measurements may require contamination below 0.1 percent. For dusty systems, this could require post-processing that suppresses exozodi by factors of 100 to 1,000. Requirements may be less demanding when astronomers only need to confirm that a molecule is present. Higher spectral resolution could also increase tolerance to residual dust. The findings show that measuring and removing exozodi will be essential for HWO’s search for habitable and potentially inhabited planets.
