Download Placing Our Solar System in Context

Formation and Evolution of
Planetary Systems:
The Makings of an
Epicurean Feast
Michael R. Meyer
Steward Observatory, The University of Arizona
Steward/NOAO Joint Colloquium February 12, 2009
Different Flavors of Planet Formation
Are planetary systems like our own are common or
rare among sun-like stars in the Milky Way galaxy?
Q: What are the initial conditions of planet formation?
Q: What is the time available to form gas giant planets?
Q: What is the history of planetesimal collisions vs. radius?
Q: How do the above vary with stellar properties?
Because the answers are subtle,
need large samples over a wide range of ages.
From Active Accretion to Planetary Debris Disks...
Images courtesy of M. McCaughrean, C.R. O`Dell, NASA, and P. Kalas.
For recent review see Meyer et al. (2007) Protostars & Planets V
Planetary debris
disk ~ 100 Myr old
Solar system debris
disk 4.56 Gyr old!
12
Gas-rich disk ~ 1 Myr old
Blackbody Disk with Dynamically Cleared Gap
Star+
Dust
H
H
H
H
Star
Star+
Disk
Color_1
NICMOS/HST Mosaic F810W/F110W/F150W of NGC 2024 (Liu, Meyer, Cotera, and Young 2003, AJ)
Star+
Dust+
Disk
Terrestrial Planets?
Chrondrules?
CAI Formation?
Inner (< 0.1 AU) Accretion Disk Evolution 0.1-10 Myr
Does the observed
range in initial disk
mass (e.g. Andrews &
Williams, 2005) explain
the observed range in
disk lifetimes?
Haisch et al. 2001;
Hillenbrand et al. (2002); Muzerolle et
al. (2003).
Haisch et al. 2001;
Hillenbrand et al. (2002); Muzerolle et
al. (2003).
< t > ~ 3 Myr
Frequency
Terrestrial Planets?
Chrondrules?
CAI Formation?
Inner (< 0.1 AU) Accretion Disk Evolution 0.1-10 Myr
Inner Disk Lifetime
Different Wavelengths Trace Different Radii!
NIR
0.1
MID
FIR
1.0
10.0
sub-mm
100 AU
Star with
magnetospheric
accretion columns
Accretion disk
Disk driven
bipolar outflow
Infalling
envelope
Confounding Variables:
T Tauri Disk Evolution and Errors in Age
Transition Disks:
Espaillat et al. (2007);
Brown et al. (2007)
Few disk parameters correlate:
Bouwman et al. (2008)
Pascucci et al. (2008)
Cortes et al. (2008)
Watson et al. (2007)
How does chemistry affect planet formation?
Gail (2002); Cody & Sasselov (2005); Garaud & Lin (2007); Bond et al. (in prep)
Image courtesy N. Gehrels (PSU)
FUV and (or?) X-rays in action…
Pascucci et al. (2007); Esplainat et al. (2007); Herzeg et al. (2007)
Gas disk chemistry may vary with stellar mass…
Pascucci et al. (in press); cf. Carr & Najita (2008)
Primordial Gas disk lifetimes appear to be < 10 Myr.
No massive gas
disks detected
around 35 stars
with ages 3-100
Myr. Less than
0.1 Mjup remains
to form planets.
Hollenbach et al. 2005; Pascucci et al. 2006/7; Lahuis et al. 2007
Debris Gas? Chen et al. 2007; Roberge et al. 2006; Dent et al. 2005
Rapid Transition time thick to (very) thin inside 1 AU
74 stars 3-30 Myr old:
=> 5 gas-rich disks. =>
no optically-thin
hot dust (< 1 AU).
Silverstone et al. (2006);
Cieza et al. (2007);
and references therein.
Planets as a Function of Stellar Mass:
What Should We Expect?
Planetesimal Formation Timescales:
» tp ~ p x Rp / [ d x d]
– d ~ M*/a and d~ sqrt(M*/a3)
– following Goldreich et al. (2004); Kenyon & Bromley (2006).
– Normalize: @ 3 Myr - [3 Mearth, 5 AU, 1 Msun]
» tp ~ [p x Rp x a5/2]/ [M*3/2].
–
–
–
–
Gives Jupiter mass gas giant planet.
Massive planets farther out surrounding stars of higher mass.
Consistent with observations to date (Johnson et al. 2007).
Yet disks last longer around stars of lower mass!
[Lada et al. (2006); Carpenter et al. (2006).]
0.4
Evolution of Disks Around Sun-like Stars:
Tracing Planet Formation? (Field & Cluster)
LHB
0.0
0.1
0.2
0.3
CAIs Vesta/Mars
Chondrules
Earth-Moon
6.0
7.0
8.0
9.0
Meyer et al. (2008); Kenyon/Bromley (2006); Siegler et al. (2007); Currie et al. ‘07
0.4
Evolution of Disks Around Sun-like Stars:
Tracing Planet Formation? (Field & Cluster)
LHB
0.0
0.1
0.2
0.3
CAIs Vesta/Mars
Chondrules
Earth-Moon
6.0
7.0
8.0
9.0
Meyer et al. (2008); Kenyon/Bromley (2006); Siegler et al. (2007); Currie et al. ‘07
0.4
Evolution of Disks Around Sun-like Stars:
Tracing Planet Formation? (Field & Cluster)
LHB
0.0
0.1
0.2
0.3
CAIs Vesta/Mars
Chondrules
Earth-Moon
6.0
7.0
8.0
9.0
Meyer et al. (2008); Kenyon/Bromley (2006); Siegler et al. (2007); Currie et al. ‘07
Observational Constraints on Planet Formation:
Detecting Hot Protoplanet Collision Afterglows?
Stephenson (1983); Stern (1994); Zahnle et al. (2007)
2M1207B: A Hot Protoplanet Collision Afterglow?
(Chauvin et al. 2004; Schneider et al. 2005; Mohanty et al. 2007)
Mamajek & Meyer (2007)
Miller-Ricci et al.
(submitted)
The connection between planetesimal belts and
presence/absence of giant planets is not clear.
Time
Direct Detection of
Gas Giant Planets
No massive planets
at large radii around
debris disk targets
with large inner gap
Apai et al. (2008)
No link between debris and RV planets found!
Could debris disks be more common than Gas Giants?
Moro-Martin et al. (2007a; 2007b) and Bryden et al. (2006)
See Beichman et al. (2005); Lovis et al. (2006); Alibert et al. (2006) regarding HD 69830.
Spitzer/FEPS
(Meyer et al. 2006)
The Last Word:
Carpenter et al. (2008)
Evolution in Disk Luminosity:
A stars: Su et al. (2006)
G stars: Bryden et al. (2006)
M stars: Gautier et al. (2007)
Distribution of Inner Hole Sizes
A Picture is Worth 1024 x 1024 Points on an SED…
Spitzer @ MIPS-24
JWST-MIRI
Sub-mm Observations of Debris Disks:
Carpenter et al. (2005); Greaves et al. (2006; 2008); Liu et al. (2004)
Evolutionary Diversity: What role might multiplicity play?
Complex Story T Tauri Binaries vs. Separation
Debris Disks not inhibited
Simon & Prato (1995); Jensen et al. (1994)
by companions!
McCabe et al. (2006); White & Ghez (2001)
Trilling et al. (2007)
Patience et al. (2008); Pascucci et al. (2008)
Wyatt et al. (2003)
Are planetary systems like our own are common or
rare among sun-like stars in the Milky Way galaxy?
Primordial Disk Evolution:
- disks around lower mass stars are less massive and live
longer than their more massive counterparts.
- large dispersion in evolutionary times could indicate
dispersion in initial conditions.
- evolution appears to proceed from inside-out as expected.
Are planetary systems like our own are common or
rare among sun-like stars in the Milky Way galaxy?
Change you can believe in!
- transition time from primordial to debris is << 1 Myr.
- planetesimal belts evolve quickly out to 3-30 AU.
- any evidence for warm dust gone by 300 Myr.
- some evidence that warm debris more common in clusters?
Debris Disk Evolution:
- currently detectable systems are collision-dominated.
- more common around stars of higher mass.
- evolutionary paths are diverse.
- consistent with our solar system being common.
- connection to planetary systems unclear.
Are systems without debris those with dynamically full
planetary systems, or those without any planets?
Benefits of Direct Detection:

Enable estimate of internal energy source of planet:
» Assess energy available for life.
» Viability of planet tectonics? [Valencia et al. 2007].

Enable study of atmospheric composition:
» Assess possible surface chemistry.
» Non-equilibrium chemistry [Kaltenegger et al. 2007]?

Unique tool to understand planet formation!
» ‘Merger tree’ determines heating (volume) to cooling (surface area).
Studying Disks and Planets in 2013?
Meyer et al. (2007)
“In the Spirit of Bernard Lyot”
NIRCam Instrument (M. Rieke, PI)
FGS/TFI Instrument (R. Doyon, PI)
MIRI Instrument (Rieke & Wright)
Diffraction Suppression Techniques:
Krist et al. (2007)
Sivaramakrishnan et al. 2008
Direct Detection: Solving The Problem
To find other Earths, the problem is detail, not light gathering.
The Next Big Step: Extremely Large Telescopes