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Formation of the
Solar System
Simulation
Terrestrial & Jovian planets
Discussion
Given the composition of the solar nebula,
why do you think all the terrestrial planets
have smaller masses than the Jovian
planets?
98% hydrogen and helium
1.4% hydrogen compounds – CH4, NH3, H2O
0.4% silicate rocks
0.2% metals
Discussion
Can the Earth hold hydrogen and helium
gas in its atmosphere? How do you know?
Discussion
Do you think any of the other terrestrial
planets hold hydrogen and helium gas?
Discussion
Why do you think the cores of all the Jovian
planets have a mass about 10 times the
mass of the Earth?
Jovian Planets
Once at protoplanet reaches a mass of about
10 times that of the Earth, it can capture large
amounts of gas directly from the solar
nebular, becoming a Jovian planet.
Discussion
Why do you think Uranus and Neptune
didn’t get as big as Jupiter and Saturn?
What about Pluto and the other
TNO’s
Just the proto-cores of would-be Jovian planets
that never got massive enough to hold H and
He.
Doppler method for extra solar
planet detection
Discussion
What planet characteristics (mass and
distance from the star) will be easiest to find
with the Doppler method? Explain your
reasoning.
Extra Solar planets
Many extra-solar planets are Jupiter-like
planets which lie very close to their star.
NASA’s Kepler mission indicates that hot
Jupiter’s are not very common.
Kepler results
Planetary Migration
Most likely these hot Jupiters formed
beyond the frost-line, but due to close
encounters with other protoplanets lost
orbital speed and spiraled in toward the
star.
The Sun
Discussion
Why does the Sun shine?
Discussion
How do you know the Sun is hot?
Discussion
How do we know the temperature of the
Sun?
Discussion
Why is there less solar intensity at sea level
than there is at the top of Earth’s
atmosphere?
Discussion
Where do you think that energy goes?
Discussion
Why isn’t the Sun a perfect blackbody?
Solar Data
Radius:
Mass:
Composition:
Mean density:
Luminosity:
109 Earth radii
333,000 Earth masses
74% hydrogen
25% helium
1.41 g/cm3
3.86  1026 Watts
Discussion
How do we know the mass of the Sun?
The Sun as a big cosmic light
bulb
Suppose every human being on Earth turned on
1000, 100-watt light bulbs. With about 6 billion
people this would only be 6  1014 watts. We
would need 670 billion more Earth’s doing the
same thing to equal the energy output of the Sun.
Cooling Ember theory
Anaxagoras (500 – 428 B.C.E.) believed the Sun
was a very hot, glowing rock about the size of
Greece.
Discussion
If the Sun were cooling down over time, how
could we tell?
Thermal equilibrium
The Sun is not measurably heating up or
cooling down.
No cooling ember
At the rate that the Sun is emitting energy, the
Sun must have been much hotter just a few
hundred years earlier, making life on Earth
impossible.
The Sun must have an energy source; a way of
generating its own heat.
Discussion
Given the composition of the Sun, why is it
unlikely that it could be heated by the
burning of wood or coal?
Kelvin-Helmoltz contraction
As things contract gravitationally, they become
hotter.
Discussion
Why do you think gravitational contraction
leads to a temperature increase?
Discussion
If the Sun is getting its energy from KelvinHelmoltz contraction, how could you prove
this? Do you think this is an easy thing to do?
Explain.
Hydrostatic Equilibrium
The Sun is not measurably expanding or
contracting