Transcript Slide 1
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 1 Pluto and Charon Radius Mass Surface composition Atmospheric composition Albedo 2 Pluto’s heliocentric motion “The origin of Pluto’s 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: Pluto’s orbital period is exactly 3/2 that of Neptune.” [Malhotra, 1993] 3 Trans –Neptunian Populations × scattered disk bodies Outer Solar system: ● classical bodies Current Situation resonant bodies Scattered disk hot classical KBOs Kuiper belt Kuiper Belt: Classical KBOs cold classical KBOs resonant population classical belt Plutinos Escaped from Kuiper Belt: ShorP. Comets dynamically cold hot population Centaurus population Scatterd 4 [Morbidelli and Brown, 2003] Long-term stability of orbits in the Kuiper Belt i=1◦ [Duncan, Levison, Budd, 5 1995] Long-term stability of orbits in the Kuiper Belt 0 [Duncan, Levison, Budd, 6 1995] Origin of the resonant populations 3:4 2:3 3:5 1:2 ● 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 7 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 Neptune’s region Explains: •Bimodal inclination distribution of the classical KBOs •Colour distribution 8 Binary systems in the Kuiper Belt Formation of Binaries: 1. Two large bodies penetrate one another’s Hill 1. A dozen binary KBOs are known sphere. The loss of energy needed to stabilize the binary orbit can then occur either through dynamical friction from surrounding small bodies, or through2.the gravitational scattering of a third Bound orbits within several large body. [Goldreich, 2002] 1000km distance (0.1-2” separation) 2. Collision of two planetesimals within the sphere of influence of a third body during low-velocity accretion in the solar nebula. [Weidenschilling, 2002] 3. Components with similar 3. Exchange reaction inwidely which separeted a binary whose brightnesses, and primary componentcomparably is much moresized 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 4. Components one other third body in a wide butorbit eccentric orbit. with [Funato, 2004] eccentricities of order unity CFHT HST 9 What we can learn from Pluto’s size? 10 Accretion in the early outer solar system OBSERVATIONAL RESULTS: CONSTRAINTS: 1 1. ONE BODY WITH RADIUS OF ~1000Km (PLUTO) 0 S 300 ergs g M 10M 0 E M 0.1 M c E 3 >50Km BETWEEN 30-50AU 2. ~105 KBOs WITH RADII e 10 0 20 40Myr 3. TIMESCALES COMPARABLE TO THE FORMATION MORE PLUTOS TIMESCALE FOR NEPTUNE <108 yr 2003UB313 5 10 KBOs 11 [Kenyon and Luu, 1999] Lessons from Pluto Orbit unusual More of this kind? Yes, KBOs Pluto & KBOs Origin of these objects Multiplity of Pluto 12 TNB Formation mechanisms Pluto’s size 10M E More Plutos needed for formation of Puto 2003UB313 12 13 Mean motion resonance collision protection mechanism 2:3 MMR Neptune corotating frame 14 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 (5.97×1024 kg) orbits the Sun (1.99×1030 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. 15