The Large Binocular Telescope Interferometer, or LBTI, uses its nulling interferometric capabilities to study the brightness of warm dust floating in the orbital planes of other stars (called exozodiacal dust). In particular, the HOSTS survey (The Hunt for Observable Signatures of Terrestrial Planetary Systems) has studied dust in nearby stars’ habitable zones, where liquid water could exist on the surface of a planet. This project utilized LBTI’s nulling and the unique optical setup of LBTI to execute a large survey of the exozodiacal dust for a number of stars, including sun-like analogs which would be of particular interest for future space-based missions. The habitable zone dust is most emissive around 300K for which LBTI has the greatest sensitivity.
Interferometric Nulling paves the way, allowing us to separate the star’s overpowering light from the dim glow of circumstellar material. The LBTI Nulling Interferometer works such that the light is simultaneously be collected by two apertures at the end of the interferometer arms. One beam undergoes a half-wavelength phase shift, and combining the beams produces a destructive transmission fringe over the star. Any light fight from an exo-Earth or circumstellar material remains as it would be off-axis. SOUL LBTI AO plays a key role to stabilize the atmospheric perturbations that would otherwise prohibit the imaging of an otherwise “twinkling” star.
The ongoing studies of exo-zodiacal light are critical for finding planets and the studies of habitable zones, as well as for the preparation of space missions. Atmospheric induced noise remains prohibitive for observing rocky planets from the ground in the habitable zone, but pre observations with ground-based observatories using nulling can help guide observations with our space-based telescopes in the decades ahead.
The full Physics Today Paper can be found:
Eckhart Spalding, Denis Defrère, Steve Ertel (2022)