A nuller is an optical instrument, e.g., a beam combiner for nulling interferometry[1], used to block or cancel out a strong source so that fainter signals near that source can be observed. This is typically useful to detect off-axis exoplanet or exozodiacal dust by interferometrically nulling out the on-axis parent star.
The VLT interferometer’s visiting instrument Asgard’s[2] submodule NOTT (Nulling Observations of exoplaneTs and dusT) contains such a nuller to combine four telescope signals to perform nulling interferometry[3].
Nulling interferometry
Nulling interferometry evolved from traditional stellar interferometry. The key difference is that it induces a 180-degree phase shift, for example, in one beam of a two-telescope interferometer. This creates destructive interference on the optical axis (where the star is) and constructive interference for off-axis objects (like planets). A technique initially proposed by Australian-American astronomer Ronald N. Bracewell in 1978 [4].
A different technique is called a coronagraph, using a physical obstacle to block the unwanted signals.
See also
References
- ^ Bracewell, R. N. (1978). “Detecting nonsolar planets by spinning infrared interferometer”. Nature. 274 (5673): 780–781. doi:10.1038/274780a0. ISSN 1476-4687.
- ^ Martinod, Marc-Antoine; Defrère, Denis; Ireland, Michael; Kraus, Stefan; Martinache, Frantz; Tuthill, Peter; Bigioli, Azzurra; Bouzerand, Emilie; Bryant, Julia; Chhabra, Sorabh; Courtney-Barrer, Benjamin; Crous, Fred; Cvetojevic, Nick; Dandumont, Colin; Ertel, Steve (2023-06-27). “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. 9 (02). doi:10.1117/1.JATIS.9.2.025007. hdl:10150/673745. ISSN 2329-4124.
- ^ Sanny, Ahmed; Labadie, Lucas; Gross, Simon; Barjot, Kévin; Laugier, Romain; Garreau, Germain; Martinod, Marc-Antoine; Defrère, Denis; Withford, Michael J. (2026-01-01). “Asgard/NOTT: L-band nulling interferometry at the VLTI – III. The mid-infrared integrated optics beam combiner for NOTT”. Astronomy & Astrophysics. 705: A37. doi:10.1051/0004-6361/202555865. ISSN 0004-6361.
- ^ Bracewell, R. N. (1978). “Detecting nonsolar planets by spinning infrared interferometer”. Nature. 274 (5673): 780–781. doi:10.1038/274780a0. ISSN 1476-4687.
External links
- Interferometric Nulling at TNO
- Nulling interferometer basics
- Tutorial on nulling interferometry
- Progress Toward Astronomical Nulling (Criteria governing efficacy of nulling interferometry), Chapter 10 of the Terrestrial Planet Finder (TPF): A NASA Origins Program to Search for Habitable Planets – JPL Publication 99-003, May 1999
- Interactive “virtual” interferometer