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½ sheet
and get
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your
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Weekly Schedule Today
•  Hw # 5 due •  Quiz # 4 •  The solar system! •  Lecture Tutorials Thursday •  Li=le more on planets •  The Solar system Lab The auroras, both surrounding the north magneCc pole (aurora borealis) and south magneCc pole (aurora australis) occur when highly charged electrons from the solar wind interact with elements in the earth's atmosphere. Solar winds stream away from the sun at speeds of about 1 million miles per hour. When they reach the earth, some 40 hours aKer leaving the sun, they follow the lines of magneCc force generated by the earth's core and flow through the magnetosphere, a teardrop-­‐shaped area of highly charged electrical and magneCc fields. Green -­‐ oxygen, up to 150 miles in alCtude Red -­‐ oxygen, above 150 miles in alCtude Blue -­‐ nitrogen, up to 60 miles in alCtude Purple/violet -­‐ nitrogen, above 60 miles in alCtude Planets in our solar system Proper.es of the Planets How do we know the proper.es of planets? •  Distance from Sun known by Kepler’s laws.
•  Orbital period can be observed.
•  Radius known from angular size.
•  Masses known from Newton’s laws.
•  Rotation period known from observations.
•  Density can be calculated knowing radius and
mass.
Density = mass/volume Work the following problems. 1)  “Rock A” has a mass of 45 g and a volume of 15 cubic cenCmeters. Calculate its density. 2)  “Rock B” has a volume of 30 cubic cenCmeters and a mass of 60 grams. Calculate its density. Which sample is heavier? •  A ✔ •  B Which sample is more dense? ✔ •  A •  B 3 g/cm3
2 g/cm3 Density = mass/volume 1)  Go to Appendix 3 (page A-­‐4). Choose a planet in Table 3B. Calculate it’s density (in kg/m3) and then compare your results to the actual density. Volume of a sphere = 4/3πr3 (1000 m)3 = (1 km)3 2) Use your density to determine what your planet is made of. Ice = ~1000 kg/m3; Gases < 1000 kg/m3; Rocks ~3000kg/m3 Comparing Terrestrial and Jovian Planets Terrestrial planets:
Mercury, Venus,
Earth, Mars
Jovian planets:
Jupiter, Saturn,
Uranus, Neptune
4.1 An Inventory of the Solar System All orbits but Mercury’s are close to the same
plane.
Differences between the terrestrial planets:
•  Atmospheres and surface conditions are very
dissimilar.
•  Only Earth has oxygen in atmosphere and liquid
water on surface.
•  Earth and Mars rotate at about the same rate; Venus
and Mercury are much slower, and Venus rotates in
the opposite direction.
•  Earth and Mars have moons; Mercury and Venus
don’t.
•  Earth and Mercury have magnetic fields; Venus and
Mars don’t.
Planet densities/differentiation/
http://astro.unl.edu/classaction/solar.html
density over time/planet
characteristics
Components of the solar system • 1 Star
• 8 Planets
• 166 Moons
• Asteroids
• Comets
Components of the solar system • Meteoroids
• Dwarf
Planets
• Kuiper Belt
Objects
Forming the solar system ~4.5 Ga •  FormaCon of accreCon disk –  Collapsing nebula’s gas fla=ens out because of gravity and conservaCon of angular momentum The Concept of Angular Momentum Conservation
of angular
momentum
says that product
of radius and
rotation rate
must be constant.
Therefore, as a dust cloud collapses, its rate of
rotation will increase.
collapse_of_solar_nebula
Forming the solar system •  In the center of the nebula compression begins fusion of hydrogen into helium= SUN •  ElectrostaCc and gravitaConal interacCons cause the dust and ice grains in the disk to accrete into Planetesimals The Forma.on of the Solar System Temperature in cloud
determines where
various materials
condense out; this
determines where
rocky planets and
gas giants form.
Forming the Earth •  AccreCon conCnues unCl the center is hot enough to melt the rock= magma •  Earth forms and begins to differenCate via density Forming the Moon~ 4.53 ± .01 Ga •  Crater the size of Mars •  Melted the Earth and ejected a large part of the mantle into space •  Eventually accreted into the moon Forming the Atmosphere •  Three step process-­‐ –  VolaCle gases during cooling –  Sulfur and CO2 from volcanic erupCons –  Bacteria began to produce oxygen about 2.8 G •  and Oceans Forming the Oceans •  Earth cooled down, clouds formed and it rained Forming the Solar System Synopsis Surface features of Earth, Mars, Venus, and the Moon Interplanetary MaFer Asteroids and meteoroids have rocky
composition; asteroids are bigger.
Meteor- enters
Earth’s
atmosphere
(above)
Asteroid Ida
with its moon,
Dactyl
Meteoritesurvives the
fall lands on
the ground
What Killed the Dinosaurs? The dinosaurs
may have been
killed by the
impact of a
large meteor or
small asteroid.
4.2 Interplanetary MaFer The impact of a large meteor can create a
significant crater.
The Barringer meteor crater in Arizona
4.2 Interplanetary MaFer The Manicouagan
reservoir in
Quebec
Interplanetary MaFer Comets are icy, with some rocky parts.
Unlike other solar system objects they aren’t
confined to the elliptical
Often take millions of years to orbit
Solar Winds
4.2 Interplanetary MaFer The internal structure of the cometary nucleus:
Dirty Snowballs
AnatomyOfAComet
HaleBoppNucleus
http://media.pearsoncmg.com/aw/
Astroid collision/if/if.html?deepImpact
4.2 I
nterplanetary M
aFer The size, shape, and orientation of cometary
orbits depend on their location. Huge supposed
cloud of comets orbiting the sun: Oort cloud
comets rarely enter the inner solar system.
Meteor
showers are M
associated
with comets –
4.2 Interplanetary aFer they are the debris left over when a comet
breaks up.
4.2 Interplanetary MaFer What make’s Earth unique? 1) Plate tectonics 2) Moderate climate (greenhouse effect) 3) Abundant Liquid water Habitable zone and search for life 4.4 Planets Beyond the Solar System Many planets have been
discovered in other solar
systems; this figure
compares two recently
discovered exoplanets
to Neptune and Earth.
http://media.pearsoncmg.com/aw/
aw_chaisson_astronomytoday_6/videos/
ch15/ExtrasolarPlanetsTransit.html
Some
planets
are discovered
4.4 Planets Beyond the Solar Sthrough
ystem the
“wobble” they create in their parent star’s orbit.
http://media.pearsoncmg.com/aw/
aw_0media_astro/if/if.html?
determine_star_velocty_vs_t
4.4 Planets Beyond the Solar System Others are discovered through the periodic
dimming of the parent star’s luminosity.
4.4 Planets Beyond the Solar System These are the orbits of many extra-solar planets
discovered so far. Most have masses closer to
that of Jupiter than that of Earth.
http://astro.unl.edu/classaction/
extrasolarplanets.html