Spectroscopy of extrasolar planets atmosphere Alain Lecavelier des Etangs Institut d’Astrophysique de Paris

Alfred Vidal-Madjar Jean-Michel Désert Roger Ferlet Guillaume Hébrard (IAP, Paris) Alain Lecavelier des Etangs Institut d’Astrophysique de Paris VLST Workshop STScI Feb. 26-27, 2004

Future is difficult to predict Spectroscopy of extrasolar planets atmosphere Future is difficult to predict In 1994, “When will the first extrasolar planet detected ? ” answers: 2000, 2010… 1 year ago: detection of OI: “not within the current capabilities” Prediction: Future is impossible to predict VLST Workshop STScI Feb. 26-27, 2004

With a VLST: (extrapolation to the future from the present) Spectroscopy of extrasolar planets atmosphere What has been done (HST): (description of the present) 4 UV detections of the bottom and upper atmosphere of HD 209458b in space, in the UV-optical wavelength range. With a VLST: (extrapolation to the future from the present) Large sample of extrasolar planets Detailed view of planets around nearby stars Toward Earth and Ocean-like planets VLST Workshop STScI Feb. 26-27, 2004

VLST Workshop STScI Feb. 26-27, 2004 Transits: a powerful and sensitive method VLST Workshop STScI Feb. 26-27, 2004

Transit of HD 209458 (Charbonneau et al. 2000) VLST Workshop STScI Feb. 26-27, 2004

Radial velocity + Occultation depth HD 209458b (Mazeh et al. 2000) Period = 3.524738 days Mass = 0.69 ±0.05 MJupiter Radius = 1.35 ±0.04 RJupiter Density = 0.35 ±0.05 g/cm3

~0.01% accuracy

VLST Workshop STScI Feb. 26-27, 2004 HD 209458b: Detection of the atmosphere in NaI (Charbonneau et al. 2002) 0.0232 ± 0.0057 % VLST Workshop STScI Feb. 26-27, 2004

Search for HI Lyman a (1216 Å) Y (slit aperture) 1214 1215 1216 1217 Wavelength (Å) VLST Workshop STScI Feb. 26-27, 2004

VLST Workshop STScI Feb. 26-27, 2004

VLST Workshop STScI Feb. 26-27, 2004 15 ±4% Flux Ratio Time (hours) Begin of transit End of transit VLST Workshop STScI Feb. 26-27, 2004

The planet is evaporating 15 ±4% Time (hours) Flux ratio -100 0 100 (km s-1) | | | Wavelength (A) Before transit During transit HD209458b (1.35 RJupiter = 96,500 km) → 1.6 % absorption Roche Lobe (2.7 Rplanet = 3.6 RJupiter) → 10 % absorption Hydrogen: 15 % absorption → 3.2 Rplanet= 4.3 RJupiter = 300 000 km → Beyond the Roche Lobe  Hydrogen is escaping Absorption width: –130 km/s to 100 km/s Vesc = 54 km/s → Beyond escape velocity  Hydrogen is escaping The planet is evaporating

Escape rate estimate How much for 15% absorption? VLST Workshop STScI Feb. 26-27, 2004

Escape rate > 1010 g/s

An extended upper atmosphere around the extrasolar planet HD209458b A. Vidal-Madjar (IAP) A. Lecavelier des Étangs (IAP) J.-M. Désert (IAP) G. E. Ballester (Univ. Arizona) R. Ferlet (IAP) G. Hébrard (IAP) M. Mayor (Obs. Genève) Nature 422, 143 (2003) VLST Workshop STScI Feb. 26-27, 2004

HST G140L Observations Oct-Nov 2003 Fig 1 VLST Workshop STScI Feb. 26-27, 2004

VLST Workshop STScI Feb. 26-27, 2004 Terrestrial airglow Stellar spectrum SiIII H I Lyman a O I C II Stellar continuum VLST Workshop STScI Feb. 26-27, 2004

Confirmation of the HI absorption HI Lyman a Fig 2a Out of transit In transit Si III ~5 % Wavelength (Å) VLST Workshop STScI Feb. 26-27, 2004

Detection of Carbon and Oxygen Vidal-Madjar et al. 2004 (astro-ph/0401457) Detection of Carbon and Oxygen Out of Transit C II In Transit O I ~13 % ±4.5 % ~8 % ±3.5 % Wavelength (Å) VLST Workshop STScI Feb. 26-27, 2004

Consequence Vidal-Madjar et al. (2004 astro-ph/0401457) Oxygen and carbon are also present in the upper atmosphere of HD 209458b They are carried out by the hydrogen flow:  HYDRODYNAMICAL ESCAPE (« BLOW-OFF ») VLST Workshop STScI Feb. 26-27, 2004

VLST Workshop STScI Feb. 26-27, 2004 More can be done Last observations must be confirmed (2.5s) Other species are likely detectable with HST Cycle 13 proposal… VLST Workshop STScI Feb. 26-27, 2004

Planets to be discovered Today ~120 planets know Rad.Vel. < 2003 10m/s (present) 1m/s (2003 HARPS) KEPLER (2007/8) Harps 2003 COROT (2006)

A large number of targets for the VLST ≥7% planet / star 15% « Hot Jupiter » / planet  1% « Hot Jupiter » / star 10% transiting planet / « Hot Jupiter »  0.1% transit / star 10,000 G stars (V≤8)  10 « Hot Jupiter » transits on stars V≤8 85,000 G stars (V≤10)  85 transits on V≤10 300,000 G stars (V≤12)  300 transits on V≤12 VLST Workshop STScI Feb. 26-27, 2004

Planets with Earth-like orbital distances For d=1AU, Probability Transit  R*/a=0.5% ~30% of known planets within 0.5-1.5 AU 0.15% 1AU-transiting planet per planetary system ~30 transiting planet on Earth-like orbit around a G-type star V≤12 (For giant planets only…) IF 25% low-mass planet/star ~30 transiting low-mass planet on Earth-like orbit around a G-type star V≤10 VLST Workshop STScI Feb. 26-27, 2004

Summary of detection capabilities on V≤8 stars HST VLST Height species FUV 4% 0.4% 10,000 km H, C, O, CO, O2 NUV 1% 0.1% 2,500 km Fe, Mg, et al.; CO, NO Bands <0.1% <0.01% <250 km O3 Opt. 0.01% 0.001% 25 km Na, K, Li, OH (3090A) NUV-Opt Time scan VLST Workshop STScI Feb. 26-27, 2004

VLST Workshop STScI Feb. 26-27, 2004 Time-scan HST observations used a total of ~100-200 minutes exposures during transits.  VLST gives diagnostics in few minutes exposure Tingress=80 (Rp/RJup) (a/1AU) ½ minutes THD209458= 22 minutes Scan of the planets “weather” during the partial occultation phases (ingress, egress): VLST Workshop STScI Feb. 26-27, 2004

Temperate Uranus (Ocean-planets) (A. Leger 2003) Scale height: H = 250 (T/300K) (Rp/REarth)2 (Mp/MEarth)-1 m km  HO2 =8 km on the Earth Uranus parameter (Rp=4REarth , Mp=15MEarth)  same scale height: HO2 =8 km  Expected occultation depth ~0.001% … Likely detectable on broad-bands. VLST Workshop STScI Feb. 26-27, 2004

VLST Workshop STScI Feb. 26-27, 2004 Scientific goals Structures of the atmosphere of extra-solar planets (composition, dust/clouds/haze content, “weather”). Interaction between planets and stars Evolution of planets atmosphere (escape, fate of remaining core..) Probe of new kinds of planets (temperate Uranus, evaporation-modified hot-Jupiters) Life ? (improve our knowledge of habitable planets) VLST Workshop STScI Feb. 26-27, 2004

VLST Workshop STScI Feb. 26-27, 2004 This picture shows also the Earth atmosphere with emission from hydrogen and oxygen at high (HST) altitude where the C/O is obviously very low. Terrestrial airglow Stellar spectrum SiIII H I Lyman a O I C II Stellar continuum VLST Workshop STScI Feb. 26-27, 2004

VLST Workshop STScI Feb. 26-27, 2004 END END VLST Workshop STScI Feb. 26-27, 2004