utsc. astronomy and astrophysics - what’s its purpose in the society? 0. model for freedom of...

UTSC

Astronomy and Astrophysics - what’s its purposein the society?

0. Model for freedom of thinking & cooperation

1. Understanding - solar system functioning and origin - extrasolar planets, and the place of solar system among other systems - sun-Earth connection - chaos

2. Prediction - global warming - impacts

Understanding of extrasolar and solar planetary systems through theory of their formation

Introducing extrasolar systems

Protoplanetary disks

Disk-planet interaction: resonances and torques, numerical calculations, mass buildup, migration of planets

Dusty disks in young planetary systems

Origin of structure in dusty disks

Source: P. Kalas

HD107146

At the age of 1-10 Myr the primordial solar nebulae = protoplanetary disks = T Tau accretion disksundergo a metamorphosis

They lose almost all H and He and after a brief period astransitional disks, become low-gas high-dustiness Beta Pictoris systems (Vega systems).

Beta Pictoris

A silhouette disk in Orionstar-forming nebula

Prototype of Vega/beta-Pic systems

Beta Pictoris

11 micron image analysis converting observed fluxto dust area (Lagage & Pantin 1994)

B Pic b(?) sky?

Chemical basis for universality of exoplanets:

cosmic composition (Z=0.02 = abundance of heavy elem.)

cooling sequence: olivines, pyroxenes dominant, (Mg+Fe+SiO), then H2O

Hubble Space Telescope/ NICMOS infrared camera

HD 141569A is a Herbig emission star>2 x solar mass, >10 x solar luminosity,Emission lines of H are double, because they come from a rotating inner gas disk. CO gas has also been found at r = 90 AU. Observations by Hubble Space Telescope (NICMOS near-IR camera).

Age ~ 5 Myr

transitional disk

HD 14169A disk (HST observations), gap confirmedby the new observations

Gas-dust coupling? Planetary

perturbations? Dust avalanches?

HD 141569A: Spiral structure detected by (Clampin et al. 2003)Advanced Camera for Surveys onboard Hubble Space Telescope

Radiation-pressure instability of opaque disks found at UTSC

r

r

Radial-velocity planetsaround normal stars

-450: Extrasolar systems predicted (Leukippos, Demokritos). Formation in disks-325 Disproved by Aristoteles

1983: First dusty disks in exoplanetary systems discovered by IRAS

1992: First exoplanets found around a millisecond pulsar (Wolszczan & Dale)

1995: Radial Velocity Planets were found around normal, nearby stars,via the Doppler spectroscopy of the host starlight, starting with Mayor & Queloz, continuing wth Marcy & Butler, et al.

Orbital radii + masses of the extrasolar planets (picture from 2003)

These planets were foundvia Doppler spectroscopyof the host’s starlight.

Precision of measurement:~3 m/s

Hot jupitersRadial migration

Marcy and Butler (2003)

~2003

2005

Like us? NOT REALLY

Why?

Diversity of exoplanetary systems likely a result of:

disk-planet interaction a m? (low-medium) e

planet-planet interaction a m? (high) e

star-planet interaction a m e

disk breakup (fragmentation into GGP) a m e? metallicity

X

XXX

X X

Disk-planet interaction:

observation + numerics

A gap-opening body in a disk: Saturn rings, Keeler gap region (width =35 km)This new 7-km satellite of Saturn was announced 11 May 2005.

To Saturn

Masset and Papaloizou (2000); Peale, Lee (2002)

Some pairs of exoplanets may be caught in a 2:1 resonance

Mass flows through the gapopened by a jupiter-class exoplanet

----> Superplanets can form

Binary star on circular orbitaccreting from a circumbinary disk through a gap.

Surface density Log(surface density)

An example of modern Godunov (Riemann solver) code:PPM VH1-PA. Mass flows through a wide and deep gap!

simulation of a Jupiter in a standard solar nebula. PPM(

Ar t

y mow

icz

2 004

)

What permeability of gaps teaches us about our own Jupiter:

- Jupiter was potentially able to grow to 5-10 m_j, if left accreting from a standard solar nebula for ~1 Myr

- the most likely reason why it didn’t: the nebula was already disappearing and not enough mass was available.

Disk-planet interaction:

new strange migrationmode

Migration Type I :embedded in fluid

Migration Type III partially open (gap)

Migration Type II :in the open (gap)

Type I-III Migration of protoplanets/exoplanets Disks repel planets:

Type I (no gap) Type II (in a gap)

Currently THE problem is: how not to lose planetary embryos (cores) ?

II

I

M/M_Earth

TimescaleWard (1997)

Type I-III Migration of protoplanets/exoplanets If disks repel

planets: Type I (no gap) Type II (in a gap)

If disks attract planets: Type III

Q’s: Which way do they

migrate? How fast? Can the protoplanets

survive?

II

I

…....III……..

M/M_Earth

Timescale

Variable-resolutionPPM (Piecewise Parabolic Method)[Artymowicz 1999]

Jupiter-mass planet,fixed orbit a=1, e=0.

White oval = Roche lobe, radius r_L= 0.07

Corotational region outto x_CR = 0.17 from the planet

disk

disk gap (CR region)

Consider a one-sided disk (inner disk only). The rapid inward migration is OPPOSITE to the expectation based on shepherding (Lindblad resonances).

Like in the well-known problem of “sinking satellites” (small satellite galaxies merging with the target disk galaxies),Corotational torques cause rapid inward sinking. (Gas is trasferred from orbits inside the perturber to the outside.To conserve angular momentum, satellite moves in.)

Now consider the opposite case of an inner hole in the disk. Unlike in the shepherding case, the planet rapidly migrates outwards.

Here, the situation is an inward-outward reflection of the sinking satellite problem. Disk gas traveling on hairpin (half-horeseshoe) orbits fills the inner void and moves the planet out rapidly (type III outward migration). Lindblad resonances produce spiral waves and try to move the planet in, but lose with CR torques.

Outward migration type IIIof a Jupiter

Inviscid disk with an inner clearing & peak density of 3 x MMSN

Variable-resolution,adaptive grid (following the planet). Lagrangian PPM.

Horizontal axis showsradius in the range (0.5-5) a

Full range of azimuthson the vertical axis.

Time in units of initialorbital period.

Edges or gradients in disks:

Magneticcavities aroundthe star

Dead zones

Summary of type-III migration New type, sometimes extremely rapid (timescale < 1000

years). CRs >> LRs Direction depends on prior history, not just on disk properties. Supersedes a much slower, standard type-II migration in disks

more massive than planets Very sensitive to disk density gradients. Migration stops on disk features (rings, edges and/or

substantial density gradients.) Such edges seem natural (dead zone boundaries, magnetospheric inner disk cavities, formation-caused radial disk structure)

Offers possibility of survival of giant planets at intermediate distances (0.1 - 1 AU),

...and of terrestrial planets during the passage of a giant planet on its way to the star.

If type I superseded by type III then these conclusions apply to cores as well, not only giant protoplanets.

1. Early dispersal of the primordial nebula ==> no material, no mobility2. Late formation (including Last Mohican scenario)