Transcript C12 : The Solar System

C12 : The Solar System
Section 1 : The Solar System
• P. 337 Fig 1
• Sun contains ______% of the mass of the
solar system. → great gravity → holds the
planets and other objects in the solar
system.
• 1 Astronomical unit (Au) – the average
distance between Earth and the Sun.
~ 150 million km.
• Q: Any other body beyond Pluto in the
solar system?
• A: Astronomers are studying the
movements of Pluto to det. whether the
gravity of an object farther out is affecting
Pluto.
Formation of the Solar System and
Planets
• A cloud of gas and dust in space was
disturbed by supernova.
• Explosion caused waves which squeezed
the cloud.
• Squeezing increased the gravity pull and
and the cloud of gas and dust come
together to form solar nebula.
• The cloud began to spin faster as it
collapsed.
• The cloud grew hotter and denser in the
center.
• The edge gets thinner and cooler.
• As the disk got thinner, ptles began to stick
together and form clumps. Some clumps
got bigger forming planets or moons.
• Near the center of the cloud, only rocky
material could stand the great heat.
Example: Earth.
• Icy matter settled in the outer regions of
the disk.
• The center eventually got so hot that it
became a star, the Sun.
• Lighter elements are scarcer in the planets
near the Sun than in planets farther out in
the solar system.
• Planets closer to the Sun travel _______
than planets farther away from the Sun.
Section 2 : The Inner Planets
Mercury
Venus
Earth
Mars
Mercury
Venus
Earth
Mars
Mercury
• Many craters → like
Earth’s Moon
• Cliffs ~ 3 km
• Weak magnetic field
→ iron core
• No atmosphere.
Why?
• Temps: 425°C →
- 170°C
• Closest to Sun
• 2nd smallest planet in solar system
• No moons
Venus
• Earth’s twin : size and
mass very similar.
• Clouds (carbon
dioxide) are very
dense → very little
sunlight enters.
• Heat is absorbed by
CO2 in the atm
→greenhouse effect
• 45°C → 475°C
• Yellow color → clouds of H2SO4
• Surface has craters, volcanoes
• No moons
Earth
• Q: How does Earth’s atm
helps to protect us?
• A: It causes most
meteors to burn up before
they reach the surface. It
also shields us from
Sun’s intense radiation.
• Q: Why does the Earth
appear to be blue?
• A: ocean color
Mars
• Reddish yellow → iron oxide in soil.
• Polar ice caps → made of frozen CO2 & H2O
• Olympus Mons → largest volcano in the solar
system.
• Q: The two closest planets to Earth are
Venus and Mars. But when astronauts
from Earth visit another planet, it will be
Mars rather than Venus. Why?
• A: Venus has very high temps and atm
press (dense clouds) → caused space
probes to malfunction and conditions more
hostile for humans.
• Mar’s atm is much thinner than Earth’s →
mostly CO2.
• Surface temp : - 125°C → 35°C
• 2 small moons – heavily cratered
- Phobos
- Deimos (farther away)
Section 3 : The Outer Planets
Jupiter
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5th planet from Sun
Atm : hydrogen and helium
Largest planet in solar system
Great Red Spot : giant storm about 25 000
km
• At least 61 moons
4 Large Moons of Jupiter
1. Io : active volcanoes
: red and orange → sulfurous compounds
: atm – thin oxygen
: closest to Jupiter
2.
Europa : rocky interior
: 100 km thick crust of ice
: thin O2 atm
: possible ocean as deep as 200
km under the ice
3. Ganymede : crust of ice ~ 500 km thick
: rocky core
: thin oxygen atm
: largest moon (bigger than
Mercury)
4. Callisto : crust of ice and rock a few
hundred km thick
: crust might surround a salty
ocean
: rocky core
: thin CO2 atm
Saturn
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Sixth planet
2nd largest in solar system
Lowest density
Thick atm : hydrogen & helium
Complex ring system
Structure of Saturn
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Saturn’s rings → ice and rock ptles
At least 31 moons
Largest moon : Titan
Atm : Nitrogen; Argon; Methane
Uranus
• 7th planet
• ~ 21 moons
• Largest moon : Titania
: craters & deep valleys
• Gaseous planet
• Atm : hydrogen; helium; methane
• Bluish green → CH4
Neptune
• 8th planet
• Atm : similar to Uranus
• Bluish green → methane
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At least 11 moons
Largest moon : Triton
Atm: nitrogen
Gaseous planet
Pluto
• Smallest planet in solar system
• Orbit round the Sun → 248 years
• Different from other outer planets:
- thin atm
- solid, icy rock surface
• 1 moon : Charon (half the size of pluto)
Section 4: Other objects in the
Solar System
• Comets
• Meteoroids
• Asteroids
Comets
• Halley’s Comet
• Composed of dust & rock ptles (like large
dirty snowball) mixed with frozen water,
CH4 & NH3
Oort Cloud
• Billions of comets surround the solar
system
• Located beyond the orbit of Pluto
• Gravity of the Sun and nearby stars
gravities interact with the comets in the
cloud
• Either escape from the solar system or get
captured into smaller orbits
Structure of Comet
• Approaches Sun → frozen ice, CH4, NH3
vaporize → release dust and bits of rock
• Coma: the gases and released dust form a
bright cloud
• Nucleus: solid part of comet (unmelted
frozen ice)
• Solar wind pushes on the gases and dust
in the coma → form tails
Meteoroids
• When comets
vaporize and break
up → small pieces
from the comet’s
nucleus spread in the
original orbit of the
comet → These
pieces of dust and
rock is called
meteoroids
• Meteoroids which enter Earth are small →
burn up in Earth’s atm → meteor
• Meteor Showers : more meteors enter the
atm of Earth. Occurs when Earth crosses
the orbital path of a comet.
• Meteorite : big meteoroid not burning up in
the atm and hits the Earth. They are debris
from asteroid collisions or broken up
comets.
Asteroids
• Rock similar to the
planet
• Located in asteroid
belt – between orbits
of Mars and Jupiter
• Tiny ptles to rocks
940 km in diameter