Ge/Ay133

1. What can transit observations tell us about (exo)-planetary science? Part II – “Spectroscopy” & Atmospheric Composition/Dynamics Kudos to Heather Knutson, now at Caltech! Ge/Ay133

2. Rapid Progress: Transiting Planets, 1 May 2007

3. Ice/Rock Planets One year later (2008): 43 Systems And Counting

4. Updates from exoplanets.org :

5. Hot Jupiter/Neptune atmospheres?

6. M L T In the optical/near-IR, the spectra of M → T dwarfs (similar temp. as the hot Jupiters) show strong alkali metal lines:

7. Transiting Planets as a Tool for Studying Exoplanet Atmospheres Secondary Eclipse See thermal radiation and reflected light from planet disappear and reappear Orbital Phase Variations Transit See cyclical variations in brightness of planet See radiation from star transmitted through the planet’s atmosphere

8. Characterizing Atmospheres With Transmission Spectroscopy Star • Probes composition of atmosphere at day-night terminator • Can search for clouds, hazes, condensates Planet Atmosphere HST STIS transits of HD 209458b from 290-1030 nm (Knutson et al. 2007a)

9. First detection of an extrasolar planet atmosphere: Look for the transit depth in filters on and off the Na D-line with HST. Charbonneau, D. et al. 2001, ApJ, 568, 377

10. Vidal-Madjar, A. et al. 2004, ApJ, 604, L69 Atmospheres Part II: Most atoms have their so called resonance lines in the UV. The H I depth is VERY large. EXOSPHERE?

11. Water and Haze on HD 189733b Featureless visible light spectrum indicates hazes… … which disappear in infrared, revealing water absorption features. Figure from Swain et al (2008) showing infrared atmospheric transmission function derived from HST NICMOS spectra compared to models for the planet’s transmission spectrum with (orange) and without (blue) additional methane absorption (Tinetti et al. 2008). Figure from Pont, Knutson et al. (2007) showing atmospheric transmission function derived from HST ACS measurements between 600-1000 nm

12. What about day/night chemistry? Need IR observations: GL 229B (BD) Oppenheimer, B. et al. 1998, ApJ, 502, 932 T dwarf IR opacities dominated by CH4, H2O.

13. Use secondary eclipses to acquire dayside fluxes: A Broadband Emission Spectrum For HD 189733b Charbonneau, Knutson et al. (2008), Barman (2008)

14. Can even collect R~50-100 spectra: IRS Data for HD 189733b Grillmair et al., Nature 456, 767 (Dec. 11 2008) Gillett, Low, & Stein (1969), “The 2.8-14 Micron Spectrum of Jupiter” “Most of the features of the 2.8-14 μm spectrum of Jupiter can be accounted for on the basis of absorption by NH3, CH4, and H2.”

15. A Near-IR Emission Spectrum for HD 189733b HST NICMOS observations of a secondary eclipse of HD 189733b “Most of the features of the 2.8-14 μm spectrum of Jupiter can be accounted for on the basis of absorption by NH3, CH4, and H2.” Swain et al. (2009)

16. Even in space, these measurements are at the limits of current detectors: HST NICMOS Spitzer

17. A Surprise: The Emission Spectrum of HD 209458b Requires a model with a temperature inversion and water features in emission instead of absorption. Knutson et al. (2008c), Burrows et al. (2007) Why would two hot Jupiters with similar masses, radii, compositions, and temperatures have such different pressure-temperature profiles?

18. Gas Phase TiO/VOTemperature Inversion?Problem: Cold Trap TrES-4 is a great test case! Teq = 1760 K One alternative: photochemistry (tholins, polyacetylenes?) Inverted As described in Hubeny et al. (2003), Burrows et al. (2007, 2008), and Fortney et al. (2008) Non-Inverted Figure from Fortney et al. (2008)

19. Possible Explanation: UV Chromospheric Stellar Activity? Increasing UV Figure from Knutson et al. 2010, ApJ, 720, 1569

20. Ultimately want many objects/wavelengths; Solution: Use 3.6 and 4.5 μm phase curves to map extent of inversion Problem: Switch from inverted to non-inverted states can artificially increase day-night contrast Model for HD 209458b from Showman et al. (2008) Observations of HD 209458b from Knutson et al. (2008a)

21. Ultimately want many objects/wavelengths; Solution: Use 3.6 and 4.5 μm phase curves to map extent of inversion Test of Spitzer color index with stellar UV activity Knutson et al. 2010, ApJ, 720, 1569 Observations of HD 209458b from Knutson et al. (2008a) The warm Spitzer mission has done another 18 planets at 3.6/4.5 mm (H. Knutson, P.I.).

22. Ground? Line shape would give pressure at the photosphere, center/shift the wind profiles. Challenge is the Earth’s atmosphere! Terrestrial CH4 CO Search Limits only just beginning to reach sufficient sensitivity… Deming, D. et al. 2005, ApJ, 622, 1149

23. First possible ground based high spectral resolution detection: Gives orbital velocity and thus absolute mass of the planet & star (w/RV), is the blueshift due to strong winds across the terminator? Snellen, I. et al. 2010, Nature, 465, 1049

24. A Diversity of Worlds Super-Earths & Mini-Neptunes Mass range: 1-10 Earth masses

25. Prospects for Studies of Terrestrial Planets With the James Webb Space Telescope (launches 2018?) Predicted transmission spectrum for a 0.5 Mearth, 1 Rearth, 300 K planet orbiting a M3V, J=8 star Neptune-mass planets are observable with Spitzer and HST…. … but observations of earth-like planets orbiting M dwarfs will require JWST-level precision Seager, Deming, & Valenti (2008)

26. Imaging extrasolar planetary systems? Marois et al. (2008), Science Jovian-mass planets cool slowly, so few-few 10s of MYr old objects are fairly bright… And have emission peaks in the near-IR atmospheric windows where AO systems perform well.

27. Signatures of “young” planetary systems? One group of systems to try are the so-called ‘debris disks’ that we’ll learn about later. These are young stars with “2nd generation dust” caused by planetesimal collisions. HR 8799 Marois et al. (2008), Science • Pictoris (VLT, • proper motion • now confirmed)

28. Can also use coronography/PSF subtraction in space: Too bright @ 600 nm? Circum- planetary disk? If so, Mp? Use dynamics!

29. Modeling of the dust ring suggests an upper limit to the companion of ~3 MJ. Photometry-based mass estimate uncertainties are dominated by possible age(s). Formation? (In situ/scattering?) Fomalhaut dynamical analysis of companion mass: Kalas, P. et al. (2008), Science Neptune-mass planets are observable with Spitzer and HST….