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1、Extrasolar Planets.I.,What do we know and how do we know it.Basic planetary atmospheresSuccessful observations and future plans,Planets Orbiting Other Stars,Total:209 discovered to-date.Statistics:Gas giant planets,like Jupiter Beaulieu et al.2006).No Earth-like planets yet,Planets Orbiting Other St
2、ars:,after Gould et al.(2006),First Super-Earth discovered GJ 876d:-Mass 7.5 EarthsAlso HD 69830b:-Mass 10 Earths,NASA Kepler mission:Radii in this range,M=MercuryV=VenusE=Earth,etc.,Atmosphere:,In general-outer boundary for planets thermal evolution-the extrasolar planets have introduced conditions
3、 never imaginedClouds&(photo)chemistryEvaporation(very hot&hot Jupiters)Transits allow spectroscopic studies of the planets atmosphere,The Close-in Extrasolar Giant Planets,Type and size of condensate is important Possibly large reflected light in the optical Thermal emission in the infrared,Seager&
4、Sasselov 2000,Atmosphere:,What is special about atomic Na and the alkali metals?,Seager&Sasselov(2000),Atmosphere:,Theoretical Transmission Spectra of HD 209458 b,Wavelength(nm),Occulted Area(%),Seager&Sasselov(2000),Transmission Spectra,H=kT/gmH scale height sl extinction cross section L path lengt
5、h,How large is the planet atmospheresignal?It depends on theatmosphere annulus/star area,Atmosphere:,The tricks of transmission spectroscopy:,Brown(2001),The actual detection(with the HST):a 5s signal2x weaker than model expected,but within errorsMight indicate high clouds above terminator,Charbonne
6、au et al.(2002),planet/star flux ratio is:,Star,Planet,Earth,Reflected Light,p is albedo,Atmospheric Probe,Sudarsky Planet typesI:Ammonia CloudsII:Water CloudsIII:ClearIV:Alkali MetalV:Silicate CloudsPredicted Albedos:IV:0.03V:0.50,Sudarsky et al.2000,Picture of class IV planet generated using Celes
7、tia Software,Photometric Light Curves,Micromagnitude variability from planet phase changes Space-based:MOST(2005),COROT(2007),Kepler(2008),D m=2.5(Rp/D)22/3/p(sin(a)+(p-a)cos(a),Seager et al.2000,Scattered Light,Need to consider:phase function multiple scattering,Scattered Light Changes with Phase,S
8、eager,Whitney,&Sasselov 2000,51 Peg 550 nm,Mission,Microvariability and Oscillations of STars/Microvariabilit et Oscillations STellaire First space satellite dedicated to stellar seismology Small optical telescope&ultraprecise photometer goal:few ppm=few micromag,MOST at a glance,Canadian Space Agen
9、cy(CSA),circular polar orbit altitude h=820 km period P=101 min inclination i=98.6 Sun-synchronous stays over terminator CVZ 54 wide-18 Decl.+36 stars visible for up to 8 wks Ground station network Toronto,Vancouver,Vienna,MOST at a glance,Orbit,Lightcurve Model for HD 209458b,Relative depthstransit
10、:2%eclipse:0.005%Duration3 hoursPhase changes of planet,Phase,Relative Flux,Eclipse,Transit,The Lightcurve from MOST,45 days,0.03 mag,2004 data:14 days,4 orbital cycles 2005 data:45 days,12 orbital cyclesduty cycle:90%473 896 observations3 mmag point-to-point precision,2005 observations,40 minute bi
11、nned data,Albedo Results,Best fit parameters:Albedo:0.07 0.05stellar radius:1.346 0.005 RJupOther Parameters:stellar mass:1.101 Msuninclination:86.929period:3.52.days see Knutson et al.2006,Geometric Albedo,Radius(Jupiter),1,2,3 sigmaerror contours,Rowe et al.(in prep),0.1 mag,0.02 mag,0.8 mmag,Atmo
12、spheres,MOST bandpass,Geometric Albedo,HD 209458b is darker than Jupiter Rule out class V planet with bright reflection silicon clouds,Marley et al.1999,HD 209458b Albedos,New upperlimit on Ag,Rowe et al.(2006),(Rowe et al.2007),Models Constraints,2004 1 sigma limit or-2005 3 sigma limit,Spitzer Lim
13、it,Different atmospheres,blackbody,model,Rowe et al.2006Rowe et al.(in prep),best fit,Equilibrium Temperature,Direct Spectrophotometry,Proposed NASA Mission Nulling coronograph Can image Jupiter-like planets in Earth-like orbits,Direct Spectrophotometry,Could observe changing cloud cover and atmospheric conditions on gas giant planets with highly eccentric orbits,like HD 168443.Very exciting unique opportunity to study rates for photochemistry&forcing.,Some of the Hot Jupiters do not match wellmodels based on Jupiter&Saturn:,More diversity than expected?.,Gaudi(2005)and Burrows et al.(2003),
