Transcript lec05_09oct2009

What (exo)-planetary science can be
done with transits and microlensing?
Ge/Ay133
A Jupiter transit across the Sun is ~1%:
Curvature?
Limb Darkening and Transit Profiles:
Star
Planet
Atmosphere
• 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)
Sometimes the absence of signal is interesting:
Gilliland, R.L. et al. 2000, ApJ, 545, L47
No transits in 47 Tuc, `expectation’=30-40 (34,000 stars)
Transits, approach #1:
Sato, B. et al. 2005, ApJ,
astro-ph/0507009
Search for transits in systems
known to have planets at the
doppler crossings.
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:
TrES-1
Search for transits in many
stars using a suite of low cost
robotic telescopes.
Alonso, R. et al. 2004, ApJ, 613, L153
Photometry from space can be extremely good:
Brown, T.M. et al. 2001, ApJ, 552, 699
HD 209458 - HST
The KEPLER mission is
dedicated to photometry
and can search for earth
mass planets in the socalled habitable zone.
www.kepler.arc.nasa.gov
95 Mpixel camera, 115 deg2 FOV, 4’’ pixels
But ground-based work is making strides!
Brown, T.M. et al. 2001, ApJ, 552, 699
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.
Rowe, J.F.. et al. 2006, ApJ, 646, 1241
Secondary eclipses can
also put limits on the visible
albedo. The MOST
satellite finds
A(HD209458b)<0.25 (1s)
(Jupiter=0.5, 300-700 nm). Why so dark?
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!
Secondary
ecplises in the
IR with Spitzer,
see photons
from the hot
Jupiters!
T = 1060 ± 50 K
A = 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.
T = 1060 ± 50 K
A = 0.31 ± 0.14
Charbonneau, D. et al. 2005, ApJ, 626, 523
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