Interior Structure of Rocky and Vapor Worlds

Interior Structure of Rocky and Vapor Worlds Diana Valencia, 4 April 2011 NASA Sagan Fellow, MIT Exploring Strange New Worlds: From Giant Planets to Super-Earths

Super-Earths in the context of exoplanets 18 Super-Earths complete 16 the inventory of planets 14 for formation models Intermediate objects that allow for comparative planetology Radius (R Earth ) 12 10 8 6 4 H-He H-He & H2O U N S J May be habitable 2 Me Ma V E H2O & Rocks 0.1 1 10 100 1000 10000 Mass (M Earth )

Super-Earths Measured masses and radii of Super-Earths About 15% of stars have SE planets (perhaps up to 40%) Spectroscopy of Borucki, 10 super-earths

Data & Challenges Period & estimates of T eff, Age Minimum Mass -- RV surveys Radius Only -- Kepler Candidates M & R Coarse Spectroscopy Complexity in Composition Complex Dynamic Interiors Complex Atmospheres Few data points in the Solar System

Characterizing super-earths

Characterizing super-earths Are they habitable?

Characterizing super-earths What are they made of? Are they habitable?

Characterizing super-earths What are they made of? How did they form? Are they habitable?

Characterizing super-earths What are they made of? How did they form? How did they evolve? Are they habitable?

Characterizing super-earths What are they made of? How did they form? How did they evolve? What is their atmosphere like? Are they habitable?

Characterizing super-earths What are they made of? How did they form? How did they evolve? What is their atmosphere like? Are they habitable? Single Planets Population

Now we have M & R + P, T eff,age

The First Transiting super-earths CoRoT- 7b Kepler-10b 55Cnc-e GJ 1214b +0.033 Radius (RE) 1.58 ± 0.1 1.416-0.036 1.63 ± 0.16 +0.13 2.13-0.14 2.678 ± 0.13 2.27 ± 0.08 Mass(ME) 4.8 ± 0.8, 6.9 ± 1.5 8.0±1.2, 5.7 ± 2.5, 2.3 ± 1.8 7.26 ± 1.36 +1.17 4.56-1.26 8.57 ± 0.64 8.0 ± 0.7 6.55 ± 0.98 Period (j) 0.854 0.837 0.74 1.58 Age (Gy) 1.2-2.3 11.9 (± 4.5) ~ 5 3-10 Temp (K) 1800 1800 2000 393-555 Ref. Leger et al 09, Queloz et al 09, Pont et al 10, Hatzes et al 10 & 11, Boise et al 10, Ferraz-Mello et al 10 Batalha et al 2010 Winn et al 2011 Demory et al 2011 Charbonneau et al 2009, Carter et al 2011

Recipe: Internal Structure Model H-He Assume a composition H 2 O, CH 4,.. Si, O, Mg, Fe Solve structure equations (M,, P, g, T, S) Need an EQUATION OF STATE

Recipe: Internal Structure Model H-He Assume a composition H 2 O, CH 4,.. Si, O, Mg, Fe Solve structure equations (M,, P, g, T, S) Need an EQUATION OF STATE Obtain: R(M; )

Recipe: Internal Structure Model H-He Assume a composition H 2 O, CH 4,.. Si, O, Mg, Fe Solve structure equations (M,, P, g, T, S) Need an EQUATION OF STATE Obtain: R(M; ) Valencia et al 06, Fortney et al 07, Grasset et al 07, Seager et al 07, Valencia et al 10, Rogers and Seager 10, Nettlemann & Fortney 10

M=5M Maximum Radius 0 10 20 H2O 30 40 50 60 Mantle 70 80 100 90 Minimum Radius Core Super-Earth Composition M=5M 40 Maximum Radius 30 0 10 100 20 H2O Silicate 90 50 12650 80 60 (ices) Mantle 70 70 80 12000 100 90 60 11350 0 50 10 20 10650 40 30 Fixed Si/Fe ratio Late delivery of H2O 0 10 Terrestrial Side10000 40 30 50 Radius (km) 40 60 9350 20 4000 6000 8000 10000 12000 14000 16000 50 70 60 80 10 70 Minimum Radius 90 100 0 80 Terrestrial Side10000 20 30 10650 11350 Fixed Si/Fe ratio 12000 90 100 9350 12650 Fe Late delivery of H2O 0 Core There is degeneracy in 1 1 1 1 composition. Some compositions are 10 20 30 40 50 60 70 80 90 100 improbable. Valencia et al. 2007b, see also Rogers and Seager 2010

M=5M Maximum Radius 0 10 20 H2O 30 40 50 60 Mantle 70 80 100 90 Minimum Radius Core ¹ z Super-Earth Composition x ¹ ¹ M=5M 40 Maximum Radius 30 0 10 100 20 H2O 90 y Silicate 50 12650 80 60 (ices) Mantle 70 70 80 12000 100 90 60 11350 0 50 10 20 10650 40 30 Fixed Si/Fe ratio Late delivery of H2O 0 10 Terrestrial Side10000 40 30 50 Radius (km) 40 60 9350 20 4000 6000 8000 10000 12000 14000 16000 50 70 60 80 10 70 Minimum Radius 90 100 0 80 Terrestrial Side10000 20 30 10650 11350 Fixed Si/Fe ratio 12000 90 100 9350 12650 Fe Late delivery of H2O 0 Core There is degeneracy in 1 1 1 1 composition. Some compositions are 10 20 30 40 50 60 70 80 90 100 improbable. Valencia et al. 2007b, see also Rogers and Seager 2010

Earth s Structure: MANTLE Olivine + Pyroxene (Mg,Fe)2SiO4 + (Mg,Fe)2Si2O6 Perovskite + Magnesiowustite (Mg,Fe)SiO3 + (Mg,Fe)O Post - Perovskite + Magnesiowustite (Mg,Fe)SiO3 + (Mg,Fe)O Iron + alloy Fe + (S, Si, O, H, C) CORE Iron-Nickel

Earth s Structure: Fe, Mg, Si, O, Ca,Al,Ti MANTLE Olivine + Pyroxene (Mg,Fe)2SiO4 + (Mg,Fe)2Si2O6 Perovskite + Magnesiowustite (Mg,Fe)SiO3 + (Mg,Fe)O Post - Perovskite + Magnesiowustite (Mg,Fe)SiO3 + (Mg,Fe)O Iron + alloy Fe + (S, Si, O, H, C) CORE Iron-Nickel

Variety in Rocky Compositions Fe, Mg, Si, O, Ca,Al, Ti 1. The planet has an Fe/Si, Fe/Mg... inventory which depends on its formation inventory and subsequent early evolution (giant impacts + atmospheric erosion) Iron Iron-rich Earth-like no-iron (65% iron core 37 silicate mantle, no iron) (33% iron core 67 silicate mantle, 10% iron by mol) (pure Mgsilicate)

Variety in Rocky Compositions 2. Differentiated vs Undifferentiated planet silicate atmosphere R p =1.68R silicate mantle silicate Planet R cmb =0.86R M=5.6M iron solid core M=5.3M For CoRoT-7b first reported mass value Valencia et al, 2010; see also Tanton-Elkins and Seager 2009 for a mechanism for a coreless planet

Rocky Compositions U N 20000 Radius (km) 10000 8000 6000 no iron super-mercury pure-fe Earth-like 1 10 Mass (M Earth )

Rocky Compositions U N 20000 Radius (km) 10000 8000 6000 no iron super-mercury pure-fe Earth-like For a probable limit to the Fe/Si lower ratio see Marcus et al 10 1 10 Mass (M Earth )

Rocky Compositions U N 20000 Radius (km) 10000 8000 6000 no iron super-mercury pure-fe K-10b C-7b Earth-like 1 10 Mass (M Earth ) Valencia et al 2010, Valencia 2011

Rocky Compositions U N 20000 Radius (km) 10000 8000 6000 no iron super-mercury pure-fe This study, 55Cnc-e K-10b C-7b Earth-like 55Cnc-e Winn et al 11 0.35 R E 1 10 Mass (M Earth ) in Demory et al 2011

What about their envelopes? 20000 100% H 2 O Radius (km) 10000 8000 6000 50% H 2 O 20% H 2 O 5% H 2 O super-mercury pure-fe This study, 55Cnc-e K-10b C-7b 1 10 Mass (M Earth ) Earth-like 55Cnc-e Winn et al 11 T=2500 @ 10 bars Vapor Atmosphere Valencia et al, 2010, Valencia 2011, Demory et al 2011

What about their envelopes? 10% H-He U N 20000 20000 1% H-He 100% H 2 O Radius (km) 10000 8000 6000 50% H 2 O 20% H 2 O 5% H 2 O super-mercury pure-fe This study, 55Cnc-e K-10b C-7b Earth-like 55Cnc-e Winn et al 11 Radius (km) 10000 8000 6000 0.1% H-He 0.01% H-He super-mercury pure-fe This study, 55Cnc-e K-10b C-7b Earth-like 55Cnc-e Winn et al 11 T=2500 @ 10 bars T=2500 @ 10 bars 1 10 Mass (M Earth ) 1 10 Mass (M Earth ) Vapor Atmosphere H-He Atmosphere Valencia et al, 2010, Valencia 2011, Demory et al 2011

Atmospheric Erosion Energy limited calculation based on UV flux dm = 3 F EUV dt 4 G K tide = 10 11 g/s For more details on see Lammer et al 09 within an order of magnitude of the escape rate of HD 209458b Even if it has a silicate atmosphere, it is thick enough for UV absorption

What about their envelopes? 10% H-He U N 20000 20000 1% H-He 100% H 2 O Radius (km) 10000 8000 6000 50% H 2 O 20% H 2 O 5% H 2 O super-mercury pure-fe This study, 55Cnc-e K-10b C-7b 1 10 Mass (M Earth ) Earth-like 55Cnc-e Winn et al 11 Radius (km) 10000 8000 6000 0.1% H-He 0.01% H-He super-mercury pure-fe This study, 55Cnc-e Earth-like T=2500 @ 10 bars T=2500 @ 10 bars K-10b C-7b 1 10 Mass (M Earth ) 55Cnc-e Winn et al 11

191 159 127 CoRoT-7b s origin? Rocky Origin Volatile Origin 8 CMF f =0.22 222 0.1 254 318 286 b) inward migration Mass (M E ) 7 6 5 cored planet CMF f =0.33 silicate planet Corot-7b s Mass Mass [M ] 100 10 95 rocky cores 15.9 14.3 7.9 H-He planets 9.5 12.7 11.1 vapor planets 4 0 0.5 1 1.5 2 2.5 3 Time (Gyr) 1 0.01 0.1 1 10 Age[Ga] Valencia et al. 2010, see also Jackson et al 2010

191 159 127 CoRoT-7b s origin? Unconstrained Rocky Origin Volatile Origin 8 CMF f =0.22 222 0.1 254 318 286 b) inward migration Mass (M E ) 7 6 5 cored planet CMF f =0.33 silicate planet Corot-7b s Mass Mass [M ] 100 10 95 rocky cores 15.9 14.3 7.9 H-He planets 9.5 12.7 11.1 vapor planets 4 0 0.5 1 1.5 2 2.5 3 Time (Gyr) 1 0.01 0.1 1 10 Age[Ga] Valencia et al. 2010, see also Jackson et al 2010

Rocky or Vapor? 20000 pure-fe 10000 CoRoT-7b Kepler-10b 55Cnc-e Winn et al 11 super-mercury Earth-like Density (kg/m 3 ) 5000 v E Kepler-11b This study, 55Cnc-e no iron 2000 GJ 1214b N U 1000 2 4 6 8 10 12 14 16 Mass (M Earth ) in Demory et al 2011

GJ 1214b Charbonneau et al 2009 Radius = 2.678 ± 0.13 R Earth Mass = 6.55 ± 0.98 M Earth Period = 1.58 days Age = 3-10 Gy T = 393-555 K

GJ 1214b atmosphere from Miller-Ricci- Kempton et al 11 Miller-Ricci & Fortney 2010

GJ 1214b Composition Radius (km) 20000 10000 8000 6000 100% H 2 O 50% H 2 O 20% H 2 O 3% H 2 O GJ 1214b Charbonneau et al 09 super-mercury K11-b GJ 1214b Carter et al 10 K-10b C-7b 55Cnc-e (2) U 55Cnc-e (1) N Earth-like Because we expect some component of rocky material, GJ 1214b has some H-He. We calculate that H-He is present in amounts less than ~8% 1 10 Mass (M Earth ) T=1000 @ 10 bars see also Rogers and Seager 2010 Nettlemann & Fortney 2010

GJ1214b: Unfolding picture Observations at the ~ millibar level Interior models start ~ bar level low or high molecular weight atmosphere? From discovery paper: Atmosphere What is the probably has composition of the H-He nucleus? With small R (from Carter et al 11), very little room for H-He

Structure of a H 2 O vapor GJ 1214b

Transit only planets: Kepler-9d 1% H-He GJ 436b HAT-P-11 0.1% H-He GJ 1214b Uranus Neptune Kepler-4b 100% H2O 50% H2O 20% H2O 5% H2O Can constrain maximum mass & maximum amount of volatiles Terrestrial line CoRoT-7b Fe-pure line Kepler-9d in Havel et al 2011

A theorist point of view on observational strategies

A theorist point of view on observational strategies If you need to increase precision on mass or radius, choose radius If you need to decide between measuring mass or radius, choose radius Transit only, hotter planets are better constrained than cooler ones

Summary We have now a handful of hot transiting super-earths. The composition of planets reflects their initial formation inventory and secondary formation processes (i.e. giant impacts, atmospheric escape). The composition of CoRoT-7b and Kepler-10b is very similar: ironenriched (by ~3x compared to Earth) 55Cnc-e has two radius measurements that stand at the 3 sigma level. While Winn et al 2011 value suggests it belongs to the same family of CoRoT-7b and Kepler-10b, Demory et al 2011 value suggests this is a vapor planet. GJ1214b undoubtedly has a volatile envelope. The observations of the atmosphere seem to be (somewhat) conflicting about its composition. Interior models predict at most ~10% of H-He by planetary mass.

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