Comptes Rendus
no. S2
Astrometry of directly imaged exoplanets with optical interferometry
[Astrométrie des exoplanètes par interférométrie optique astronomique]
Sylvestre Lacour1 
1 LESIA, Observatoire de Paris, Université PSL, CNRS, Université Paris Cité, Sorbonne Université, 5 place Jules Janssen, 92195 Meudon, France
Comptes Rendus. Physique, Online first (2023), pp. 1-14.

L’interférométrie aux longueurs d’ondes visibles a toujours été considérée comme une technique prometteuse mais difficile pour l’astronomie. Jusqu’à l’année 2018, sa sensibilité était limitée aux objets célestes les plus brillants, avec des magnitudes inférieures à 10. L’instrument GRAVITY, installé derrière le VLTI au Chili, a changé cela — grâce notamment à sa capacité de suivre et corriger le déplacement des franges et à son interféromètre double champ. Avec GRAVITY, l’on peut désormais observer des cibles très faibles. Cet article présente les différentes façons de faire de l’astrométrie avec un interféromètre optique. Il montre pourquoi l’interférométrie à double champ est devenue la technique clé pour les compagnons faibles. En prenant l’exemple de l’exoplanète HD 95086 b, nous montrons comment l’interférométrie à double champ peut détecter des exoplanètes aussi faibles que la magnitude 19,5. Nous expliquons également comment nous obtenons des précisions astrométriques de 10μas, et décrivons les biais restants qui peuvent entraver la mesure. Enfin, nous terminons en présentant les orbites de 10 exoplanètes dans 4 systèmes, et concluons sur les perspectives à plus long terme de cette technique.

Optical interferometry has always been seen as a promising but difficult technique for astronomy. Until the year 2018, it was excrucially limited in sensitivity to magnitudes below 10. However, thanks to the advent of the GRAVITY instrument, fringe tracking and dual field interferometry made it possible to observe very faint target. This paper presents the different techniques used by optical interferometry to perform astrometry. It shows why dual field interferometry has become the key technique for faint companions. Taking the exemple of the HD 95086 b exoplanet, we show how dual field interferomtry can detect an exoplanet as faint as magnitude 19.5, and how its astrometry was extracted. Use this example this paper explains how and why an astrometric accuracy of 10μas is possible, and describes the remaining biases that can hinder this measurement. Last, we conclude by presenting the orbital trajectory of 10 exoplanets in 4 systems, and conclude with the short and longer term perspectives of the technique.

Reçu le :
Accepté le :
Première publication :
DOI : 10.5802/crphys.144
Keywords: Astrometry, Exoplanets, Direct detection, Interferometry, High angular resolution
Mot clés : Astrométrie, Exoplanètes, Détection directe, Interferométrie, Haute résolution angulaire
Sylvestre Lacour 1

1 LESIA, Observatoire de Paris, Université PSL, CNRS, Université Paris Cité, Sorbonne Université, 5 place Jules Janssen, 92195 Meudon, France
Licence : CC-BY 4.0
Droits d'auteur : Les auteurs conservent leurs droits 
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     title = {Astrometry of directly imaged exoplanets with optical interferometry},
     journal = {Comptes Rendus. Physique},
     publisher = {Acad\'emie des sciences, Paris},
     year = {2023},
     doi = {10.5802/crphys.144},
     language = {en},
     note = {Online first},
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Sylvestre Lacour. Astrometry of directly imaged exoplanets with optical interferometry. Comptes Rendus. Physique, Online first (2023), pp. 1-14. doi : 10.5802/crphys.144.

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