Category Archives: exoplanet

Kernel-phase in space

This week, the results of the proposal selection for the Cycle 1 General Observers (GO) program with JWST were announced. In total, some 6000 hours of observing time were awarded to a large number of programs. The details of the GO program can be found on the dedicated STScI webpage.

All of that is great news on its own: the community has been waiting for JWST for a while now and now everybody is really getting ready to do the first observations with this amazing observing facility… but the reason I bring this up here is because, of all of these programs, it turns out that three are directly relevant to what we do in the context of the KERNEL project… and have the word “kernel-phase” in their title!

Two of these programs have been awarded their own time.

The first one is called “Multiplicity Survey of 20 Y Dwarfs with NIRCam Kernel Phase Interferometry“. It is a program led by Loïc Albert (Université de Montreal) that greatly benefited from the paper we published in 2019. As a result, no less than 38.8 hours of observing time were awarded to this program, that will use the kernel-phase technique, combined with the detection algorithm outlined in the paper to look for companions around a sample of 20 very cool sub-stellar objects known as Y-dwarfs. Our team will naturally contribute to the analysis of the data, using the kernel-phase pipeline developed over the course of the KERNEL project.

The second project is called “High resolution, high contrast kernel phase imaging with NIRCam“. It is a smaller program of 4.3 hours of observing time, led by Jens Kammerer, a recent PhD graduate (co-supervised by me) who recently joined STScI. Here, the plan is to target one specific object (HIP 75056 A), known to host a 20-30 Jupiter mass brown dwarf companion to fine tune the kernel-phase analysis procedures.

And an archival proposal… already?!

I was also surprised to discover that, although no data obviously already exists, there is already an archival research proposal called “Kernel-Phase Detection Limits for Planet Discovery with JWST” that was awarded to Samuel Factor, from the University of Texas.

Kernel-phase: a new standard?

To see three different projects directly bear the name “kernel-phase” in their title for the first observing programs by one of the most important observing facilities of the decade to come is a very nice thing to witness! To think that out of the 6000 hours of GO time, more than 40 (not even accounting for the commissioning) aim to take full advantage of kernel-phase is humbling.

I guess after having been a very unusual and marginal observing technique for over a decade, the idea is finally making its way through the brains of observers… who see it as a valid alternative to sparse aperture masking interferometry, particularly onboard a space borne telescope. This means that we have approximately one year to make sure that our pipeline and our detection procedures are razor sharp and ready to be used the moment the data becomes available!

KERNEL-Nuller: vidéo explicative

Il y maintenant bientôt deux ans, j’annonçais sur ce site l’acceptation d’un article publié avec mon collègue Mike Ireland présentant un mode d’observation interférométrique haut contraste robuste aux petites erreurs de correction par un suiveur de franges: le kernel-nuller.

Notre équipe à Nice est, en collaborant avec l’entreprise Bright Photonics en train de faire fabriquer un premier prototype de kernel-nuller, sous forme de composant d’optique intégrée. La situation sanitaire du COVID-19 complique un peu le calendrier de cette activité et de la thèse de doctorat qui y est liée, mais nous devrions pouvoir annoncer cette année, des résultats partiels d’une première intégration d’un tel composant sur un banc optique.

En attendant de voir ce composant en action, voici une vidéo mise en ligne il y a quelques jours, expliquant ce qui distingue le kernel-nuller du nuller interférométrique initialement imaginé par Ronald Bracewell à la fin des années 1970… et illustre comment le concept fonctionne!

Kernel-nulling talk in Grenoble

These are the slides of a presentation given on March 8, 2018 at IPAG, where I present research activities related to the KERNEL project, in particular the most recent development concerning the idea of kernel-nulling interferometry.

Predicted contrast detection limits for the L-band VIKiNG instrument concept proposed by Martinache & Ireland.

You can access the presentation file directly here.

Kernel-nulling for a robust direct interferometric detection of extrasolar planets

A new paper posted on arxiv by Frantz Martinache & Mike Ireland.


Combining the resolving power of long-baseline interferometry with the high-dynamic range capability of nulling still remains the only technique that can directly sense the presence of structures in the innermost regions of extrasolar planetary systems. Ultimately, the performance of any nuller architecture is constrained by the partial resolution of the on-axis star whose light it attempts to cancel out, and the design of nullers focuses on increasing the order of the extinction to reduce the sensitivity to this effect. However from the ground, the effective performance of nulling is dominated by residual time-varying instrumental phase errors that keep the instrument off the null. This is similar to what happens with high-contrast imaging, and is what we aim to ameliorate. We introduce a modified nuller architecture that enables the extraction of information that is robust against piston excursions. Our method generalizes the concept of kernel, now applied to the outputs of the modified nuller so as to make them robust to second order pupil phase error. We present the general method to determine these kernel-outputs and highlight the benefits of this novel approach. We present the properties of VIKiNG: the VLTI Infrared Kernel NullinG, an instrument concept within the Hi-5 framework for the 4-UT VLTI infrastructure that takes advantage of the proposed architecture, to produce three self-calibrating nulled outputs. Stabilized by a fringe-tracker that would bring piston-excursions down to 50 nm, this instrument would be able to directly detect more than a dozen extrasolar planets so-far detected by radial velocity only, as well as many hot transiting planets and a significant number of very young exoplanets.

Transit photométrique


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Simulation du transit d’une exoplanète

Cette page propose une simulation numérique du phénomène de transit photométrique d’une planète extrasolaire. Les contrôles de l’expérience, permettent tour à tour de changer:

  • Le diamètre apparent de la planète (en fraction de diamètre de l’étoile). Ex: une valeur de 0.5 veut dire que la planète a un diamètre apparent qui est la moitié de celui de l’étoile.
  • L’inclinaison de l’orbite (en degrés), variant de 0 (système observé par la tranche) à 90 degrés (système vu par les pôles).
  • Le niveau de bruit de la mesure photométrique, exprimé en pourcentage sur la valeur de référence (100%). Une valeur de 0 signifie que les mesures sont parfaites. Le bruit est simulé suivant une distribution gaussienne.

Le cadran de droite permet de visualiser le système: l’étoile, la planète et l’orbite de la planète (circulaire, en blanc) autour de l’étoile. La partie basse affiche la courbe de lumière du système pour les paramètres sélectionnés. Dans le cadran de droite, l’utilisateur peut, en cliquant sur la planète et en la promenant le long de son orbite, relier les différentes parties de la courbe de lumière à la position instantanée de la planète, grâce à la marque jaune superposée à la courbe. Il peut aussi utiliser le slider “position de la planète”.



Mode haute sensibilité

Position de la planète

Diamètre de la planète
(x diamètre étoile)
Inclinaison de l’orbite
Niveau de bruit