Download Formation of the Solar System - Hadley

Accretion Theory =
Clumping of
gas/dust caused by
gravity forms planets
and stars (our sun)
Nebula
 =A cloud of gas & dust particles
light years across
 1st Generation nebula-formed
right after the big bang & made
of only Hydrogen & Helium gas
 2nd Generation nebula-from
exploded star matter with
heavier elements
Gravity Causes Accretion
 Small masses randomly
collide into bigger
particles
 Increasing particle sizes
have more mass & more
gravity
Skater
video
 Collapsing causes a spin
(angular momentum)
 Spinning results in
flattening (disc shape)
 Sun-formed from
majority of the mass in
the middle
 Remaining mass flattens
into an Accretion disc
 Planetisimals = 100’s of
moon size pieces that
clump to become the
planets
Carina Nebula 7,500ly away. Collapsing
nebula w/ new star formation (see dust
jets) Hubble Telescope
Fusion Begins!
 When central mass has
enough mass, atoms begin to
merge under gravity & fusion
begins
 Fusion explosion blows out
un-clumped dust and gas off
inner planets toward outer
ones
Young star jetting out material in an
accretion disc
news.nationalgeographic.com
Solar System Formation-short
Accretion-long
Spinning out planetisimals
NOVA-Earth Formation 3.5min
Review: Steps of Accretion
1. Nebula condenses under gravity
2. Spins w/ angular momentum
3. Flattening into a disc (frisbee) shape
4. Fusion cleans out inner planets of
unaccreted gasses/dust
5. Gas planets form as they collect
gases ejected from inner planets
6. Planetisimals accrete into planets
Inner Terrestrial Planets
 Closer to the sun
 Rocky (heavier elements)
& small
 Little or no atmospheres
 No to few moons
 (very little gas stuck b/c
hotter, closer to sun)
Outer Gas Giants (Jovian) Planets
 Farther from sun
 Mostly Gas (light elements)
 Thick atmospheres
 Liquid cores w/ ices
 Many moons w/ high ice
content
 (colder so the gas stuck &
became liquid or even
frozen solid)
Volatile gases cooled farther from sun
 Outside 3-4 AU ice grains
condensed (the “snow line”)
to produce gas giants
planets
enough to condense
(solid)
Too
to snow
Interior layers, atmosphere & ocean form
 Heat from collisions &
radioactive material caused
melting
 Dense material sank = core
& Light floated up = crust
 Volcanoes & Comets
produced atmosphere &
oceans
Evidence –Accretion Craters!
 Earth’s craters have
eroded
 Moon-no erosion b/c
no water cycle or
atmosphere
Meteor Crater, Arizona
Meteor Impact
Manicouagan
impact crater in
Quebec, Canada
Evidence-Planet Size & Density Differences
 Inner & outer planet
groups shows some
accretion occurred
before fusion
 Planets may move
after formation (some
Hot Jupiters)
Pluto?
 Teacher “planet” giving an
acceleration boost using
gravity to a “satellite”
student
Evidence- Composition of NonPlanetary Rock
 Asteroids, Meteorites &
Comets unchanged from
nebula-minerals & gases in
ratios expected
 High water & gas content of
comets = ocean &
atmosphere material
Evidence –Flat Spinning Disc
 All Planets orbit CCW (&
most revolve CCW) –
nebula spun as it
condensed giving accreted
material forward
(tangential) momentum
 Spinning caused
centripetal force to flatten
into disc
Asteroid Belt remnants of Planetisimals
 Jupiter pulled planetisimals
out of orbit & pulverized into
small particles.
Evidence-Multiple Massive extinctions
 Accretion of asteroids
caused planet wide
climate change &
extinction events
 K-T extinction 65mya
50% of all species gone
Iridium element found
in asteroids in planet
wide rock layer
Evidence-Age of Solar System Rocks
 Planets & Sun
accreted together so
all same age
 4.6 billion yrs old
(meteorites)
 4.3 byo Earth rocks
(older rocks eroded)
 Age of sun 4.6 byo
Age of Moon
Atmosphere & Oceans evolved after cooling
 1st atmosphere-blown off by


tifhiggins.blogspot.com


alienatmosphere.volcano.jpg
sun’s 1st fusion
2nd Atmosphere –gases from
comet collisions & volcanic gases
Free Oxygen (O2) added 2.5bya
by cyanobacteria (blue-green
algae)-caused mass extinction
Ozone (O3) formed after and
buffered planet from sun
radiation
Ocean water condensed from
comets/volcanoes
Ocean formation
 Other planetary systems
beyond our solar system
First 55 Extra-Solar Planets Discovered
Approximate
masses in terms
of the mass of
Jupiter
Closer
than the
Earth-Sun
distance

Most of the mass of the solar system is contained in the
Sun; the planets

contribute only 0.2 percent.

b. All the planet’s orbits lie roughly in a single plane.

c. The Sun’s rotational equator lies nearly in this plane.

d. The planets and the Sun all orbit in the same west-toeast direction.

e. Planetary orbits are nearly circular

f. Planets differ in composition

g. The composition of the planets varies roughly with
distance from the Sun.

dense, metal-rich planets lie in the inner system.

h. Outer planets are more massive than inner planets, and
most of the mass of

outer planets is composed of hydrogen and helium.