EARTHSC 1121 Lecture 4: Lecture 2 Cosmology

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most of Lecture 2 - Cosmology
Where Do Elements Come from?
First generation stars left a legacy of heavier elements
Second generation starts repeated heavy element genesis
Succeeding generations contain more heavy elements
The sun may be a third, fourth or fifth generation star
o The mix of elements found on Earth include:
Primordial gas from the big bang
The disgorged contents of exploded stars
o We really ARE all made out of stardust!
Nebular Theory of the Solar System
The nebular theory of solar system formation
A third, fourth, or ninth generation nebula forms 4.56 Ga (billion years)
o Hydrogen and helium left over from the big bang
o Heavier elements produced via:
Stellar nucleosynthesis
Supernovae
The nebula condenses into a protoplanetary disk
Solar System Formation
The ball at the center grows dense and hot
Fusion reaction begins; the sun is born
Dust in the rings condense into particles
Particles coalesce to from planetesimals (small planets)
Differentiation of Earth (separating things out according to their properties)
Planetesimals clump into a lumpy protoplanet
The interior heats, softens, and forms a sphere
The interior differentiates into:
o A nickel-iron core
o A stony (silicate) mantle
o Low density rock floats to the top and the high density silicate to the bottom
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Overview of the Planets
- Planets make up only .14% of the mass of the solar system the rest is in the sun
- MEMORIZE: the names and order of the planets
o My very educated mother just served us nachos
o Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
How did the solar system form?
- Observations:
o All planets lie in the same plane (ecliptic)
o All planets orbit in the same direction
o Big, gad planets far from the sun
o Smaller, solid planets closer to the sun
o Moons and terrestrial planets show signs of frequent meteorite impacts
Not Earth! We hae the sae aout of ipats ut e a’t fid reord
of them because Earth covers up the impacts
- Measured:
o Average surface temperatures decrease with distance from the sun
o Sun composition
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