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