Ge/Ay133
What (exo)-planetary science can be done with transits and microlensing?
A Jupiter transit across the Sun is ~1%:
Curvature?
Limb Darkening and Transit Profiles:
• Probes composition of atmosphere at day-night terminator
• Can search for clouds, hazes, condensates
HST STIS transits of HD 209458b from 290-1030 nm (Knutson et al. 2007a)
Atmosphere
Star
Planet
Sometimes the absence of signal is interesting:
No transits in 47 Tuc, `expectation’=30-40 (34,000 stars)
Gilliland, R.L. et al. 2000, ApJ, 545, L47
Transits, approach #1:
Search for transits in systems known to have planets at the doppler crossings.
Sato, B. et al. 2005, ApJ, astro-ph/0507009
Transits and the Rossiter-McLaughlin effect (1924):
Winn, J.N. et al. 2005, ApJ, 631, 1215
Photometry can be straightforward: Amateur observations of HD 209458 b
Bruce L. Gary, Santa Barbara, CA
Arto Oksanen
SBIG cameras, Meade telescopes, V filters
Transits, approach #2:
Search for transits in many stars using a suite of low cost robotic telescopes.
TrES-1
Alonso, R. et al. 2004, ApJ, 613, L153
Photometry from space can be extremely good:
HD 209458 - HST
The KEPLER mission is dedicated to photometry and can search for earth mass planets in the so- called habitable zone.
Brown, T.M. et al. 2001, ApJ, 552, 699
www.kepler.arc.nasa.gov
95 Mpixel camera, 115 deg2 FOV, 4’’ pixels
But ground-based work is making strides!
HD 209458 - HST
At this level of performance (0.47 milli-mag) the transits of hot Neptunes are detectable & transit timing can put stringent limits on perturbing planets into the Earth mass range.
Brown, T.M. et al. 2001, ApJ, 552, 699
Secondary eclipses canalso put limits on the visiblealbedo. The MOSTsatellite findsA(HD209458b)<0.25 (1) (Jupiter=0.5, 300-700 nm). Why so dark?
Rowe, J.F.. et al. 2006, ApJ, 646, 1241
Transit photometry from space: Kepler
A comparison of transiting planet systems:
As we’ll see, size is not a strong function of mass, so very accurate measurements are needed!
T = 1060 ± 50 KA = 0.31 ± 0.14
Secondaryecplises in the IR with Spitzer, see photons from the hot Jupiters!
Charbonneau, D. et al. 2005, ApJ, 626, 523
T = 1060 ± 50 KA = 0.31 ± 0.14
Charbonneau, D. et al. 2005, ApJ, 626, 523
Rapid Pace of Spitzer Transit Results: HD 189733b
Mapping the temperature variation of a hot Jupiter…
•T(max)~1200 K, T(min)~970 K•Hot spot ~30 ± 10° from the sub-stellar point•Bond albedo~0.30•Must be reasonably efficient circulation from day to night side.
Other routes to Earth-like planets?
Microlensing example:
Microlensing example:
Are there Earth-like planets beyond the snow-line?
Rapid Progress: Transiting Planets, 1 May 2007
One year later (2008): 43 Systems And Counting
Ice/Rock Planets
HD 149026
Other Correlations:
Why would the mass/gravity of a close-in planet be tied to the period?
May be some tie to the mass of the star…
B. Hansen & T. Barman 2007, ApJ, 671, 61
Other Correlations II:
For a given Teq (not strictly distance since the spectral type varies…), two classes of planets versus Safronov number?
B. Hansen & T. Barman 2007, ApJ, 671, 61
Seems also to be tied to the mass of the planets:
•Selection bias or poor stellar radii? X•Redistribution of energy? More next time…•Evaporation? X (if “hot start”)•Tidal heating?•Planetesimals & migration (tie to Safronov #)?
Need composition(s)!B. Hansen & T. Barman 2007, ApJ, 671, 61