planet formation in a disk with a dead zone
DESCRIPTION
Planet Formation in a disk with a Dead Zone. Soko Matsumura (Northwestern University) Ralph Pudritz (McMaster University) Edward Thommes (Northwestern University). Planet formation and migration in an evolving disk with a dead zone. - PowerPoint PPT PresentationTRANSCRIPT
Planet Formation in a disk with a Dead ZoneSoko Matsumura (Northwestern University)
Ralph Pudritz (McMaster University)Edward Thommes (Northwestern University)
Planet formation and migration in an evolving disk with a dead zone Pollack et al. (1996), Hubickyj et al. (2005): giant planet
formation at a fixed orbital radius (~ 5.2 AU) with no disk evolution
Alibert et al. (2005) studied giant planet formation with migration and disk evolution, and found that planet migration can speed up the formation. Jupiter can be made within about 106 years. Planet migration has to be at least 10 times slower.
One of the problems of the core accretion scenario: planet migration seems to be too fast.
Planet formation and migration in an evolving disk with a dead zone
If a planet is made outside the dead zone, we may not need to artificially slow down the planet migration.
Time [years]
30
20
10
0
Dis
k ra
dius
[AU
]
0 2x106 4x106 6x106 8x106 107
α = 10-2
α = 10-5
Evolution of Dead Zones
Gammie (1996): Mass accretion through the surface layers can explain the observed mass accretion rate onto the central star.
Dead Zone
αactiveαdead
Evolution of Dead Zones
Averaged viscosity
2/12/16 rt
rdtdM
hchc sdeaddeadactivecrit
s
2
1810~
yearM
dtdM
dtdM
solardeadactive
Evolution of Dead Zones
104 105 106 107
Time [years]
100
10
1
0.1
0.01
Dis
k ra
dius
[AU
]
Time [years]
30
20
10
0
Dis
k ra
dius
[AU
]
0 2x106 4x106 6x106 8x106 107
Evolution of Dead Zones
104 105 106 107
Time [years]
100
10
1
0.1
0.01
Dis
k ra
dius
[AU
]
106
104
102
1
10-2
10-4
Sur
face
mas
s de
nsity
Σ [g
cm
-2]
Disk radius [AU]0.01 0.1 1. 10. 100.
104 yrs
105 yrs
106 yrs107 yrs
Mdisk< MJ
Mdisk~ 0.01 Msolar
Pollack et al. (1996)
Planet Formation (core accretion scenario)
Core accretion + Gas accretion
Planet Formation (core accretion scenario)
Core accretion Rapid core growth upto ~10-3 - 10-2 ME (Ida & Makino 1993) Oligarchic growth (e.g. Kokubo & Ida 1998, Thommes et al. 2003)
Gas accretion Scaled with Kelvin-Helmholtz timescale (e.g. Pollack et al. 1996,
Ikoma et al. 2000, Bryden et al. 2000, Ida & Lin 2004)
yeargcmM
M grain
Earth
plgas
12
5.28
1106~
Planet Formation (core accretion scenario)
Pollack et al. (1996): Jupiter can be made within 8 x 106 years at 5.2 AU.
Use the solid surface mass density:
Σs = 300(r/AU)-2 g cm-2
and a planetesimal size (10km).
Oligarchic growth is slower than runaway growth.
100
10
1
0.1
0.01
0.001
Mas
s [M
E]
Time [years]0 2x106 4x106 6x106 8x106 107
Core
Envelope
Total
Planet Formation (core accretion scenario)
Lower opacity speeds up gas accretion (e.g. Ikoma et al. 2000, Hubickyj et al. 2005).
Hubickyj et al. (2005): Jupiter can be made within a few 106 years.
Use a fixed opacity of 0.03 cm2 g-1.
100
10
1
0.1
0.01
0.001
Mas
s [M
E]
Time [years]0 2x106 4x106 6x106 8x106 107
Core
Envelope
Total
Planet Formation in a disk with a dead zone
Initial disk mass is Md ~ 0.01 Msolar and disk temperature is calculated as in Chiang et al. (2001).
Dead zone is initially stretched out to ~ 13 AU.
Planetary core with 0.6 ME is placed at 10 AU.
Standard opacity (1 cm2 g-1) assumed. 0 2x106 4x106 6x106 8x108
Time [years]
100
10
1
0.1
0.01
Dis
k ra
dius
[AU
]
Planet Formation in a disk with a dead zone
0 2x106 4x106 6x106 8x108
Time [years]
100
10
1
0.1
0.01
Dis
k ra
dius
[AU
]
0 2x106 4x106 6x106 8x108
Time [years]
100
10
1
0.1
0.01
Dis
k ra
dius
[AU
]
Decreased opacity (0.03 cm2 g-1) Standard opacity (1 cm2 g-1)
Planet Formation in a disk with a dead zone
100
10
1
0.1
0.01
0.001
Mas
s [M
E]
Time [years]0 2x106 4x106 6x106 8x106
Core
Envelope
Total
100
10
1
0.1
0.01
0.001
Mas
s [M
E]
Time [years]0 2x106 4x106 6x106 8x106
Standard opacity (1 cm2 g-1)Decreased opacity (0.03 cm2 g-1)
Planet Formation in a disk with a dead zone
Planetary core with 0.6 ME is placed at 15 AU.
Core accretion is truncated at 10 ME.
Standard opacity is assumed.
0 2x106 4x106 6x106 8x106 107
Time [years]
100
10
1
0.1
0.01
Dis
k ra
dius
[AU
]
Planet Formation in a disk with a dead zone
0 2x106 4x106 6x106 8x106 107
Time [years]
100
10
1
0.1
0.01
Dis
k ra
dius
[AU
]
Time [years]104 105 106 107
100
10
1
0.1
Mas
s [M
E]
1000
Summary Dead zones evolve rapidly.
From 13 AU to 1 AU within ~ 2 x 106 years.
Dead zones help planet formation by slowing down the migration.
Core mass as well as the difference in viscosities between active and dead zones may affect the evolution of a planet.