Download Formation of our solar system

The Solar System
• Observations
– Ordered motions of objects
– Two types of planets – Terrestrial (Solid) vs. Jovian
(Gas)
• For example, Mars vs. Jupiter
– Asteroids and comets
– Meteoroids, Meteors, Meteorites
– Exceptions to ordered motions
• Tilt of Earth’s axis, Earth’s Moon, Pluto
• Is there a theory that can explain what we see?
Yes!!
The Solar System:
Sun, Terrestrial, and Jovian planets
Terrestrial (inner) planets
Juvian (outer) planets
•Small
•contains the heavier elements (Fe, Si, O)
•rocky shell over a metallic core
•Accretion began 4.567 billion years ago
•It took about 0.1 billion years
(100 million years) for planets to form
•mostly volatile gases (H,He)
•same composition as the sun,
but internal pressure is too low
for nucleo-synthesis to take place
99.8 % of the total mass of the solar system resides in the sun
Solar Nebular Theory
• Solar System formed through
the collapse of a large cloud of
gas under its own gravity
Eagle Nebula
Lagoon Nebula
Nebular Theory
Nebula
Cloud of dust and gas in space
Formation of our solar system:
The nebular hypothesis (Kant, 1755)
Gravitational Collapse
• Lets look at an animation!
Angular Momentum Conservation also explains why objects
rotate faster as they shrink in radius:
From Cloud to Solar System
• Energy Conservation
– As the nebula contracts, the
energy is concentrated in a
smaller area. This, in turn,
heats the cloud
• Ang. Momentum Cons.
– Causes the cloud to spin
faster
• Cloud Flattens
– The lighter material floats
to the outer edges.
– The more dense material
stays towards the center.
– In our solar system, this
was the formation of our
inner solid and outer
gaseous planets.
How do planets form?
• Through accretion (collecting of material)
– Small particles are able to build larger complexes of
particles through electromagnetic forces
– Eventually the complex becomes large enough to
“attract” pieces through gravitation – planetesimals
– Only the largest planetesimals survive to become
planets
– The smaller pieces collide and merge with the larger
ones or are broken up by gravitational forces
• Question: Why are all of the planets very nearly
spherical in structure?
Formation of our solar system:
The nebular hypothesis (Kant, 1755)
Planetesimals
Formation of our solar system:
The nebular hypothesis (Kant, 1755)
Why are there two types of
planets?
• It boils down to temperature!
•
Gas in the solar nebula was mostly
hydrogen and helium, but there were
trace amounts of hydrogen
compounds, rock, and metals
• Inner parts of disk are “hotter”
than outer parts
• Rocks can be solid at much
higher temperatures than ice
• Inside the “frost line” too hot
for hydrogen compounds to
form
• Outside the “frost line” cold
enough for gases and ices to
condense
Examples
Hydrogen and
Helium Gas
Condensation
Temperature
Hydrogen (H), Do not
Helium (He)
condense in
nebula
< 150 K
Hydrogen
Compounds
Water (H20),
Methane
(CH4),
Ammonia
(NH3)
Rock
Various
Metals
Iron (Fe),
1,000 – 1,600 K
Nickel (Ni),
Aluminum (Al)
500 – 1300 K
Relative Abundance
in Solar System
98%
1.4%
.4%
.2%
Planet Formation
• Terrestrial planets (Mercury, Venus, Earth, and
Mars) all formed 0.3 AU from the sun.
Rock could condense beyond this distance
• Jovian planets (Jupiter, Saturn, Uranus, and
Neptune) all formed beyond the frost line (3.5
AU)
– Hydrogen compounds formed the cores of these planets
• Continues to support nebular theory
• What about planet orbits?
– But more questions remain
Earth formation
Nebula forms out of H, He clouds
and fusion products from now dead stars.
Gravity pulls gas and dust inward, and rotation
makes a accretionary disk. The proto-sun is at
the center and fusion begins when it is hot enough.
Gravity reshapes the
proto-Earth into a sphere
Heavier elements concentrate in the inner rings. Collisions and
gravitational attraction leads to the formation of planetesimals.
Soon after Earth formed, a Mars-size planet collided with
Earth, blasting debris into space that will form our Moon.
Volcanic gases form the atmosphere, and as Earth
cools, moisture condenses and rains into oceans.
Some gases may have come from passing comets.
Does this theory make sense?
• We observe many other stars forming from interstellar
clouds with circumstellar disks
• What has yet to be explained?
1. List the 9 planets in our solar system.
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto (dwarf planet)
2. List each planet and the
main facts about each.
Mercury
• smallest planet
• no atmosphere
• heavily cratered
• smooth terrain (north)
(old volcanic activity)
• deep slopes
• 1 rotation = 59 days
• 1 revolution = 88 days
• Temp: 800 F to -279 F
Venus
• 1 revolution: 225 days
• 1 rotation: 243 days
•Thick clouds
• Volcanic and Tectonic
activity (present)
• 80% plains covered by
volcanic flows
• Temp: 887 F
• Atmosphere is 97% CO2
Earth
• The
Oasis of the Solar System
• 1 rotation: 23 hours, 56 minutes
• 1 revolution: 365.24 days
• Liquid water
• Plenty of nitrogen and oxygen
needed for life
• Earth rotates at 1,532 ft per sec
•Earth revolves at 18 miles per sec
Mars
• The red planet (FeO)
• 1 rotation: 24 hours, 37 min.
•1 revolution: 687 days
• White polar caps
• Large dust storms
• Hurricane force winds
• Large volcanoes and
canyons (Olympus Mons and
Valles Marineris)
• Temp: - 94 F to – 148 F
•Two moons: Phobos and
Deimos (asteroids)
The Asteroid Belt
• Asteroids are small bodies that
are left over from the beginning
of the solar system
• They are rocky objects with
round or irregular shapes up to
several hundred km across,
but most are much smaller.
• May be the remains of an early
planet which broke up.
• The chances of an asteroid
colliding with Earth are very
small! But some do come close
to Earth, like Hermes (closest
approach of 777,000 km).
Jupiter
• largest planet (11 earths in face)
• 1 rotation = 10 hours
• 1 revolution = 12 years
• Great RED Spot
– a cyclonic storm
• hydrogen-helium atmosphere
• winds cause light and dark bands
• immense gravity
• gigantic ocean of liquid hydrogen
• 63 moons (Europa, Io, Callisto,
Ganymede)
Saturn
• 1 revolution: 29.46 years
• 1 rotation: 10 hours, 39
minutes
• Rings (10 m thick) made
of ice and rock particles
• Winds up to 637.5 mph
• Large cyclonic storms
• 60 moons (Titan, Mimas
(death star))
Uranus
• Rotates on its side (98o)
• Complex ring system
• 1 revolution: 84.01 years
• 1 rotation: 17 hours, 54 min
• 27 moons (Miranda, Puck)
The Kuiper Belt
• Region of the Solar System extending beyond the
planets extending from the orbit of Neptune to the outer
edge of the solar system
• Similar to the asteroid belt, but objects are frozen or icy.
• comets: lumps of ice and dust, tails point away from the
sun, have very long orbital periods.
• Examples of Comets: Halley’s (76 years), Hale-Bopp
(Heaven’s Gate Cult), Shoemaker-Levy (plunged into
Jupiter in 1994).
• Interactive Comet Animation
Kuiper Belt
Neptune
• Discovered in 1846,
mathematical prediction
• 1 revolution: 164 days
• 1 rotation: 18 hours
•Winds up to 625 mph
• Great DARK spot – a
large rotating storm
• 13 moons (Triton)
Pluto
• Smaller than our moon!
• 1 revolution: 248 years
• 1 rotation: 6 days, 9 hours
• classified as a dwarf planet
• Average temp: 346 F
• Dirty ice ball
• Part of Kuiper Belt?
• Old Moon of Neptune?
List the terrestrial planets.
Mercury
Venus
Earth
Mars
What does the term, “terrestrial” mean?
Earth-like
List the jovian planets.
Jupiter
Saturn
Uranus
Neptune
What does the term, “jovian” mean?
Jupiter-like
What are the terrestrial planets made of?
Rocky and metallic substances
What are the jovian planets made of?
Hydrogen and Helium Gas
H compunds
(ex. Ammonia, Methane)
Planetesimals
Small, irregular shaped bodies
resulting from colliding bits of
matter.
Asteroids and Comets
Ida
• Asteroids – Rocky leftover planetesimals
• Comets - Icy leftover planetesimals
Hale-Bopp
Asteroid
Small rocky bodies
Comet
Pieces of rocky and metallic materials
Coma
The glowing head on a comet
Meteoroid
A small solid particle traveling
through space.
When is a meteoroid
called a shooting star?
When it enters the earth’s atmosphere.
Meteor
A meteoroid that burns up in
earth’s atmosphere.
Meteorite
A meteoroid that reaches the
earth’s surface.
Other Solar Systems?
• Nearly 600 others
detected
• Can not detect directly
– Even for the largest
planets, light from the
star overwhelms any
light from the planet
• Use indirect evidence
to search for planets
– Gravitational tugs