the extended scattered disk

8/13/2019 The Extended Scattered Disk

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FROM THE SCATTERED DISK TO

THE OORT CLOUD

The Extended Scattered Disk

Julio A. Fernandez

Departamento de Astronoma, Facultad de Ciencias,Montevideo, URUGUAY

Adrian Brunini, Tabare 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


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The Observed Population

82 SDOs discovered through June 2006

10 100 1000

semimajor axis (AU)

0

20

40

60

80

perihelion

distance

(AU)

SDOs

2004XR190

Sedna

2000YW134

2000CR105

Centaurs

detached SDOsClassical

Belt

Plutinos

Res 1:2

Res 2:3

2004PD112

Mass of the Scattered Disk 0.010.1M(Trujillo et al. 2001; Delsanti & Jewitt2006)



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Resonances among SDOs

0

0.5

1

50 60 70 80 90 100 110 120 130 140 1500

0.2

0.4

0.6

0.8

1

R

esonancesStrength(relativeunits)

sin(i)ofSDOspopulation

mean barycentric a(AU)

4:9

1:3

1:4

1:5

2:5

2:7

2:9

3:8

3:7

3:10

3:11

2:11 1

:6

3:19

4:27

2:15

(Gallardo 2006)

About 40% of the SDOs are found in MMR Inclinations higher than classical belt objects (highest i = 46.7)



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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 (Nesvorny & Roig (2001);(iii) Injection of fragments (1-10 km) from collisions (Davis & Farinella 1997; Stern andColwell 1997)

A fossil scattered disk after Neptunes migration (Gomes2003)



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Numerical simulations

Two models:

MODEL 1The observed population and their clones (399 objects) (Fernandez et

al. 2004)

MODEL 2The migration model (an initial population of104 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)



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5678

planet

100

1000

a

(AU)

90

180

270

2:9

20

30

40

q

(AU)

20

30

4050

0 500 1000 1500 2000 2500

i

time (Myr)

SDO 1999 DG8 that ends up ejected in a hyperbolic orbit



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5678

planet

90

180

270

w

100

1000

10000

a(AU)

30

40

50

q(AU)

30

40

50

0 500 1000 1500 2000 2500 3000 3500

i

time (Myr)

SDO 1999 DP8 that ends up in the Oort cloud

qraises for a while by MMR+KR (Duncan & Levison 1997)



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Dynamical lifetimes of SDOs

30 32 34 36 38

perihelion distance (AU)

8.2

8.6

9.0

9.4

9.8

log

[time(yr)]

Dynamical half-life

tdyn 10(q33.5)

4.7 Gyr

Average half-life for different q: tdyn 1.8 109 yr



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Typical energy changes per orbital revolution

30 40 50 60


7

6

5

4

log[

x

(AU1)]

e=0.9

e=0.5



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The Neptune barrier

Two competing process: decrease ofqvs. diffusion ofa. At first, asqdecreases,e increases keepingamore or less constant (Holman & Wisdom1993).

But when the body approaches Neptune, it will be most likely scattered outward About 60% of the bodies scattered outward have perihelia beyond Neptunes orbit(31< q < 36 AU) at the moment of reaching the Oort cloud

(Holman & Wisdom 1993)



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Histogram-distributions of the perihelion distances of SDOs when

they reach the end states indicated in the figures

5 15 25 35perihelion distance (AU)

0

10

20

number

0

10

20

number

Hyperbolic ejection

Transfer to Oort cloud



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Scattering to the Oort cloud

No objects with q > 36AU are found to diffuse to the Oort cloud Current injection rate of SDOs to the Oort cloud: 5 yr1



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The formation of a high-perihelion scattered disk

Orbital evolution of a fictitious body temporarily trapped in the 1:24 MMRwith Neptune. The Kozai resonance also works to raise the perihelion to 64AU (Gomes et al. 2005)



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The case of 2005 XR190

Anomalous SDO in a low-eccentricity orbit : q = 51.03 AU,a = 57.4 AU, i = 46.7



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The Kozai resonance

Conditions: H =

1 e2 cos i, H= constant

Mean a constant

0

10

20

30

40

50

60

10 20 30 40 50 60 70 80 90 100

inclination(

degrees)


Sedna

2004 XR190

2000 CR105

2004 PD112

(82075) 2000 YW134

2005 EO297

(48639) 1995 TL8



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Distribution of perihelion distances and inclinations

Model 1



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Model 2



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Fraction of HPSDO with respect to the total surviving population

Model 1



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Model 2



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Do MM + Kozai resonances explain all the HPSDO?

Almost all .... but not Sedna and, perhaps, 2000 CR105

High-Perihelion Scattered Disk Objects

Object q(AU) a (AU) i2000 CR105 44.3 221 22.7

2000 YW134 41.2 57.9 19.8

2003 VB12 (Sedna) 76.1 489 11.9

2004 PD112 43.6 64.3 6.7

2004 XR190 51.0 57.4 46.7

2005 EO297 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)



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Sun birth in a star cluster

o: central cluster density (M pc3)Big dots : Sedna, 2000 CR105, 2003 UB313(Brasser, Duncan & Levison 2006)



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Solar companion

20 40 60 8040 200 400 600 800400

20

40

60

80

40

200

400

600

800

400

(Matese, Whitmire & Lissauer 2006; Gomes, Matese & Lissauer 2006)



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SDOs + HPSDOs + Inner core bodies



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Conclusions

FOSSIL SD vs. LIVE SD (i.e., continuous replenishment from theclassical belt.

Almost all extended or HPSDOs (q > 40 AU and a > 50 AU) canbe explained by the combined action of MMR with Neptune + Kozai

resonances.

Roughly 12-15% of all SDOs may be HPSDOs.

Sedna, and perhaps 2000 CR105, 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 beyondNeptunes orbit. Neptune acts as a dynamical barrier.

On the other hand, no objects diffusing to the Oort cloud haveq > 36

AU. Resonance sticking might be the main cause. The contribution of SDOs to the Oort cloud may be quite substantialeven at present ( 5 yr1).


the extended scattered disk

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