14. random velocity of planetesimals is pumped up as high as
the escape velocity of protoplanets. This high random veloc- On the ot
in circular o
多様な円盤から生まれる多様な惑星
ity makes the accretion process slow and inefficient and thus
Tgrow longer. This accretion inefficiency is a severe problem HD 192263
with Æ1 e1
for in situ f
Mdisk T cont <Tdisk Tgrow<Tdisk case. It is di
slingshot m
原始惑星系円盤の質量 circular orb
the magneti
may be wea
disks may b
Terrestria
Jovian plan
planetary a
key process
systems.
We confir
holds in
a Æsolid ¼ Æ1 ð
¼ 1=2; 3=
軌道長半径 (中心星からの距離) tions. We d
Fig. 13.—Schematic illustration of the diversity of planetary systems systems dep
against the initial disk mass for 2. The left large circles stand for central
disk profile
円盤の質量の違い → ガス惑星の数と位置の違い time
stars. The double circles (cores with envelopes) are Jovian planets, and the
others are terrestrial and Uranian planets. [See the electronic edition of the growth
18. earing continues through scattering. After orbital time scales and high inclinations. three categories: (i) hot Earth analogs interior to
00 million years the inner disk is composed Two of the four simulations from Fig. 2 the giant planet; (ii) Bnormal[ terrestrial planets
contain a 90.3 M] planet on a low-eccentricity
巨大惑星の移動に伴う惑星系の変化
the collection of planetesimals at 0.06 AU, a between the giant planet and 2.5 AU; and (iii)
M] planet at 0.12 AU, the hot Jupiter at 0.21 orbit in the habitable zone, where the temper- outer planets beyond 2.5 AU, whose accretion
U, and a 3 M] planet at 0.91 AU. Previous ature is adequate for water to exist as liquid on has not completed by the end of the simulation.
sults have shown that these planets are likely a planet_s surface (23). We adopt 0.3 M] as a Properties of simulated planets are segregated
be stable for billion-year time scales (15). lower limit for habitability, including long-term (Table 1): hot Earths have very low eccentric-
Many bodies remain in the outer disk, and ac- climate stabilization via plate tectonics (24). ities and inclinations and high masses because
巨大惑星が落下する際に
周囲の原始惑星の軌道を
大きくかき乱す
they accrete on the migration time scale (105
多様な惑星系形成
niscent of the recently discovered, close-in 7.5 M]
years), so there is a large amount of damping planet around GJ 876 (25), whose formation is
during their formation. These planets are remi- also attributed to migrating resonances (26).
g. 1. Snapshots in time of the evolution of one simulation. Each panel of each body’s inclination on the y-axis scale. The color of each dot
ots the orbital eccentricity versus semimajor axis for each surviving body. corresponds to its water content (as per the color bar), and the dark inner
he size of each body is proportional to its physical size (except for the dot represents the relative size of its iron core. For scale, the Earth’s water
ant planet, shown in black). The vertical ‘‘error bars’’ represent the sine content is roughly 10j3 (28).
