Transcript Unit 2 -- Our Solar System

Our Solar System
Chapters 26, 27, and 28
What are Planetary Systems?
• A star with orbiting planets
• Natural by-product of formation of stars
Why do you think they are a natural by-product?
If natural by-product, why don’t astronomers
know of more planets?
• Planets are hard to discover because they give
off no light of their own
How did our Solar System Form?
• Formed from same nebula that created our
sun
• Mostly hydrogen and helium, but had
smaller amounts of carbon, nickel, iron,
aluminum, and silicon.
• Cloud spun around and flattened.
• Clumps began to collide and condense
forming small clumps (planetary seeds)
Nebular Theory
Nebular Theory
1. Solar System formed from rotating cloud
of dust and gas.
2. Sun formed at center
• (4.6 billion years ago)
3. Small debris (planetesimals) collided
eventually gaining enough mass to
become the planets.
4. Heavier materials combined closer to
the sun to form the terrestrial planets.
5. Lighter materials combined further out
to form the gas giants
How do Scientists determine the age of
the Solar System?
• Use evidence from meteorites, moon rocks,
and Earth rocks
• Radiometric Dating shows oldest meteorites
formed more than 4.54 billion years ago (bya).
• Moon rocks also date to 4.5 bya.
• Infer solar system must have formed a bit
earlier (4.6 bya)
Remembering our Sun…
Remembering our Sun…
• What type of reaction produces its energy?
• Nuclear Fusion (Hydrogen atoms combine to
form Helium) (occurs in the core.)
• What holds the sun together during this reaction?
• Gravitational Forces pulling the atoms inward
• What type of star is the sun considered to be?
• Main-Sequence, medium sized star.
• What will be the remaining life cycle of our sun?
• Become Red Giant (burning Helium) then turn
into a white dwarf leaving a nebula cloud of gas
behind
Proximity of Planets and Stars
• Is Earth closer to other planets or other
stars?
•
•
•
•
Planets are much closer than stars.
What evidence do we have to suggest this?
Parallax Angles
Only under gravitational pull of sun, not
other stars.
• Nearest objects have the largest Parallax
angle, while distant objects are too small to
measure.
Our Solar System
•
•
•
•
99.85% of mass contained within the sun
Planets make up most of remaining .15%
What else is in our solar system?
Moons (Planetary Satellites), Dwarf Planets,
Asteroids, and other smaller bodies
• Terrestrial Planets = small and rocky
• Jovian Planets = Huge, gas giants.
• Size is most obvious difference
• Density, chemical make-up, and rate of
rotation are also ways to distinguish
them.
Terrestrial Planets
• Mercury, Venus, Earth, Mars
• Formed in the warmer inner regions of the
disk
• Heat drove off lighter elements, so these
planets were composed of heavier
elements (metals and rock).
• Small planets and couldn’t attract
hydrogen and helium.
Gas Planets
• Jupiter, Saturn, Uranus, Neptune
• Outer regions were rich in icy, lighter
elements.
• They grew large and could capture
hydrogen and helium in their gravitational
force
• Became gas planets rich in hydrogen and
helium with dense, frozen cores.
Atmospheres of Planets
• Depends on mass and temperature of planet
• Planets must be massive enough for gravity to hold
in gases to form an atmosphere.
Jovian (Gas Giants)
•Thick Atmospheres
•Hydrogen, Helium,
Methane, Ammonia
Terrestrial
•Meager atmospheres
Mercury
• Innermost Planet
• Slightly larger than our
Moon
• Very dense
• Large Iron core
• 59 earth days for one
rotation
• Greatest Temperature
Extremes (-173oC to
427oC)
Venus
• Veiled Planet
• Covered in Thick Clouds
• Similar to Earth in size,
density, mass, and
location.
• Volcanism and tectonic
activity shape Venus’s
surface
• Greenhouse Effect
(atmosphere is 97%
CO2)
Earth
• Distance from sun allow
water to exist in all
three phases: solid,
liquid, and gas
• Allows possibility of life.
• Atmosphere 78%
Nitrogen, 21% Oxygen,
mild green house effect
support life.
Mars
•
•
•
•
•
The Red Planet
White Polar Caps
Easy to observe
Thin Atmosphere
Extensive, hurricane-force
dust storms
• Didn’t have enough gravity
to keep its atmosphere
Jupiter
• 2 ½ more massive than all
other planets and moons
combined!
• Most rapid rotation (10
hours)
• Great Red Spot
• Surface likely and “ocean”
of liquid hydrogen
Saturn
• 2nd largest planet
• Ring System composed
of ice and rock
• Active Winds (up to
1500 km/hr)
• Large cyclonic “storms”
Uranus
• The Sideways Planet
• Axis of rotation is
parallel with the
planet’s orbit
• Contains ring system
like all gas giants
• 4x as large, and 15x as
massive as Earth
• Blue, velvety
appearance
Neptune
• The Windy Planet (exceed
1000 km/hr)
• Great Dark Spot
• Very similar to Uranus in
size and mass
Minor Members of our Solar System:
• Asteroids
• Meteoroids
• Comets
Asteroids (Microplanets)
• Small Rocky Bodies
• “Flying Mountains”
• Most orbit between
orbits of Mars and
Jupiter in the Asteroid
Belt
• Occasionally collide and
fragments break off
Meteoroids
•
•
Small solid particle
Meteors enter Earth’s
atmosphere and burn
up (shooting stars)
• Meteorites actually
reach Earth’s surface
Originate from the
following sources:
1. Interplanetary debris.
2. Material from the
asteroid belt.
3. Solid remains of comets.
Comets
• Rocky/Metallic
materials held together
by frozen gases
• Travel in elongated
orbits.
• As approach sun, solar
energy vaporize frozen
gases which produces
glowing head (coma)
• As travel away from
sun, gases refreeze.
Formation of an
Impact Crater
Effects of Meteoroid Impacts…
Effects of Meteoroid Impacts…
• Moon has many craters (largest the size of
Indiana), while Earth only has about a dozen
recognizable impact craters.
Why do we see more traces of Asteroid impacts
on the moon, than we do on Earth?
• Moon has no atmosphere, therefore:
– No weathering or erosion
– No tectonic forces (volcanic eruptions
and plate movements)
When/How was the moon formed?
One hypothesis…
When solar system first formed…
1. Body the size of Mars
impacted Earth
2. Liquefied Earth’s surface
ejecting huge
quantities of crustal
and mantle rock
3. Some debris entered
orbit and later
combined to form the
moon
Lunar Features
• Highlands – Cover farside of the moon
• Highest peak almost has
tall as Mt. Everest
• Maria – dark, smooth
area.
• Ancient beds of lava
• Regolith – layer of gray
debris from meteorite
bombardment (igneous
rocks, glass beads, fine
lunar dust)
Relationships between
Sun, Moon, & Earth:
• Sun provides light, warmth, and energy
• Moon raises tides and illuminates night sky
• Every society in our history has based their
calendar and time keeping system on
motions of the Sun and Moon
Annual Motions
Which Picture Represents our
Spring, Summer, Fall, and Winter?
Relationship between the
Earth, Moon, and Sun
Why are the
Dinosaurs Extinct?
One hypothesis…
• Mass extinction 65 million
years ago
• Due to inability to adapt to
some radical change in
environmental conditions
• Huge meteorite (10 km
diameter) collided with
Earth around Yucatan
Peninsula
• What would have been
effects of huge collision?
• Huge amounts of Dust
and other debris
blasted high into the
atmosphere
• Blocked out sunlight
which stopped
photosynthesis
• Food chains
collapsed
• By the time sunlight
returned, more than ½
of species on Earth had
been whipped out
• How do we know that?
Early Earth:
Very Different than it is today!
• Original atmosphere made up of gases
similar to those released in volcanic eruptions
today (Water vapor, CO2, Nitrogen, and
several trace gases)
• There was no OXYGEN!!
• Oxygen began to accumulate in the
atmosphere about 2.5 billion years ago.
• Believed to be similar to atmospheres of
Venus
Evidence of things from the past…
• Rocks record geological events and changing
life forms of the past
• Earth’s surface and interior have been
changed by the same geological processes
that continue today (uniformitarianism)
• Relative and Radiometric Dating helps to give
scientists an idea of how old things are.
Relative Dating
• Tells us the sequence
in which events
occurred
• Each bed of rock is
older than the one
above it and younger
than the one below it.
• allows us to compare
rock layers in different
geographic areas.
Correlation of
Rock Layers
Radiometric Dating
Fossil
Formation
Two Conditions are important for preservation:
1. Rapid Burial
2. Possession of Hard Parts
Fossils and Correlation
Fossils can also be used
to interpret and describe
ancient environments.
• Any time period can be
recognized by its fossil
content
Index Fossils:
• Widespread
geographically
• Short Life Span of
geological Time
• Occur in Large
Numbers
• Important to
geologists to match
rocks of the same
age.
Geologic Time Scale
• Using their
interpretations of the
rock record, geologists
have divided Earth’s 4.56
billion year history into
units that represent
specific amounts of
time
• It was believed early
Earth had one large
land mass (Pangaea)
which separated into
today’s continents through
plate movements.