Download Solar System Overview

An Artist’s Impression
The young Sun
solid planetesimals
gas/dust
nebula
Sequence of events
• 1. Nebular disk
formation
• 2. Initial coagulation
(~10km, ~104 yrs)
• 3. Runaway growth (to
Moon size, ~105 yrs)
• 4. Orderly growth (to
Mars size, ~106 yrs),
gas loss (?)
• 5. Late-stage collisions
(~107-8 yrs)
Dust grains
Timescale Summary
Runaway growth
~Moon-size
(planetesimal)
~0.1 Myr
Orderly growth
~Mars-size
(embryo)
~1 Myr
Late-stage accretion
(Giant impacts. Gas loss?)
~Earth-size
(planet)
~10-100 Myr
What does our Solar System consist of?
•
•
•
•
The Sun 99.85% of the mass (78% H, 20% He)
Nine Eight Planets
Satellites (Moons)
Comets, asteroids, Kuiper Belt Objects, etc.
Where is everything?
Note logarithmic scales!
V E
Me
Ma
Terrestrial planets
J
S
U
N P
KB
Gas giants Ice giants
1 AU is the mean Sun-Earth distance = 150 million km
Nearest star (Proxima Centauri) is 4.2 LY=265,000 AU
Me
V E Ma
Inner solar system
1.5 AU
Note
log scales!
Outer solar system
Basic data
Distance
(AU)
Porbital
(yrs)
Protation
(days)
Sun
24.7
Mercury
0.38 0.24 58.6
Venus
0.72 0.62 243.0R
Earth
1.00 1.00 1.00
Mars
1.52 1.88 1.03
Jupiter
5.20 11.86 0.41
Saturn
9.57 29.60 0.44
Uranus
19.19 84.06 0.72R
Neptune
30.07 165.9 0.67
Pluto
39.54 248.6 6.39R
Mass
(1024kg)
2x106
0.33
4.87
5.97
0.64
1899
568
86.6
102.4
0.013
Radius
(km)
r
695950
1.41
5.43
5.24
5.52
3.93
1.33
0.68
1.32
1.64
2.05
2437
6052
6371
3390
71492
60268
24973
24764
1152
See e.g. Lodders and Fegley, Planetary Scientist’s Companion
(g cm-3)
Nebular Composition
• Based on solar photosphere and chondrite compositions,
we can come up with a best-guess at the nebular
composition (here relative to 106 Si atoms):
Element
H
He C
N
O
Ne
Mg Si
Log10 (No. 10.44 9.44 7.00
Atoms)
6.42 7.32 6.52 6.0
Condens.
Temp (K)
120
180
--
78
--
--
6.0
S
Ar
5.65
5.05 5.95
1340 1529 674
40
• Blue are volatile, red are refractory
• Most important refractory elements are Mg, Si, Fe, S
(makes up the rocky planets)
Data from Lodders and Fegley, Planetary Scientist’s Companion, CUP, 1998
This is for all elements with relative abundances > 105 atoms.
Fe
1337
Terrestrial (silicate) planets
Venus
Earth
Mars
Mercury
Moon
Io
Ganymede
• Consist mainly of silicates ((Fe,Mg)SiO4) and iron (plus FeS)
• Mercury is iron-rich, perhaps because it lost its mantle during a
giant impact (more on this later)
• Volatile elements (H2O,CO2 etc.) uncommon in the inner solar
system because of the initially hot nebular conditions
• Some volatiles may have been supplied later by comets
• Satellites like Ganymede have similar structures but have an ice
layer on top (volatiles are more common in the outer nebula)
Useful Data
Venus
Earth
Solar constant (Wm-2)
2620
Obliquity (o)
Titan
Jupiter
Saturn
Uranus
Neptune
1380 594
15.6
50.5
14.9
3.7
1.5
177
23.4
24.0
(27)
3.1
26.7
98
28.3
Orbital period (years)
0.62
1
1.88
(29.4)
11.9
29.4
84
165
Rotation period (hours)
5832
24
24.6
383
9.9
10.7
17.2
16.1
Bond albedo A
0.76
0.4
0.15
0.3
0.34
0.34
0.3
0.29
Molecular wt. m (g/mol) 43
29
43
29
2.2
2.1
2.6
2.6
Tsurface or T1bar (K)
730
288
220
95
165
134
76
72
Surface pressure (bar)
92
1
.007
1.47
n/a
n/a
n/a
n/a
g (ms-2)
8.9
9.8
3.7
1.35
24.2
10.0
8.8
11.1
Teq (K)
229
245
217
83
113
84
60
48
Scale height H (km)
15
8.5
12
23
27
60
28
20
Radius (km)
6052
6370 3390 2575
71,500
60,300 25,000 24,800
Mass (1024 kg)
4.87
5.97
1900
568
Data mostly from Taylor, Appendix A
Mars
0.64
0.13
87
102
F.Nimmo EART164 Spring 11