lain Lecavelier des Etangs tut d’Astrophysique de Paris Spectroscopy of extrasolar planets atmosphere
Mar 09, 2016
Alain Lecavelier des EtangsInstitut d’Astrophysique de Paris
Spectroscopy of extrasolar planets
atmosphere
VLST Workshop STScI Feb. 26-27, 2004
Alain Lecavelier des EtangsInstitut d’Astrophysique de Paris
Alfred Vidal-MadjarJean-Michel Désert
Roger FerletGuillaume Hébrard
(IAP, Paris)
VLST Workshop STScI Feb. 26-27, 2004
• 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
Spectroscopy of extrasolar planets atmosphere
VLST Workshop STScI Feb. 26-27, 2004
• What has been done (HST): (description of the present)
4 UV detections of the bottom and upper atmosphere of HD 209458bin 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
Spectroscopy of extrasolar planets atmosphere
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)
Radial velocity + Occultation depthRadial velocity + Occultation depth
Period = 3.524738 daysPeriod = 3.524738 days
Mass = 0.69 ±0.05 MMass = 0.69 ±0.05 MJupiterJupiter
Radius = 1.35 ±0.04 RRadius = 1.35 ±0.04 RJupiterJupiter
DensityDensity = 0.35 ±0.05 g/cm= 0.35 ±0.05 g/cm33
HD 209458bHD 209458b(Mazeh et al. 2000)
~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 (1216 Å)
1214 1215 1216 1217
Wavelength (Å)
Y (s
lit a
pertu
re)
VLST Workshop STScI Feb. 26-27, 2004
VLST Workshop STScI Feb. 26-27, 2004
15 ±4%
Flux
Rat
io
Time (hours)
Beg
in o
f tra
nsit
End
of tr
ansi
t
• 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
15 ±4%
Time (hours)
Flux
ra
tio-100 0 100 (km s-1) | | |
Wavelength (A)
Beforetransit
Duringtransit
VLST Workshop STScI Feb. 26-27, 2004
Escape rate estimateHow much for 15% absorption?
Escape rate > 1010 g/s
VLST Workshop STScI Feb. 26-27, 2004
An extended upper atmospherearound 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 ObservationsOct-Nov 2003
• Fig 1
VLST Workshop STScI Feb. 26-27, 2004
Terrestrial airglow
SiIII O IH I Lyman C II
Stellar spectrum
Stellar continuum
VLST Workshop STScI Feb. 26-27, 2004
Confirmation of the HI absorption
• Fig 2a
Wavelength (Å)
Out of transitIn transit
Si III
HI Lyman
~5 %
VLST Workshop STScI Feb. 26-27, 2004
Vidal-Madjar et al. 2004 (astro-ph/0401457)
Detection of Carbon and Oxygen
Wavelength (Å)
Out of TransitIn Transit
O I
C II
~13 %±4.5 %
~8 %±3.5 %
VLST Workshop STScI Feb. 26-27, 2004
ConsequenceVidal-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
• Last observations must be confirmed (2.5• Other species are likely detectable with HST
Cycle 13 proposal…
More can be done
Planets to be discovered
10m/s(present)1m/s(2003HARPS)
10-5
0.0001
0.001
0.01
0.1
1
10
100
0.01 0.1 1 10 100
SS msini (Jup)pulsar
m sin i
a (au)
Today ~120 planets know
COROT (2006)COROT (2006)
KEPLERKEPLER(2007/8)(2007/8)
Rad.Vel.< 2003Harps2003
VLST Workshop STScI Feb. 26-27, 2004
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 speciesFUV 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
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 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
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
This picture shows also the Earth atmosphere with emission from hydrogen and oxygen at high (HST) altitudewhere the C/O is obviously very low.
Terrestrial airglow
SiIII O IH I Lyman C II
Stellar spectrum
Stellar continuum
VLST Workshop STScI Feb. 26-27, 2004
• END
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