太阳系以外的行星.ppt

1、 extrasolar planets.i.what do we know and how do we know it.basic planetary atmospheressuccessful observations and future plansplanets orbiting other stars total: 209 discovered to-date. statistics: gas giant planets, like jupiter & saturn, exist around 12% of stars (marcy et al. 2005); lower-ma

2、ss planets (super-earths, 3 known to-date) are significantly more common (rivera et al. 2005; beaulieu et al. 2006). no earth-like planets yetplanets orbiting other stars: after gould et al. (2006)first super-earth discovered gj 876d:- mass 7.5 earthsalso hd 69830b:- mass 10 earthsnasa kepler missio

3、n: radii in this rangem = mercuryv = venuse = earth, etc.atmosphere:in general - outer boundary for planets thermal evolution - the extrasolar planets have introduced conditions never imaginedclouds & (photo)chemistryevaporation (very hot & hot jupiters) transits allow spectroscopic studies

4、of the planets atmospherethe close-in extrasolar giant planetsmacintosh pictim age form atis not supported type and size of condensate is important possibly large reflected light in the optical thermal emission in the infraredseager & sasselov 2000atmosphere:what is special about atomic na and t

5、he alkali metals?seager & sasselov (2000)macintosh pictimage formatis not supportedatmosphere: theoretical transmission spectra of hd 209458 bm a c in to s h p ic tim a g e fo rm a tis n o t s u p p o rte dwavelength (nm)occulted area (%)seager & sasselov (2000)transmission spectram acintosh

6、 pictim age form atis not supportedm a c in to s h p ic tim a g e fo rm a tis n o t s u p p o rte dh = kt/gmh scale height s sl l extinction cross section l path lengthhow large is the planet atmospheresignal? it depends on theatmosphere annulus / star aream a c i n t o s h p i c ti ma g e f o r ma

7、ti s n o t s u p p o r t e datmosphere: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 terminatorcharbonneau et al. (2002)planet/star flux ratio is:ad m acintosh pictim

8、 age form atis not supportedrpstarplanetearthm a c in to s h p ic tim a g e fo r m a tis n o t s u p p o r te dreflected lightp is albedoatmospheric probesudarsky planet typesi : ammonia cloudsii : water cloudsiii : cleariv : alkali metalv : silicate cloudspredicted albedos:iv : 0.03v : 0.50sudarsky

9、 et al. 2000picture of class iv planet generated using celestia softwarephotometric 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() + (p-)cos()m a c i n t o s h p i c ti m a g e f o r m a ti s n o t s

10、u p p o r t e dseager et al. 2000scattered light need to consider: phase function multiple scatteringscattered light changes with phase m acintosh p ic tim age form atis not supportedseager, whitney, & sasselov 200051 peg 550 nmmission q microvariability and oscillations of stars / microvariabil

11、it et oscillations stellaireq first space satellite dedicated to stellar seismology q small optical telescope & ultraprecise photometer q goal: few ppm = few micromag most at a glance canadian space agency (csa)q circular polar orbitq altitude h = 820 km q period p = 101 minq inclination i = 98.

12、6q sun-synchronousq stays over terminatorq cvz 54 wide q -18 decl. +36q stars visible for up to 8 wksq ground station networkq toronto, vancouver, vienna most at a glance mostorbit normal vectorto suncvz = continuous viewing zoneorbit lightcurve model for hd 209458brelative depthstransit: 2%eclipse:

13、 0.005%duration3 hoursphase changes of planetphaserelative fluxeclipsetransitthe lightcurve from most45 days0.03 mag 2004 data : 14 days, 4 orbital cycles 2005 data : 45 days, 12 orbital cyclesduty cycle : 90%473 896 observations3 mmag point-to-point precision2005 observations, 40 minute binned data

14、albedo resultsbest 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. 2006geometric albedoradius (jupiter)1,2,3 sigmaerror contoursrowe et al. (in prep)0.1 mag0.02 mag0.8 mmagatmospheres

15、most bandpassgeometric albedo hd 209458b is darker than jupiter rule out class v planet with bright reflection silicon cloudsmarley et al. 1999hd 209458b albedosnew upperlimit on agrowe et al.(2006)(rowe et al. 2007)models constraints2004 1 sigma limit or - 2005 3 sigma limitspitzer limitdifferent a

16、tmospheresblackbodymodelrowe et al. 2006rowe et al. (in prep)best fitequilibrium temperaturedirect spectrophotometryproposed nasa mission nulling coronograph can image jupiter-like planets in earth-like orbitsdirect 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 photoche