Download The Solar System

The Solar System
• What is it like?
• When did it form?
• How did it form
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The planets all orbit the sun in the same direction.
The Sun spins in the same direction.
Most planets spin in the same direction.
counterclockwise
seen from above
the north pole)
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Relative Planetary Radii
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The Distribution of Orbital Radii
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Planet
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
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Orbital Eccentricity Orbital Inclination
0.2056
0.0068
0.0167
0.0934
0.0485
0.0555
0.0463
0.009
0.2488
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7°00'18"
3°23'40"
0°00'00"
1°50'59"
1°18'12"
2°29'20"
0°46'24"
1°46'12"
17°08'30"
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The Inner and Outer Solar Systems
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Pluto
•A “misfit” ?
•Orbit radius like a jovian planet
•Much smaller than any terrestrial planet.
•Comet-like composition (ices, rock)
•Comet-like orbit (eccentric, highly inclined to ecliptic plane).
•Charon is half Pluto’s diameter
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Rocky asteroids
between Mars & Jupiter
Icy comets in vicinity of
Neptune and beyond
Asteroids and comets
far outnumber the
planets and their moons
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Summary: Four Major Features of our Solar System
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When did the Solar System form?
•
•
The solar system is as old as its oldest rocks.
We can find the ages of rocks through analysis of
isotopic ratios.
•
This can be done for rocks on earth and for
meteorites.
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The decay of radioactive elements into
other elements is a key tool in finding
the ages of rocks
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Age dating of meteorites
that are unchanged since
they condensed and
accreted tell us that the
solar system is about 4.6
billion years old.
This coincides with the
age of the Sun.
The Nebular Hypothesis argues that the solar system
formed as a by-product of the formation of the Sun.
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To understand the origin of the solar system we need
to understand the origin and evolution of stars.
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The cloud of gas that gave birth to our solar system resulted from the
recycling of gas through many generations of stars within our galaxy.
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As gravity forced the cloud
to become smaller, it began
to spin faster and faster
[Conservation of angular
momentum.]
And it begins to heat up.
[Conservation of energy.]
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Collisions flatten the cloud into a
disk.
The orderly motions of our solar
system today are a direct result of
the solar system’s birth in a
spinning, flattened cloud of gas.
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We see evidence for spinning
disks of gas and dust around
other stars, especially newly
formed stars
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The nebular
theory
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Fig 9.5
The protostellar cloud is heated by the young star forming at its
center and energy released by the collapsing cloud
Inside the frost line it is too hot for ices to form.
Outside the frost line it is cold enough for ices to form.
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Thermal Structure of the Protoplanetary Nebula
http://dosxx.colorado.edu/~bagenal/1010/SESSIONS/11.Formation.html
The types of planets formed reflect the raw materials available.
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Comets and asteroids are leftover
planetesimals.
• Asteroids are rocky because they
formed inside the ice line.
• Comets are icy because they formed
outside the ice line
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Once formed the proto-planets continue to evolve:
http://dosxx.colorado.edu/~bagenal/1010/SESSIONS/11.Formation.html
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Earth’s moon was
probably created
when a big
planetesimal
slammed into the
newly forming
Earth.
Other large
impacts may be
responsible for
other exceptions
like rotation of
Venus and Uranus
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Over 120 known
extrasolar planets as of
2004
Most are more massive
than Jupiter and closer to
their star than Earth is to
Sun
Revisions to the nebular
theory are necessary!
Planets can apparently
migrate inward
from their birthplaces.
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