Download Origin of the Elements and the Earth

QUESTIONS
1. How do we form hypotheses about the formation of our Solar
System?
2. In what ways can we scientifically test ideas about the Solar
System’s formation and early events?
3. What is the Solar System’s destiny?
BUILDING A SOLAR SYSTEM
STEP 1.
FUSE METALS
ORIGIN OF MATTER
•
All matter originated at the Big Bang
•
Primordial nucleosynthesis
•
A few minutes after the big bang, protons were highly dense and very energetic, allowing
fusion
•
For about 17 minutes, nucleosynthesis could occur
BIG BANG NUCLEOSYNTHESIS
•
Discussed by Alpher-Bethe-Gamow in 1940s
H+H D
•
Nearly all deuterium originated in the big bang
•
Also formed 3He, 4He, 7Li
•
~10:1 H:He ratio
•
Beyond that energy required wasn’t amenable
T=1000 s
Lots of fusion
Less fusion
http://webhome.idirect.com/~rsnow/aboutstars.htg/H-RDIAGRAM.gif
STARS AND FUSION
NUCLEAR FUSION
•
The process of forming a new atomic nucleus by the fusing of two or more nuclei
•
Hydrogen is “burned” to form Helium, and further fusion leads to other elements
•
Fusion only occurs at high temperatures (core of the Sun, nuclear bomb, early big bang)
Coulombic Barrier
+
+
H  HE
2H
D
2H
4He
D+H
3He
2 3He
SYNTHESIS OF HEAVIER ELEMENTS
•
Requires bigger, hotter stars
• High temperature means more energy to overcome coulomb barrier
• Also means more frequent collisions between nuclei, so short-lived nuclei can act as
intermediates
MORE BURNING
•
16O
Triple alpha process
8Be
8Be
2 4He
12C
4He
http://www.hacastronomy.com/sn/onion_skin_model.gif
ORIGIN OF HEAVIER ELEMENTS
From Stellar Nucleosynthesis
HEAVIER ELEMENTS
•
Require energy to synthesize
•
No pay for their own nucleosynthesis
•
Supernova
• Form new elements by proton/neutron capture
• Result in the periodic table
http://magic.mppmu.mpg.de/snr.jpg
Anders and Grevasse 1989
Anders and Grevasse 1989
Most abundant elements
easiest to synthesize
Anders and Grevasse 1989
Heavy elements much rarer
than light elements
Anders and Grevasse 1989
Sawtooth pattern from addition
of He nuclei
Anders and Grevasse 1989
Iron peak- the dead end of nucleosynthesis
Anders and Grevasse 1989
Easy to burn light elements so Li, Be, B are depleted
STEP 2.
DESTROY AN OLD STAR
SUPERNOVA 1987A
•
Brightest Explosion since Kepler’s time
•
Guess the year it happened!
•
Ring of expelled gas from earlier
•
Bipolar filaments
SUPERNOVA 1987A
•
Brightest Explosion since Kepler’s time
•
Guess the year it happened!
•
Ring of expelled gas from earlier
•
Bipolar filaments
•
Hubble has been watching…
http://hubblesite.org/newscenter/archive/releases/2004/09/
PLANETARY NEBULA
•
Not actually planetary at all: Herschel
thought they looked like planets, that
they were new planetary systems
forming.
NEBULA
•
Orion Nebula
• ~2000 Solar Masses
STEP 3.
CONDENSE A NEW STAR
YOUNG STARS
•
Material condenses from “small” shock
waves, perturbations in nebula
•
Spinning increases (Moment of Inertia)
•
Fusion begins when P/T is achieved
•
Materials fall into new star and are
ejected
• This modifies the solar system!
STEP 4.
GET A PROPLYD
(PRO)TO(PL)ANETAR(Y D)ISK = PROPLYD
•
Material spins out like record, Earth
•
North and South of Sun, material is
excavated by jets
•
Orion Nebula proplyds 
STEP 5.
BUILD PARTICLES
Anders and Grevasse 1989
Take a gas of this composition
and cool it.
What forms?
FIRST THING TO FORM:
•
Ceramics
•
These are high temperature
minerals
•
First condensates
CALLED CALCIUM-ALUMINUM RICH INCLUSIONS
THEN COME SILICATES AND METAL
•
Olivine and iron
SILICATES MELTED
•
Formed chondrules
VOLATILE MATERIALS
•
Phosphorus
•
Lower temeprature silicates (Na-, K-bearing)
•
Sulfides
•
Ices
Where do they go?
STEP 6.
BUILD MASSES
EARTH FORMED FROM SOLAR SYSTEM DEBRIS
•
Earth and other planets form from a
mixture of rocky material
• Meteorites
• Asteroids
• Comets
Hoba-
www.nmm.ac.uk
ORIGINS OF THE EARTH’S CONSTITUENTS
•
Volatile components, including key biogenic elements, were in short supply on the early
Earth
•
Earth was hot
•
Volatiles were lost or were not delivered
•
Not primordial ( 20Ne, 36Ar)
LOSS OF VOLATILES ON INNER PLANETS
Earth Si and SSAE Normalized Elemental Abundances vs. Condensation Temperature
1.800E+00
Elemental Abundance
1.600E+00
1.400E+00
1.200E+00
P
1.000E+00
H, C, N, O
8.000E-01
6.000E-01
4.000E-01
2.000E-01
0.000E+00
0
500
1000
Condensation Temperature (K)
1500
2000
DELIVERY OF VOLATILES TO THE EARTH
Cometary Delivery
•
Comets, loaded with H 2O and
organics, were the source of volatiles
Late Veneer
•
• Loaded with water
• Outgassing of volatiles led to
hydro + atmosphere
• High flux (possibly) to early Earth
•
D/H ratio is much higher than earth
• What were early comets really
like?
Carbonaceous Chondrites, with
hydrated minerals, were the last
accreted constituent to the early earth
• Consistent with D/H ratio
•
Something odd going on with PGEs
STEP 7.
“CRUSH THE MASSES”
-Stalin
PLANETARY ACCRETION
•
Dust grains and small particles collide and
stick together
•
Accumulate, making larger and larger bodies
•
A miracle occurs
•
Planets form
http://ircamera.as.arizona.edu/NatSci102/NatSci102/images/accretion.jpg
http://blog.stackoverflow.com/wp-content/uploads/then-a-miracle-occurs-cartoon.png
STEP 8.
DIFFERENTIATE THE PLANETS
PROCESSING OF PLANETS
•
Planets accreted and were warmed
• Radioactive decay of short-lived
elements?
• Impact heating
•
Warming causes differentiation of planets
STEP 9.
REARRANGE AND WATCH OUT
CREATING MOONS AND RINGS
•
From Robin Canup:
• Gravity is hell
• Earth-Moon formed from early collision
• Jupiter kept eating its moons
• Saturn’s Rings formed from destroyed ice
moon?
http://www.youtube.com/watch?v=Fwl_JBQtH9o
THE LATE HEAVY BOMBARDMENT
•
Caused by a turbulent outer Solar System
•
4.1 - 3.8 Ga
http://www.youtube.com/watch?v=6LzQfR-T5_A
The Nice Model 
Gomes et al, Nature, 2005
• Giants were at 5-17 AU
• Now at 5-30 AU
http://physics.uoregon.edu/~jimbrau/astr121/notes/chapter15.html
THE LATE HEAVY BOMBARDMENT
•
Caused by a turbulent outer Solar System
•
4.1 - 3.8 Ga
• Ended same time as life “?” showed
up on Earth
•
Effects still seen nightly
ANNOUNCEMENTS…
MEET IN CHE313 NEXT WEEK!
for
METEORITICS
HOMEWORK: DUE SEPT 12 IN CLASS
•
Uploaded to Canvas
•
Read Chapter 8, stopping at 8.8 for
next week!
•
Homework:
1. Chapter 8, problems 1 & 2
2. Chelyabinsk Research Paper
questions
EXTRA CREDIT (2pts, due with HW2, 9/12)
•
We (The Solar System) is now in a
cloud of gas probably blown to us by a
group of super-giants. It is called the
Local Interstellar Cloud(LIC) or the
Local Fluff.
•
Assume:
• T = 7000 K
• 0.1 atoms/cubic cm
•
Using the Ideal Gas Law, Calculate its
pressure. Give units.
http://science1.nasa.gov/science-news/science-at-nasa/2003/06jan_bubble/