April 3rd 2018 -- EWASS – Liverpool
Characterizing Proxima b with a
mid-infrared nulling spectrograph
D. Defrère
A. Léger, O. Absil, A. Garcia Munoz, J.L. Grenfell, M. Godolt, J. Loicq, J. Kammerer, S. Quanz, H. Rauer, L. Schifano, and F. Tian
The observing challenge
The observing challenge
Challenges for direct imaging
1. Contrast: need advanced wavefront and/or phase control techniques 2. Angular resolution: need large telescopes (or baselines)
3. Sensitivity: need large collecting area
10 100 1000
Angular separation [mas]
10-4
10-2
100
102
104
Flux at 10 microns [mJy]
10 100 1000
Angular separation [mas]
10-4
10-2
100
102
104
Flux at 10 microns [mJy]
: F stars : G stars : K stars : M stars Sp ac e nu lle r wi th 100 -m ba se lin e LB TI n ul le r EL T/ M ET IS JW ST /M IR I VL T/ VI SI R G starsF stars K stars M stars
The observing challenge
Proxima b
1. Contrast: favorable (M-type hosts star) 2. Angular resolution: very tight (~30mas)
3. Sensitivity: “favorable” as nearest rocky exoplanet
phase angle 150° 90° 60° 30° 15° 120° wavelength (μm) planet /st ar cont ras t I J H K L wavelength (μm) planet /st ar cont ras t 5 10 15 20 25 10-4 10-5 10-6 10-7 phase angle 150° 90° 60° 30° 15° 120° Turbet et al. 2016
The observing challenge
Proxima b
1. Contrast: favorable (M-type hosts star) 2. Angular resolution: very tight (~30mas)
3. Sensitivity: “favorable” as nearest rocky exoplanet
10 100 1000
Angular separation [mas]
10-4
10-2
100
102
104
Flux at 10 microns [mJy]
10 100 1000
Angular separation [mas]
10-4
10-2
100
102
104
Flux at 10 microns [mJy]
: F stars : G stars : K stars : M stars Sp ac e nu lle r wi th 100 -m ba se lin e LB TI n ul le r EL T/ M ET IS JW ST /M IR I VL T/ VI SI R G starsF stars K stars M stars Proxima b
The solution: nulling interferometry
•
Key advantages:
•
Interferometry provides the required angular resolution
•
Nulling provides the required contrast (~10
-4already
demonstrated from the ground, Menensson et al. 2011,
Defrère et al. 2016)
Nulling interferometry
LBTI
Nulling interferometry
LBTI
The observing challenge
Detection and spectroscopy (1/2)
• Ideal target for mid-infrared interferometer.The observing challenge
Detection and spectroscopy (2/2)
O3 CO2 H2O O3 CO2 H2O H2O CO2 CH4 CH4 O3 CO2 H2O CO2 O3 CO2 H2O CO2 H2O O3 CO2 H2O O3 CO2 H2O H2O CO2 CH4 CH4 O3 CO2 H2O CO2 O3 CO2 H2O CO2 H2O
• Simulated observations (R=40, blue points) imposing a S/N of 20 on continuum detection at 10 µm (Léger et al. in prep).
The observing challenge
Detecting more Proxima planets
• Aperture diameter required to detect a given ratio of planets based
The observing challenge
What about alpha Cen?
• Aperture diameter required to detect a given ratio of planets based
on Kepler’s statistics (work in progress, L. Schifano)
