Download Solar System Formation 10-24-12

Formation of the
Solar System
Formation of the Solar System
From interstellar cloud to planetary system
Formation of the Solar Nebula
In a large, slowly rotating cloud of cold gas
 Self gravity begins to
collapse the cloud
_________
 As the cloud gets smaller,
it begins to rotate faster,
due to ______________
conservation of
angular momentum
________________.
 Centripetal force prevents
gas from collapsing in the
plane of rotation
 Gas falling from the top
collides with gas falling
from the bottom and
sticks together in the
ecliptic plane
Formation of the Solar Nebula
In the flat ____________
solar nebula
 The densest region of the
disk (the center) becomes
Sun
the _____.
Eventually,
fusion in the Sun occurs.
 Atoms orbiting in the disk
bump together and form
molecules, such as water.
Droplets of these
molecules stick together to
form ______________.
planetesimals
 Over time, the
planetesimals grow as
more molecules ________
condense
out of the nebula
Formation of the Solar Nebula
Planetesimals grow …
 Differential rotation (due
to Kepler’s laws) will
cause particles in similar
orbits to eventually meet
up. One will _______
accrete the
other, forming a bigger
body.
 The bigger the body, the
greater its gravitational
force, and the more
attraction it has for other
bodies. Further accretion
Protoplanets
will occur. ___________
form.
Formation of the Solar Nebula
Material begins to evaporate
 While protoplanets are
forming, the Sun’s
luminosity is growing, first
due to gravitational
contraction, then due to
_____________.
nuclear ignition
 Regions of the nebula
close to the Sun will get
hot; the outer regions will
stay cool. In the hot
regions, light elements will
evaporate
__________;
only heavy
elements will condense out
of the nebula
Radiation Pressure and the Solar Wind
Two other processes are also important for
driving light gases from the inner part of the
solar system.
Radiation pressure Photons
_______________:
act like particles and push
whatever particles and dust
they run into.
Solar wind The Sun constantly
_________:
ejects (a little) hydrogen and
helium into space. This solar
wind pushes whatever gas and
dust it runs into.
The Pre-Main Sequence Sun
As the Sun formed, it
generated a lot of energy via
gravitational
contraction
_____________________.
During this time, it was
brighter than it is today. The
radiation pressure in the inner
solar system was greater.
In addition, due to
conservation of angular
momentum, the young Sun
was also spinning faster than it
is today. This caused the
solar wind to be stronger.
Accretion
Once the major bodies of the solar system were formed,
most of the remaining debris was either ejected out of the
solar system or accreted onto other bodies by gravitational
encounters.
Differentiation
Early in the history of the solar system, planets would be
molten due to
Continuous accretion of left over
material from the solar system
formation.
Energy from the fission of
radioactive isotopes.
Observations of Protostellar Disks
The solar nebula theory states that young stars
should be surrounded by a disk consisting of
molecular gas and dust. These are now being
observed.
The Age of the Solar System
We can estimate the age of the Solar System by looking
radioactive isotopes These are unstable forms of
at _________________.
elements that produce energy by splitting apart.
The radioactivity of an isotope is characterized by its half____
___ – the time it takes for half of the ______
life
parent to decay into
daughter element. By measuring the ratio of the
its ________
parent to daughter, one can estimate how long the
material has been around.
Radioactive Elements
Isotope
#
#
protons neutron
s
Daughter
Half-life (years)
Rubidium-87
37
50
Strontium-87
47,000,000,00
0
Uranium-238
92
146
Lead-206
4,510,000,000
Uranium-235
92
143
Lead-207
710,000,000
Potassium-40
19
21
Argon-40
1,280,000,000
730,000
5,730
Aluminum-26
13
13
Magnesium26
Carbon-14
6
8
Nitrogen-14
Each of these isotopes spontaneously decays into its daughter. In
each case, the daughter weighs less than the parent – energy is
produced.
Age of the Solar System
When rocks are molten, heavier elements (such as
uranium) will separate out from other elements. (In liquids,
dense things sink, light things rise.) Once the rocks
solidify, radioactive decay will then take over.
3 billion
• On earth, the oldest rocks have ages of __
years
• The oldest asteroids have ages of ____
4.5 billion years
• Rocks from the “plains” on the Moon have ages of
about 3 billion years. The oldest Moon rocks have
ages of 4.5 billion years.
The solar system is therefore 4.5 billion years old.
http://www.astro.psu.edu/users/rbc/a1/340,1,Slide 1