Part II: Lessons from Pluto on

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Comets, Kuiper Belt and Solar System Dynamics
Part II Lessons from Pluto on the Origin of the
Solar System

Silvia Protopapa Elias Roussos Lectures on
Origins of Solar Systems February 13-15, 2006
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Pluto and Charon
Radius
Mass
Surface composition
Atmospheric composition
Albedo
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Plutos heliocentric motion
The origin of Plutos unusual orbit-the most
eccentric and inclined of all the planets-remains
a mystery.
The orbits of Pluto and Neptune overlap, but
close approaches of these two planets are
prevented by the existence of a resonance
condition Plutos orbital period is exactly 3/2
that of Neptune.
Malhotra, 1993
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Trans Neptunian Populations
Plutinos
scattered disk bodies ? classical bodies
Outer Solar system Current Situation
resonant bodies
hot classical KBOs
Kuiper belt
Scattered disk
Kuiper Belt
Classical KBOs
resonant population
classical belt
Plutinos
cold classical KBOs
Escaped from Kuiper Belt
ShorP. Comets
dynamically cold population
hot population
Centaurus
Scatterd
Morbidelli and Brown, 2003
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Long-term stability of orbits in the Kuiper Belt
i1?
Duncan, Levison, Budd, 1995
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Long-term stability of orbits in the Kuiper Belt
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Duncan, Levison, Budd, 1995
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Origin of the resonant populations
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? surviving particles removed particles

.
Final distribution of the Kuiper belt bodies
according to the sweeping resonances scenario.
Malhotra,1993

• Explains
• existence of MMRs with Neptune
• large eccentricities of MMRs with Neptune

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Origin of the hot populations
Gomes scenario
Red dots represent the local population,
originally in the 40-50 AU zone Green dots
represent the population coming from Neptunes
region

• Explains
• Bimodal inclination distribution of the
  classical KBOs
• Colour distribution

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Binary systems in the Kuiper Belt
Formation of Binaries
CFHT
1. Two large bodies penetrate one anothers Hill
sphere. The loss of energy needed to stabilize
the binary orbit can then occur either through
dynamical friction from surrounding small bodies,
or through the gravitational scattering of a
third large body. Goldreich, 2002

• A dozen binary KBOs are known
• Bound orbits within several 1000km distance
  (0.1-2 separation)
• Components with similar brightnesses, widely
  separeted and comparably sized
• Components orbit one other with eccentricities of
  order unity

2. Collision of two planetesimals within the
sphere of influence of a third body during
low-velocity accretion in the solar nebula.
Weidenschilling, 2002
HST
3. Exchange reaction in which a binary whose
primary component is much more massive than the
secondary interacts with a third body, whose mass
is comparable to that of the primary. The
low-mass secondary component is ejected and
replaced by the third body in a wide but
eccentric orbit. Funato, 2004
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What we can learn from Plutos size?
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Accretion in the early outer solar system
OBSERVATIONAL CONSTRAINTS
RESULTS

• ONE BODY WITH RADIUS OF 1000Km (PLUTO)
• 105 KBOs WITH RADII gt50Km BETWEEN 30-50AU
• TIMESCALES COMPARABLE TO THE FORMATION TIMESCALE
  FOR NEPTUNE lt108 yr

MORE PLUTOS
KBOs
Kenyon and Luu, 1999
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Lessons from Pluto
Orbit unusual
More of this kind? Yes, KBOs
Pluto KBOs Origin of these objects
Multiplity of Pluto
12 TNB
Formation mechanisms
Plutos size
needed for formation of Puto
More Plutos
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Thank you!
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Mean motion resonance collision protection
mechanism
23 MMR Neptune corotating frame
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Hill sphere
If the mass of the smaller body is m, and it
orbits a heavier body of mass M at a distance a,
the radius r of the Hill sphere of the smaller
body is                 For example,
the Earth (5.971024 kg) orbits the Sun
(1.991030 kg) at a distance of 149.6 Gm. The
Hill sphere for Earth thus extends out to about
1.5 Gm (0.01 AU). The Moon's orbit, at a distance
of 0.370 Gm from Earth, is comfortably within the
gravitational sphere of influence of Earth and is
therefore not at risk of being pulled into an
independent orbit around the Sun.