10Nov2006 Ge/Ay133

More on Jupiter, Neptune, the Kuiper belt, and the early solar system.

The MMSN – Solid surface density near 1-3 g/cm2 at Jupiter

Simulations suggest that surface densities nearly a factor of ten larger might be needed to form Jupiter in ≤107 yr. The problem is even worse for the `ice giants’ Uranus and Neptune if they formed near their current locations.

Alternatives?

ie

a

What happens to the Kuiper belt if oligarchs migrate/are ejected? (Miso~r3/4, nearly 7 Mearth at 40 AU)

Petit et al. 1999

Gas giants?

Depending on dust opacity, cores may spend a long time in the “plateau” phase before runaway gas accretion. Form cores closely spaced in higher density region.

Radical idea: Investigate what happens dynamically if one of these closely spaced cores reaches the runaway gas accretion stage first.

Step 1: Start with four cores+planetesimal swarm

Nebular surface density ( g/cm2,

Hill radius

For =r-2 and n~5-10rH, get ~equal mass cores (isolation mass), choice of 0 leaves room for planetesimal swarm.

Step 1: Start with four cores+planetesimal swarm (pictorially)

Initial state, no extensive gas accretion yet, so the cores do not strongly stir the swarm or interact.

Neptune crossing

3:2 2:1Plutinos

classical KBOs

scattered KBOs

The question is, can we get from this initial condition to now?

Step 2: Let one core grow, and dominate gravitationally.

Nearby cores can be scattered, eccentricity evolves as

Steady state if

Protoplanet Planetesimals

Thus the planetesimal swarm is key in damping eccentric orbits!

Early on, scattered protoplanet dominates, or

Time scale for eccentricity damping is:

For the default case, the damping time is of order a few to few tens of Myr.

Statistically, how often do we go from here…

… to here?

From whence the Plutinos?

If Neptune’s migration is sufficiently `slow’, KBOs can be trapped into orbital resonances that move outward w/planet. Hard to explain i distribution of `classical’ belt with this much movement!

From whence the Plutinos?

A bit better at later times, but the quantitative results do not match those observed, esp. for the scattered population of KBOs…

“Standard case”:

What if Jupiter forms in “slot #2”?

What happens if you change the number of cores?

What if you allow the planetesimal disk to be more massive?

Classical belt much too massive and extends too far to reproduce observations…

How might you truncate the classical KBO population beyond 40-45 AU? Photoevaporation? Stellar encounter? (Shown here)

Ida et al. 2000

Need to see more distant objects!

35 deg

Ida et al. 2000

What happens if you let a second (“Saturn”) core accrete gas?

This also really helps with the classical KBO issue beyond 40 AU, and keeps Saturn closer to its position in our S.S.

J

S

From whence the Plutinos?

If Neptune’s migration is sufficiently `slow’, KBOs can be trapped into orbital resonances that move outward w/planet.

How smooth is Neptune’s migration? Depends on size distribution:

Numerically, provided most of the mass is in <200 km bodies, OK.

Objects further out? Look for slow movers…

J

S

U

N

P

Orbit refined by “historical” observations:

a=480 AUe=0.85i=12

q=76 AUQ=900 AU

P=10,500 yr

Why is SEDNA’s orbit hard to understand from a solar system (only) point of view?

Numerical integration studies of individual objects from Mike B.:

?

a=480 AUe=0.85i=12

q=76 AUQ=900 AU

P=10,500 yr

Where did it come from?-in situ formation-scattered by modest-sized planet @ ~70AU-close stellar encounter

Where did it come from?-in situ-scattered by modest-sized planet @ ~70AU-close stellar encounter

Where did it come from?-in situ-scattered by modest-sized planet @ ~70AU-close stellar encounter-dense stellar birth environment

Include perturbers well beyond 30-40 AU:

Sampling bias:

To distinguish between the possible models for Sedna’s origin, you need to detect more such objects. The red arc indicates the fraction of Sedna’s orbit in which it can be detected with current technology.

Emerging picture: Dynamic environment, lots of movement!

Radial velocity surveys aresensitive to ~Jupiter/Saturnmass planets out to >5 AU,Neptune masses further in.

http://exoplanets.org/exoplanets_pub.html

Next time: Can we study extrasolar Kuiper belts?