Nucleosynthetic processes: Fusion: Hydrogen Helium Carbon Oxygen
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Transcript of Nucleosynthetic processes: Fusion: Hydrogen Helium Carbon Oxygen
Nucleosynthetic processes:
Fusion:•Hydrogen•Helium•Carbon•Oxygen
After Fe, neutron addition takes place (rapid and slow processes)
Summary – Solar abundances of the elements:
• H and He are the most abundant elements• Elements with higher atomic numbers decrease in
abundance exponentially• Peak at Fe, unusually low abundances for Li, Be, B• Isotopes with even atomic numbers and mass numbers
more abundant than those with odd atomic numbers• Sun is H-burning to form He, solar system contains
elements formed in older, more massive stars
Meteorites – extraterrestrial rocks that enter the Earth’s atmosphere and strike the Earth’s surface
Basic Classification:• Stony (silicates)
– Chondrites– Achondrites
• Stony-iron (mixed silicate and metal)• Iron (metal)
Falls are witnessed falling through the atmosphere (meteors), finds are found. Most finds are irons.
http://meteorites.asu.edu/
The nebular hypothesis
The solar nebula (gas) contracted, cooled and condensed into dust sized particles that accreted (stuck together as the result of collisions) into protoplanets (asteroid sized bodies) and then larger planets
http://meteorites.asu.edu/
Evidence that chondrites are representative of early solar system materials:
• 1:1 ratio of non-volatile elements to those in the sun• “sedimentary”, non-equilibrated texture - formed by
accretion of condensed particles with little subsequent heating or alteration
• presence of minerals predicted to be formed by condensation of solar nebula, such as corundum, Fe metal, troilite, etc.
Also inferred: achondrites, iron and stony-meteorites represent fragments of accreted planetesimals that had heated internally, melted and differentiated
The nebular hypothesis
The solar nebula (gas) contracted, cooled and condensed into dust sized particles that accreted (stuck together as the result of collisions) into protoplanets (asteroid sized bodies) and then larger planets
Measured quantity =Heat of vaporization
Hypotheses for the formation of Earth (other planets and moons)
• Heterogeneous accretion • Homogeneous accretion• Chondrite mixing
Chondrite minerals:
•Ca-Al inclusions (CAI’s) (corundum, perovskite, melilite, anorthite)•Silicates in chondrules: enstatite, diopside, olivine, anorthite•Metal: Fe, Ni•Troilite (FeS)•Serpentine•Carbonaceous material