FROM THE SCATTERED DISK TO THE OORT CLOUD The Extended Scattered Disk Julio A. Fernández Departamento de Astronomía, Facultad de Ciencias, Montevideo, URUGUAY Adrián Brunini, Tabaré Gallardo, Rodney Gomes The observed population Resonances among Scattered Disk Objects (SDOs) Dynamical evolution of SDOs - Some examples High-perihelion Scattered Disk Objects (HPSDOs) - Origin The diffusion to the Oort cloud - The Neptune barrier Conclusions Scattered Disk, Catania Symposium 1
The Observed Population 82 SDOs discovered through June 2006 80 Sedna perihelion distance (AU) 60 40 20 Classical Belt Plutinos Res 2:3 2004XR190 2004PD112 2000YW134 detached SDOs 2000CR105 SDOs Centaurs Res 1:2 0 10 100 1000 semimajor axis (AU) Mass of the Scattered Disk 0.01 0.1 M (Trujillo et al. 2001; Delsanti & Jewitt 2006) Scattered Disk, Catania Symposium 2
Resonances among SDOs 1 2:5 1 1:3 0.8 Resonance s Strength (relative units) 0.5 3:7 4:9 3:8 2:7 1:4 3:10 3:11 2:9 1:5 2:11 1:6 3:19 4:27 2:15 0.6 0.4 0.2 sin(i) of SDOs population 0 50 60 70 80 90 100 110 120 130 140 150 0 mean barycentric a (AU) (Gallardo 2006) About 40% of the SDOs are found in MMR Inclinations higher than classical belt objects (highest i = 46.7 ) Scattered Disk, Catania Symposium 3
How the Scattered Disk formed? Diffusion from the classical belt: (i) Instability region between 40 43 AU due to overlapping of MMR and secular resonances (Duncan et al. 1995; Jones et al. 2006); (ii) Diffusion from the chaotic borders of the 2:3 and 1:2 MMR (Nesvorný & Roig (2001); (iii) Injection of fragments (1-10 km) from collisions (Davis & Farinella 1997; Stern and Colwell 1997) A fossil scattered disk after Neptune s migration (Gomes 2003) Scattered Disk, Catania Symposium 4
Numerical simulations Two models: MODEL 1 The observed population and their clones (399 objects) (Fernández et al. 2004) MODEL 2 The migration model (an initial population of 10 4 planetesimals between 14 and 26 AU, and Jovian planets at distances 5.65, 8.2, 11.5 and 13.8 AU) (Gomes 2003; Gomes et al. 2005) Scattered Disk, Catania Symposium 5
Dynamical evolution and different end states of SDOs planet 8 7 6 5 a (AU) q (AU) i 100 10 35 25 15 5 15 10 5 0 0 250 500 750 1000 1250 1500 time (Myr) SDO 2002 GY 32 that ends up in Jupiter s zone Scattered Disk, Catania Symposium 6
planet a (AU) 8 5 67 1000 100 2:9 270 180 90 q (AU) i 40 30 20 50 40 30 20 0 500 1000 1500 2000 2500 time (Myr) SDO 1999 DG 8 that ends up ejected in a hyperbolic orbit Scattered Disk, Catania Symposium 7
planet 8 7 6 5 w 270 180 90 a (AU) q (AU) 10000 1000 100 50 40 30 50 i 40 30 0 500 1000 1500 2000 2500 3000 3500 time (Myr) SDO 1999 DP 8 that ends up in the Oort cloud q raises for a while by MMR+KR (Duncan & Levison 1997) Scattered Disk, Catania Symposium 8
Dynamical lifetimes of SDOs 9.8 9.4 log [time (yr)] 9.0 8.6 8.2 30 32 34 36 38 perihelion distance (AU) Dynamical half-life t dyn 10 (q 33.5) 4.7 Gyr Average half-life for different q: t dyn 1.8 10 9 yr Scattered Disk, Catania Symposium 9
Typical energy changes per orbital revolution 4 5 log [ε x (AU 1 )] 6 e=0.5 e=0.9 7 30 40 50 60 perihelion distance (AU) Scattered Disk, Catania Symposium 10
The Neptune barrier Two competing process: decrease of q vs. diffusion of a. At first, as q decreases, e increases keeping a more or less constant (Holman & Wisdom 1993). But when the body approaches Neptune, it will be most likely scattered outward About 60% of the bodies scattered outward have perihelia beyond Neptune s orbit (31 < q < 36 AU) at the moment of reaching the Oort cloud (Holman & Wisdom 1993) Scattered Disk, Catania Symposium 11
Histogram-distributions of the perihelion distances of SDOs when they reach the end states indicated in the figures 20 Hyperbolic ejection number 10 0 20 Transfer to Oort cloud number 10 0 5 15 25 35 perihelion distance (AU) Scattered Disk, Catania Symposium 12
Scattering to the Oort cloud No objects with q > 36 AU are found to diffuse to the Oort cloud Current injection rate of SDOs to the Oort cloud: 5 yr 1 Scattered Disk, Catania Symposium 13
The formation of a high-perihelion scattered disk Orbital evolution of a fictitious body temporarily trapped in the 1:24 MMR with Neptune. The Kozai resonance also works to raise the perihelion to 64 AU (Gomes et al. 2005) Scattered Disk, Catania Symposium 14
The case of 2005 XR 190 Anomalous SDO in a low-eccentricity orbit : q = 51.03 AU, a = 57.4 AU, i = 46.7 Scattered Disk, Catania Symposium 15
Conditions: H = 1 e 2 cos i, H = constant Mean a constant The Kozai resonance 60 50 2004 XR190 inclination (degrees) 40 30 20 2005 EO297 2000 CR105 (82075) 2000 YW134 10 2004 PD112 Sedna (48639) 1995 TL8 0 10 20 30 40 50 60 70 80 90 100 perihelion distance (AU) Scattered Disk, Catania Symposium 16
Distribution of perihelion distances and inclinations Model 1 Scattered Disk, Catania Symposium 17
Model 2 Scattered Disk, Catania Symposium 18
Fraction of HPSDO with respect to the total surviving population Model 1 Scattered Disk, Catania Symposium 19
Model 2 Scattered Disk, Catania Symposium 20
Do MM + Kozai resonances explain all the HPSDO? Almost all... but not Sedna and, perhaps, 2000 CR 105 High-Perihelion Scattered Disk Objects Object q (AU) a (AU) i 2000 CR 105 44.3 221 22.7 2000 YW 134 41.2 57.9 19.8 2003 VB 12 (Sedna) 76.1 489 11.9 2004 PD 112 43.6 64.3 6.7 2004 XR 190 51.0 57.4 46.7 2005 EO 297 41.2 63.0 25.0 Alternative explanations: Sun birth in a star cluster Solar companion Rogue planet (Brunini & Melita 2002; Morbidelli and Levison 2004) Scattered Disk, Catania Symposium 21
Sun birth in a star cluster ρ o : central cluster density (M pc 3 ) Big dots : Sedna, 2000 CR 105, 2003 UB 313 (Brasser, Duncan & Levison 2006) Scattered Disk, Catania Symposium 22
Solar companion 800 600 400 200 80 60 40 20 20 40 60 80 200 400 600 800 (Matese, Whitmire & Lissauer 2006; Gomes, Matese & Lissauer 2006) Scattered Disk, Catania Symposium 23
SDOs + HPSDOs + Inner core bodies Scattered Disk, Catania Symposium 24
Conclusions FOSSIL SD vs. LIVE SD (i.e., continuous replenishment from the classical belt. Almost all extended or HPSDOs (q > 40 AU and a > 50 AU) can be explained by the combined action of MMR with Neptune + Kozai resonances. Roughly 12-15% of all SDOs may be HPSDOs. Sedna, and perhaps 2000 CR 105, may require an external perturber (members of the inner core of the Oort cloud). Most of the SDOs diffusing to the Oort cloud have perihelia beyond Neptune s orbit. Neptune acts as a dynamical barrier. On the other hand, no objects diffusing to the Oort cloud have q > 36 AU. Resonance sticking might be the main cause. The contribution of SDOs to the Oort cloud may be quite substantial even at present ( 5 yr 1 ). Scattered Disk, Catania Symposium 25