Download Part 2: Solar System Formation

Part 2: Solar System Formation
• Our Milky Way Galaxy is
filled with cold, dark clouds
of gas and dust.
• These clouds are mostly
hydrogen and helium with
dust containing mostly iron,
rock, and ice.
• The Solar System is thought
to have formed from a huge,
slowly rotating cloud about
4.5 billion years ago
• A nearby passing star or
stellar explosion may have
caused the cloud to collapse
Collapsing Gas Clouds
• As the cloud collapsed the
original slow spin began to
speed up. This caused the cloud
to flatten into a disk shape.
• The gravitational pull of the
cloud caused it to shrink further
and caused most of the material
to fall towards the core forming
a large bulge.
Collapsing Gas Clouds?
• In the Great Nebula of
the constellation Orion
are huge clouds of gas
and dust.
• Among these clouds
the Hubble Space
Telescope observed
lumps and knots that
appear to be new stars
and planets being
formed.
Planets in Formation?
• Around the star Beta
Pictoris a large disk of
dust and gas has been
observed.
• The light from the star
is much brighter than
the disk so it had to be
blocked for the disk to
appear clearly.
• Disks have been seen
around other stars too
including Vega.
Birth of the Sun
• As material falls into towards
the disk it collides with other
material and heats up and
melts.
• The increasing mass of the
core also increases the
gravitational pull and causes
more material to be pulled in.
• When the mass is large
enough and temperatures
high enough nuclear fusion
reactions begin in the core
and a star is born!
Heating and Condensation of the
Solar Nebula
•
•
•
•
The heat from the Sun prevents
ices from reforming on the dust
grains in the region near the Sun.
Ices condensed only in the outer
parts of the Solar nebula.
In the inner portion of the disk
only materials like iron and
silicates (rock) can condense into
solids. Slowly they form clumps
of material.
In the outer portion of the disk
much more material can
condense as solids including ice.
This extra material allows
clumps to grow larger and faster.
Gravity does the job
• Within the disk, material is
constantly colliding with one
another. If the collisions are not
too violent material may stick
together.
• In the outer parts of the Solar
Nebula the planets become large
enough to have a significant
gravitational pull and collect gas
around them.
• Planets in the inner nebula can not
grow enough to collect much gas.
• Eventually most but not all of the
material was swept up by the
planets.
The Last of the Planetesimals
The remaining material
exists today as
– comets which were flung
out to a region far beyond
Pluto called the Oort
cloud and
– asteroids mostly between
Mars and Jupiter (the
Asteroid Belt) and beyond
Pluto (the Kuiper Belt)