Transcript Origin of Our Solar System

Origin of Our Solar System
TEK Objective 5: Earth in space and time. The
student understands the solar nebular
accretionary disk model. The student is
expected to:
analyze how gravitational condensation of solar
nebular gas and dust can lead to the accretion
of planetesimals and protoplanets;
Where did we come from?
Two Main Theories
Sun-like stars usually take around 100 million years to form.
Nebula are star “nurseries”, where stars are born. This
nebular photograph was taken by the Hubble Space
Telescope
A nebula is the product of
a supernova event. The
death of one system, may
well be the birth of
another!
The
Nebular
Hypothesis
In 1755 Immanuel Kant proposed that a
solar nebulae was pulled together by
gravity so that it collapsed into a flat,
rotating disk that eventually coalesced
into the Sun and planets
Solar nebulae
are huge
clouds of dust
and gas
The Nebular Hypothesis
Laplace stated that after
the matter split off, it
coalesced into a planet. The
process repeated itself,
resulting in a planet each
time. The matter left over
was the Sun.
Much like a figure
skater. You may have
noticed that skaters can
spin much faster if they
pull their arms closer to
their bodies. The more
concentrated their body
masses are, the faster
they'll be able to rotate.
Problems With the Nebular
Hypothesis
Used a flat, rotating nebula as the Solar
System's origin to explain why all the
planets orbit in nearly the same plane
and in the same direction
All planets revolve around the Sun in a counterclockwise direction within a 7°
band of the equatorial region of the Sun, and nearly all of them also turn on
their individual axes in a counterclockwise direction as well.
Contradicted the observation that
the Sun contains most of the Solar
System's mass but only a small
fraction of its angular momentum.
Angular momentum is the measure of the tendency of a rotating body to remain
rotating
Problems With the Nebular
Hypothesis
If rings of matter were split off,
as Laplace stated, they
wouldn't be pulled together to
form planets but would
disperse into space.
Process of Nebular Accretion Disk
Formation Hypothesis
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Starts with Solar Nebulae
Disturbance (possibly a Supernova) cause
gradual collapse of Solar Nebulae
Gravity causes cloud to shrink and
compress the center which begins to heat
up
Accretion disk forms as matter spins
around the center and forms a flat disk

Thermal energy evaporates the disk
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Process of Nebular Nebular
Accretion Disk Formation
Hypothesis
Protostar forms with opaque core
Energy is given off by protostar causing a
cooling
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Cooling causes gas to condense into tiny specs of
metal, rock, & ice “Stellar Debris”
Stellar Debris begins
to stick
together
Protoplanet
– small
body to
that
form Planetesimalscould later form a planet
Accrection of Planetesimals forms
Protoplanets Accretion – gradual growth of
planets
by theinto
accumulation
Some Planetsimals
will form
asteroids,of
other smaller bodies
comets, and moons
The Protoplanet Hypothesis
Because of faults
in the nebular
hypothesis, other After many failures,
such as the
explanations of
encounter
theory,
planet formation
astronomers
were sought.
returned to the
nebular hypothesis to
find improvements
during the mid 1900s.
The Protoplanet Hypothesis
Formed
independently
by
Carl von Weizsacker
Gerard Kuiper
The
The solar system begins to
Protoplanet
form as aHypothesis
rotating cloud, or
nebulae, collapses
Instabilities in the nebulae cause
dust particles to stick together
and accrete into billions of
planetesimals with diameters of
about 10 meters. The
planetesimals then collide and
form protoplanets.
Meanwhile, the protosun in the
center of the nebular disk
becomes massive and hot enough
to "turn on" by fusing hydrogen.
The Sun begins to radiate energy
and vaporize dust in the inner part
of the Solar System. The remaining
gas is blown away by solar winds.