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1/23/20: SO/NSF's OIR Lab Joint Colloquium Series: Steve Ertel, LBTO


Title: Observing Habitable Zones with Precision Infrared Interferometry/The Context and Science Return from the LBTI/HOSTS Survey

Exozodiacal dust is warm and hot dust in the inner regions of planetary systems. In analogy to our Solar system’s zodiacal dust, it is located in and around a star’s habitable zone (HZ), and closer in. Studying the distribution, origin, and evolution of this dust provides us with crucial present-day insight into the architectures of planetary systems, in particular their inner regions. On the other hand, knowledge of the HZ dust levels around the target stars of future exo-Earth imaging missions is critical for the design and success of such missions as the presence of dust adds noise and confusion to these observations. Detecting the dust requires precision interferometry due to its proximity and high contrast to the host star.

Over the past years, our team has built the Large Binocular Telescope Interferometer (LBTI) and carried out the NASA funded HOSTS (Hunt for Observable Signatures of Terrestrial planetary Systems) survey with significant investment of time and resources from Steward Observatory. We used nulling interferometry on the Large Binocular Telescope Interferometer (LBTI) to suppress the bright star light and detected the thermal emission of the HZ dust in N band around a quarter of our target stars (10 of the 38 observed stars). We have reached typical sensitivities of a few ten times the Solar system dust level and have reached down to a few times the Solar system level for our most favorable stars. With a separate team, I have also used over the past decade optical long baseline interferometry to survey a large sample of stars for hotter dust even closer to the star, providing dozens of detections of hot dust (1000K to 2000K) at least a hundred times more abundant than in the Solar system.

I will review the results from these studies with particular focus on the recent HOSTS survey. I will also briefly discuss the LBTI as a high angular resolution, high contrast, low thermal background imager and interferometer for general astronomical observations at mid-infrared wavelengths.

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