Astronomy 101
The Solar System
Tuesday, Thursday
Tom Burbine
tomburbine@astro.umass.edu
Course
• Course Website:
– http://blogs.umass.edu/astron101-tburbine/
• Textbook:
– Pathways to Astronomy (2nd Edition) by Stephen Schneider
and Thomas Arny.
• You also will need a calculator.
• There is an Astronomy Help Desk that is open
Monday-Thursday evenings from 7-9 pm in Hasbrouck
205.
• There is an open house at the Observatory every
Thursday when it’s clear. Students should check the
observatory website before going since the times may
change as the semester progresses and the telescope
may be down for repairs at times. The website is
http://www.astro.umass.edu/~orchardhill/index.html.
HW #10, #11, #12, #13, and #14
• Due March 30th at 1 pm
What Planet do we know the most
about?
Earth
• The planet we know best
• 70% covered with water
http://college.cengage.com/geology/resources/protected/physicallab/thelab/interior/index.htm
Earth’s crust
•
•
•
•
•
•
•
•
46.6% O
27.7% Si
8.1% Al
5.0% Fe
3.6% Ca
2.8% Na
2.6% K
2.1% Mg
Earth is made of minerals
Mineral
• A naturally occurring, homogeneous inorganic
solid substance having a definite chemical
composition and characteristic crystal structure
• ~4,000 known minerals
– 100 can be called "common"
– 50 are "occasional“
– the rest are "rare" to "extremely rare".
Olivine
• (Mg, Fe)2SiO4
• Fayalite (Fa) - Fe2SiO4
• Forsterite (Fo) - Mg2SiO4
Pyroxenes
•
•
•
•
Examples:
Enstatite - Mg2Si2O6
Ferrosilite - Fe2Si2O6
Augite - (Ca, Na)(Mg, Fe, Al)(Al, Si) 2O6
Augite
Ferrosilite
• Mineral – A naturally occurring, homogeneous
inorganic solid substance having a definite
chemical composition and characteristic crystal
structure
• Rock - naturally occurring aggregate of minerals
Forming Different Mineralogies
• Can be on a planet-scale
• Or a few meters to kilometers
Some minerals form
before other minerals
http://www.gly.fsu.edu/~salters/GLY1000/8Igneous_rocks/Slide16.jpg
What minerals form?
• Depends on the composition of the magma
• Depends how quickly the magma cools
Types of Rocks
• Igneous – rock that solidified from molten or
partially molten material
• Metamorphic - rock that has changed in
composition, mineral content, texture, or structure
by the application of heat or pressure
• Sedimentary – rock formed from material that
was deposited as sediment by water, wind, or ice
and then compressed and cemented
Igneous Rock
http://en.wikipedia.org/wiki/Image:Magma.jpg
Metamorphism
Quartzite
http://en.wikipedia.org/wiki/Image:Quartzite.jpg
Sedimentary
• Examples of two types of sedimentary rock: limey
shale overlaid by limestone
http://en.wikipedia.org/wiki/Image:Limestoneshale7342.jpg
• Rock formed from sediments covers 75-80% of
the Earth's land area
Oldest rocks on Earth
• Oldest dated mineral
– zircon mineral (ZrSiO4) with an age of 4.404 billion
years enclosed in a metamorphosed sandstone
conglomerate in the Jack Hills of the Narryer Gneiss
Terrane of Western Australia.
– Zircons contain trace amounts of uranium and thorium
• Oldest rock on Earth
– The Acasta Gneiss in the Canadian Shield in the
Northwest Territories, Canada has zircons with an age
of 4.031 billion years.
• Other rocks may be older (but are still being
argued about)
Zircon
How do we know what’s
in the interior of the Earth?
How do we know what’s
in the interior of the Earth?
• Seismic Waves – vibrations created by
earthquakes
Seismic Waves
• P waves – primary waves
– (pushing) – travel faster
– can travel through
anything
• S waves – secondary –
(side to side) – travel
slower – only through
solids
• http://alomax.free.fr/alss/examples/hodo/hodo_ex
ample.html
Surface Waves
• Travel on the surface of the Earth
• Love Wave – side by side
• http://www.geo.mtu.edu/UPSeis/images/Love_ani
mation.gif
• Rayleigh Wave – rolling movement
• http://www.geo.mtu.edu/UPSeis/images/Rayleigh
_animation.gif
• Most of the shaking felt from an earthquake is due
to the Rayleigh waves
P (primary) waves
S (secondary) waves
Surface waves: Rayleigh and Love waves
Richter Scale
• Measures the magnitude of an earthquake
• Single number to quantify the amount of seismic energy released
by an earthquake. Amplitude of largest displacement
• Under 6.0 - At most slight damage to well-designed buildings.
Can cause major damage to poorly constructed buildings.
• 6.1-6.9 - Can be destructive in areas up to about 100 kilometers
across where people live.
• 7.0-7.9 - Major earthquake. Can cause serious damage over
larger areas.
• 8 or greater - Great earthquake. Can cause serious damage in
areas several hundred kilometers across.
How do we get information?
• The precise speed and direction of the waves
depends on the composition, density, pressure,
temperature, and phase (solid or liquid)
Which of these bodies have they used
seismic waves to study?
How can you study
the interior of a planet
from space?
Density
• Density = mass/volume
• If the density is higher than the surface rock, there
must be denser material in the interior
Gravity
• If you can measure gravity (force) with a
spacecraft as it rotates around a body, you can
determine how mass is distributed on the body
Magnetic Field
• Tells if a planet has a molten metal interior
• Magnetic field definition:
– a physical field that arises from an electric charge in
motion, producing a force on a moving electric charge
• http://www.youtube.com/watch?v=uj0DFDfQajw
http://www.gcsescience.com/pme1.htm
Earth’s magnetic field is believed to be
caused by the convection of molten iron,
within the outer liquid core along with the
rotation of the planet
Electrons flow
http://geomag.usgs.gov/images/faq/Q6.jpg
http://www.scifun.ed.ac.uk/card/images/left/earth-magfield.jpg
• Magnetic pole moves
http://science.nasa.gov/headlines/y2003/29dec_magneticfield.htm
http://science.nasa.gov/headlines/y2003/29dec_magneticfield.htm
North Magnetic Pole
• However, the "north pole" of a magnet is defined
as the one attracted to the Earth's North Magnetic
Pole
• By this definition, the Earth's North Magnetic
Pole is physically a magnetic south pole
Glatzmeier and Roberts simulations:
Geomagnetic Reversals
• Based upon the study of lava flows of basalt
throughout the world, it has been proposed that
the Earth's magnetic field reverses at intervals,
ranging from tens of thousands to many millions
of years
• The average interval is ~250,000 years.
• The last such event, called the BrunhesMatuyama reversal is theorized to have occurred
some 780,000 years ago.
• The present strong deterioration corresponds to a 10–
15% decline over the last 150 years and has accelerated
in the past several years
• Geomagnetic intensity has declined almost continuously
from a maximum 35% above the modern value, which
was achieved approximately 2000 years ago.
• At this rate, the dipole field will temporarily collapse by
3000–4000 AD
What may happen during the reversal?
• There may be a slight rise in the per capita cancer
rate due to a weaker magnetic field.
• We may also be able to see the northern lights at
lower latitudes
• If you own a compass, it will have difficulty
finding north until the magnetosphere settles.
Van Allen Belts
• The Van Allen radiation belts are rings of
energetic charged particles around Earth, held in
place by Earth's magnetic field
• Outer belt – primarily electrons
• Inner belt – primarily protons
http://www.nytimes.com/2006/08/10/science/space/10vanallen.html
Van Allen Belts
http://en.wikipedia.org/wiki/Image:Van_Allen_radiation_belt.svg
http://csep10.phys.utk.edu/astr161/lect/earth/magnetic.html
James Van Allen
• Sent a Geiger Counter on the first US satellite
Explorer 1
• The Geiger counter began clicking madly as soon
as it reached orbit
Auroras
• Auroras – natural light displays
• Collision of charged particles from Earth's
magnetosphere with atoms and molecules of
Earth's upper atmosphere
• The collisions in the atmosphere electronically
excite atoms and molecules in the upper
atmosphere. The excitation energy can be lost by
light emission or collisions.
• http://www.youtube.com/watch?v=pLi4T4JCALk
Rocks on the Surface
• If you can see rocks on the surface that comes
from the interior, you can study them
• Rocks can deform and flow
• Easier for rock to deform and flow when it is
warmer
Lithosphere
• Lithosphere is a planet’s outer layer of cool and
relatively rigid rock
• Asthenosphere is the region in the upper mantle
characterized by low-density, semi-plastic (or
partially molten) rock material chemically similar
to the overlying lithosphere
Heating of Planet
How does the planetary interior cool off?
• Heat is transported outward
How does the planetary interior cool off?
Plate Tectonics
• Plate tectonics describes the large scale motions of
Earth's lithosphere.
• Venus – does not appear to have plate tectonics
• Mars – maybe
• Satellites of Jupiter – maybe
• Titan (Satellite of Saturn) - maybe
Pangea
• Pangea - One large supercontinent
•
http://upload.wikimedia.org/wikipedia/commons/8/8e/Pangea_animation_03.gif
http://geology.csupomona.edu/drjessey/class/Gsc101/pangea.gif
Principles of Plate Tectonics
1. The surface of the Earth is
composed of lithospheric plates
that are in constant motion.
2. The plates move in response to
plastic flow in the athenosphere.
3. Motion in the asthenosphere is
caused by convection driven by
the Earth’s internal heat.
4. The internal heat comes from
radioactive decay and the latent
heat from the Earth’s formation.
Three Types of Plate Tectonic Boundaries
• Divergent – plates move apart, space is filled with
molten magma
• Convergent – plates collide
• Transform – plates slide horizontally past each other
Divergent plate boundary
When lava cools
• Lava is a mixture of melted
minerals (some are magnetic).
• While lava is liquid, the
minerals will tend to line up
with a magnetic orientation
pointing at the North Pole.
• When the lava solidifies, the
magnetic orientation is frozen
into the rock- essentially; it
will have a “north end” and a
“south end.”
http://www.mrsciguy.com/sciimages/polarity.jpg
Magnetic stripes on Mars
Convergent Plate Boundary
Hot spots
Transform Boundaries
Earth’s Atmosphere
• Layer of gases surrounding the planet Earth that is
retained by Earth's gravity
• The atmosphere
– protects life on Earth by absorbing ultraviolet solar
radiation
– warming the surface through heat retention
(greenhouse effect)
– reduces temperature extremes between day and night.
Air
•
•
•
•
•
(by volume)
78% nitrogen
21% oxygen
1% argon
0.04% carbon dioxide
~1% water vapor
• http://en.wikipedia.org/wiki/File:Atmosphere_lay
ers-en.svg
• http://en.wikipedia.org/wiki/File:Atmospheric_ele
ctromagnetic_opacity.svg
Greenhouse Effect
• The greenhouse effect is the rise in temperature
that a planet experiences because certain gases in
the atmosphere (H2O, CO2, CH4, O3) trap energy
emitted from the surface.
• Visble light hits the surface
• Surface warms and emits infrared radiation
• Atmospheric gases absorb some of the infrared
light
• Surface and atmosphere heat up
Stefan-Boltzman Law
Emitted power (per square meter of surface) = σT4
λ·Tmax = 2,900,00 nm
http://www.ucar.edu/learn/1_3_1.htm
Contribution to Greenhouse Effect
•
•
•
•
water vapor (H2O) 36–72%
carbon dioxide (CO2) 9–26%
methane (CH4) 4-9%
ozone (O3) 3–7%
http://www.ems.psu.edu/~radovic/image0O3.JPG
http://zfacts.com/metaPage/lib/zFacts-CO2-Temp.gif
http://en.wikipedia.org/wiki/File:Global_Carbon_Emission_by_Type_to_Y2004.png
http://scottthong.files.wordpress.com/2007/02/mauna_loa_carbon_dioxide.png
Any Questions?