View
36
Download
6
Category
Preview:
DESCRIPTION
Hot Jupiter in a Tube. 0.5 m. Mirror. Mirror. Detector. HR mirror. HR mirror. Source. Sulfur discharge. Numerical solution of laser rate equations for quantum cascade laser with weak intracavity absorption line shows feasibility of detecting molecular absorption at level of 10 -6 Torr. - PowerPoint PPT Presentation
Citation preview
Hot Jupiter in a Tube R. E. Peale, J. Arnold, P. FigueiredoF. Rezaie, J. Harrington, K. Stevenson
Laboratory emission spectroscopy of simulated hot Jupiters •Hypothesis: Mimic exoplanet physical conditions to obtain lab spectra for interpreting observations.•Alternative to modeling based on lab/theory line parameters and assumptions about composition and equilibrium. Approach•Emission spectra from equilibrium and non-equilibrium mixtures•Pressure and temperature gradients.•Furnace and microwave discharge •Fourier transform spectrometer (UV to far-IR)
Significance •Emission spectra of exoplanets are known from emergent flux method.•Exoplanet molecular bands can appear as emission, in contrast to usual absorption for stars.•Non-equilibrium chemistry likely for hot Jupiters
101
103
105
500
10001500
20002500
1E-9
1E-6
1E-3
1
Fra
ctio
n o
f ca
rbo
n in
CO
Equilibrium case [Cooper and Showman 2006]. Assumes specific
reaction pathway.
10-3 10-2 10-1 100 101
100
101
102
103
104
105
P1/P
2
Average pressure (bar)
0.1 0.2 0.5 1.0 2.0
Tube diameter (cm)
Equilibrium, in furnace•Isobaric (1 mbar – 10 bar)•Isothermal (600 – 1800 K)
Disequilibrium chemistry in a furnace•For pressures relevant to observations, CO/CH4 interconversion is slow [Cooper and Showman 2006]•Assumes particular reaction pathway•Possible to observe interconversion and non-equilibrium spectra on convenient laboratory time scales.
Observations along column with pressure and temperature gradients
Sulfur discharge
Disequilibrium, in microwave discharge•Ionization•Reactive fragments•High temperatures
Common assumptions in modeling exo-atmospheres•Solar abundances•Amount of O sequestered in rock •Metals and other compounds contributed by meteorites and comets
Possible sources of spectral interferences•Opacity from photochemical haze or silicate clouds•TiO, VO, and sulfur•silicate minerals such as perovskiite and enstatite•Hydrogen and its ions •alkali metals Na and K•Fe, Mg, Ca, Al•metal hydrides FeH•Water, N2, CO2, NH3•ethylene (C2H4), acetylene (C2H2), and hydrogen cyanide (HCN)
G. Medhi, A.V. Muravjov, H. Saxena, J.W. Cleary, C.J. Fredricksen, R.E. Peale, Oliver Edwards
Hyperdog: Planetary sniffer
Source
Detector
HR mirror
HR mirror
0.5 m
Ultratrace gas detection requires long folded path
Active cavity can achieveEffective Path length > 1km
Passive cavity: Effective pathlength <100m
Mirror Mirror
QCL
HR Mirrors
Movable Mirror
Detector
Enabling technologies•External Cavity Quantum Cascade Laser•Scanning Fabry-Perot spectrometer
1035 1050 1065 1080 1095
0
1
2
3
4
5
6
7
8
Inte
nsity
x 1
03
(arb
.uni
t)
Wavenumber (cm-1)
8.1 μm QCL From Maxion
To Spectrometer
HR AR
Spherical mirror
Particular caseCH4 CO in mixtures with water vapor and carrier gases H2 and HeRelevance: hot Neptune GJ 436b with 7000-fold methane deficiency [Stevenson, Harrington et al 2010].
Reasons for chemical dis-equilibrium in exoplanets• Dynamic mixing may be faster than chemical reactions; • Photo-dissociation elevates photochemical products above
equilibrium levels; • No chemical equilibrium for HD 209458b in 1-1000 mbar range
[Copper and Showman 2006]
Spectrom eter
A bsorption Em issionG ain M edium
Mirror Mirror
A bsorption Em ission
100 101 102 103 1040.0
0.2
0.4
0.6
0.8
1.0
10-3
Torr10-5 Torr
Tra
nsm
ittan
ce (
Arb
. un
it)
Number of reflections needed
R = 97% R = 98% R = 99%
Numerical solution of laser rate equations for quantum cascade laser with weak intracavity absorption line shows feasibility of detecting molecular absorption at level of 10-6 Torr
1500
2000
2500
102
104
106
10 1 0.1CO
/CH
4 inte
rco
nve
rsio
n ti
me
(s)
P (bar)
T (K)
0
100
200
6000 8000 10000 12000 14000
0
100
200
Inte
nsi
ty
PF0040He+AirMicrowaves 32WP: 1 Torr
2 1.8 1.6 1.4 1.2 1 0.8Wavelength (micron)
Wavenumber (cm-1)
PF0042He+AcetoneMicrowaves 50WP: 1.5 Torr
He InSb detQuartz BSRes: 1.5
500 1000 1500 2000 2500 3000 3500 40000
100
200
300
400
500
600
700
PF0060Air
Inte
nsi
ty
Wavenumber (cm-1)
PF0062Air + Dry iceres = 1
BS: KBrdet:MCT
2016 12 8 4Wavelength (micron)
Spitzer bands
2300 2320 2340 2360 2380 24000
1000
2000
3000
4000
5000
FR0002Air
Inte
nsi
ty
Wavenumber (cm-1)
FR0004Air + Dry ice
Res=0.25, BS=KBr, Det=InSb
4.34 4.32 4.3 4.28 4.26 4.24 4.22 4.2 4.18
Wavelength (micron
Ultra long paths impossible due to reflection losses
www.physics.ucf.edu
QCL with broad multimode emission
External cavity with dense mode spectrum
High resolution Fabry Perot spectrometer
Application to solar system explorationDetectrion of trace gases and vapors
•Water•Hydrocarbons
Funding: Army Phase II SBIR
Steam bands
GJ436b Hot Neptune (Stevenson, Harrington et al. 2010)Observational facts InterpretationNo 1.4 micron water absorption low water?Strong 3.6 micron emission low CH4 absorptionWeak 4.5 micron emission high absorption by CO/CO2Modest 5.8 micron emission Little hot H2O emissionModest 8.0 micron emission Little hot CH4 emissionStrong 16 micron emission weak CO2 absorption
ConclusionsCO dominates IR active moleculesMuch less CH4 than expected from equilibrium model
•Strong vertical mixing to give non-equilibrium distribution•CH4 polymerization -> (e.g.) C2H2
Recommended