Geoscience Reference
In-Depth Information
These flat disks enshrouding young stars are thought to be a common
feature of stellar evolution and of planetary system formation. Primordial
protoplanetary disks contain gas and dust and supply the raw ingredients
from which the new planetary systems can form. With the help of Doppler
radial velocity measurements and other means, a fruitful of diverse plane-
tary systems come to our sight from the fact of observations, rather than
the mind of theorists. To date, 145 planetary systems (October 18, 2005, see
http://vo.obspm.fr/exoplanetes/encyclo/index.php), containing 169 extra-
solar planets, have been detected about solar-type stars, among which there
are 18 multiple-planet systems, 14 two-planet systems (HD 82943, GJ 876,
HD 168443, 47 UMa, HD 38529, HD 12661, HD 128311 ... ), three-planet
systems (Upsilon And, HD 160691, HD 37124) 2 - 4 and one four-planet sys-
tem 55 Cnc, 5 where the studies of the dynamics or the formation of these
systems are essential to understand how two (or more) planets originate
and evolve there.
In Table 1, some characteristics (the planetary masses, the orbital peri-
ods P , the semi-major axes a and the eccentricities e ) of seven multi-planet
systems are listed. According to the ratios of two orbital periods of the
planets, the planetary systems are usually classified into resonant systems
with P 1 /P 2 < 5:1 (where P 1 , 2 are, respectively, the orbital periods for the
Properties of seven multi-planet systems. a
Table 1.
Planet
M star (M )
M sin i ( M Jup ) i d P (days)
a (AU)
ecc.
GJ 876 b
0.32
1.89
61.02
0.207
0.10
GJ 876 c
0.32
0.56
30.12
0.130
0.27
HD 128311 b
0.84
2.18
458.6
1.099
0.25
HD 128311 c
0.84
3.21
928.3
1.76
0.17
47 UMa b
1.03
2.86
1079.2
2.077
0.05
47 UMa c
1.03
1.09
2845.0
3.968
0.00
HD 82943 b
1.05
1.63
444.6
1.159
0.41
HD 82943 c
1.05
0.88
221.6
0.728
0.54
HD 12661 b
1.07
2.30
263.6
0.823
0.35
HD 12661 c
1.07
1.57
1444.5
2.557
0.20
Ups And b
1.30
0.64
4.617
0.058
0.01
Ups And c
1.30
1.79
241.16
0.805
0.27
Ups And d
1.30
3.53
1276.15
2.543
0.25
55 Cnc b
0.95
0.784
14.67
0.115
0.02
55 Cnc c
0.95
0.217
43.93
0.240
0.44
55 Cnc d
0.95
3.912
4517.4
5.257
0.33
55 Cnc e
0.95
0.045
2.808
0.038
0.17
a The data are adopted from Refs. 2, 4, and 5.
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