1. Reflection Spectra of Giant Planets With an Eye Towards TPF (and EPIC & ECLIPSE) Jonathan J. Fortney Mark S. Marley NASA Ames Research Center 2005 Aspen Winter Conference on Astrophysics: Planet Formation and Detection February 11, 2005

2. Burrows, et al. (2001) If TPF-C planetary system targets will be older than 1 Gyr… And if technical limitations will only allow characterization ~1-5 AU from the parent star… This constrains T eff < 400 K and gravity: 1 g Saturn - 10 g Jupiter for gas giants EGP Characterization with an Eye Towards TPF-C

3. T eff < 400 K constrains expected dominant chemical species: Carbon- CH 4 Nitrogen- NH 3 Oxygen- H 2 O Expected cloud species: H 2 O & NH 3 T-P profiles for planets in orbit around the Sun T int =400K, 1 AU T int =250K, 3 AU T int =100K, 5 AU The atmosphere code has been used extensively to model the atmospheres of brown dwarfs and solar system planets

4. Fairly good agreement with Jupiter’s profile from Galileo Entry Probe Our equilibrium chemistry ignores photochemically produced species that control the heat balance in the Jupiter’s stratosphere. Jupiter’s Atmosphere from the Galileo Entry Probe

5. TOP: CH 4 absorption coeffs. (Karkoschka,1994) BOTTOM: Normalized Flux (at 0.5 µm), Observed vs. Model with solar abunds, no tweaked parameters or hazes. Jupiter Model

6. At long “visible” wavelengths, for the hotter and younger objects, thermal radiation dominates over reflected stellar light Stellar flux is our Sun

7. TPF-C: 0.5 – 0.8 µm encompasses a very limited spectral region Signature of clouds is clear (for instance, ratio of X0/X1 filters) Longer wavelengths, to ~1.04 µm, includes thermal radiation at high T eff Standard Visible Filters: UBVRI I-band reaches to 1.04 µm X2 filter also reaches thermal radiation near T eff ~ 400 K What information can be obtained from a few filters? Are clouds and T eff detectable?

8. Color-Color Diagrams BOLD=10X Jupiter g THIN= Jupiter g X2,V,I are an excellent T eff diagnostic from 400-250K, and fair from 100- 250K. V,X0,X1 are a diagnostic for clouds. B (~0.45 µm) is better than X0, but perhaps too short in λ

9. Conclusions EGPs of ages > 1 Gyr, masses below ~ 10 M J, d > 1 AU are limited in T eff < 400K All visible spectra dominated by gaseous CH 4 absorption “Clear” (what about hazes?), H 2 O cloud dominated, and NH 3 cloud dominated, are expected (Sudarsky, et al 2000) Discerning clear from cloudy atmospheres can be done from 0.5 – 0.8 µm This can be done with low-res spectra or a few filters Determining T eff in this spectral range will be difficult Determining T eff for cloudy planets (T eff < 400K) will be greatly helped if TPF-C bandpass is extended to at least to ~1.04 µm CH 4 band depths will help gauge EGP (and perhaps the planetary system’s?) metallicity I have not yet in detail examined farther into the near IR, but that should be promising, due to the greater thermal radiation