NOTT: the first nulling interferometer for the VLTI

ESO's Very Large Telescope Interferometer (VLTI) collects the light from several telescopes in order to synthetize a giant telescope whose angular resolution is equivalent to that a telescope with a diameter equal to the largest separation between the telescopes used. NOTT will leverage this sharp angular resolution of the VLTI with high-contrast capabilities in order to observe the inner region of planetary systems and discover new exo-planets. Image credit: ESO.

NOTT (formerly Hi-5) is the name of a project for a high-contrast instrument for the Very Large Telescope Interferometer (VLTI). Developing high-contrast capabilities has long been recognized as one of the top priorities for future interferometric instruments and the VLTI in particular (Mérand 2018). With baselines up to 200m, the VLTI can probe spatial scales well beyond what future 30m-class extremely large telescopes will be able to do and will remain a major facility over the next decades. Today, thanks to recent advances in integrated optics and new ideas in beam combination architecures (Martinache and Ireland 2018), it is possible to obtain observations at higher contrast with the VLTI and make progress in various scientific areas:
  • Planet formation and youg planets
  • Exozodiacal disks
  • Stellar physics: binarity accross the HR diagram
  • Extragalactic astrophysics
In addition, NOTT will serve as a key technology demonstrator for future major interferometric instruments with transformational goals such as PFI (planet formation) and LIFE (searching for biosignatures on remote planets, see also here). A kickoff meeting was held in Liège in October 2017 to discuss the science case and key technology requirements. The project status was presented at the VLT 2030 conference at ESO in June 2019 (see link to presentation below) and received full funding support in December 2019 with an ERC Consolidator grant (see SCIFY page).

More information can also be found in the references below:
  • Nulling interferometry overview link
  • Martinod et al., "High-angular resolution and high contrast observations from Y to L band at the Very Large Telescope Interferometer with the Asgard Instrumental suite", Journal of Astronomical Telescopes, Instruments, and Systems, Volume 9, id. 025007 (2023) link .
  • Laugier et al., "Asgard/NOTT: L-band nulling interferometry at the VLTI. I. Simulating the expected high-contrast performance", Astronomy \& Astrophysics, Volume 671, id.A110, 14 pp. link .
  • Defrère et al., "L-band nulling interferometry at the VLTI with Asgard/Hi-5: status and plans", SPIE proceedings, 2022 Arxiv SPIE .
  • Defrère D., "Exoplanet imaging by infrared interferometry: a new paradigm", ULiège colloquium, 2020 link.
  • Defrère et al., "Exoplanet charcterization with the VLTI", The Very Large Telescope in 2030 (June 2019), link.
  • Defrère et al., "Hi-5: a potential high-contrast thermal near-infrared imager for the VLTI", SPIE 10701, 2018 link.
  • Mérand, "The VLTI roadmap", ESO Messenger (March 2018), link.
  • Martinache and Ireland, "Kernel-nulling for a robust direct interferometric detection of extrasolar planets", A&A 619, 2018, link.
  • Defrère et al., "The path towards high-contrast imaging with the VLTI: the Hi-5 project", Experimental Astronomy 46, link.
  • Absil et al., "Performance study of ground-based infrared Bracewell interferometers. Application to the detection of exozodiacal dust disks with GENIE", A&A 448, 2006, link.