Formation of Earth

Question 1

The Big Bang

Answer 1

13.7 billion years ago

Explosion so powerful that space itself was propelled outwards almost instantaneously

Question 2

Cosmological Nucleosynthesis:

Answer 2

Most H and He formed shortly (few seconds) after the Big Bang, when T cooled to 1 billion degrees

Question 3

Stellar Nucleosynthesis:

Answer 3

Most heavier elements (metals) formed either in Red Giants or Supernovae by nuclear fusion
…..without these there would be no life!

Question 4

Red Giants

Answer 4

Large stars that have exhausted hydrogen fuel in their cores and go on to ‘burn’ (i.e., fuse) He, C, O, etc.
Creation of elements up through Fe
Extra neutrons can be captured to produce heavier elements

Question 5

Supernovae

Answer 5

Once core is converted to iron, large stars collapse and then explode
Enormous numbers of neutrons produced are captured to produce heavy eleme

Question 6

Terrestrial Planets:

Answer 6

: Mercury, Venus, Earth, Mars

(rocky, dense with density ~4-5 g/cm3)

Question 7

Jovian Planets:

Answer 7

Jupiter, Saturn, Uranus, Neptune

light, gassy, H, He, density 0.7-2

Question 8

How Did We Get our Solar System?

Answer 8

NEBULA: Huge (diameter 1 ly) interstelar cloud of cold, thinly dispersed interstellar gas (hydrogen and Helium) and dust.
Gravitational Collapse: Gravity concentrates most stuff near center. Heat and pressure increase.
Protosun: Central proto-sun rotates faster (probably got initial rotation from the cloud).

. Solar Nebula (100 AU diameter): Rotating, flattening, contracting disk
5. After ~10 million years, material in center of nebula hot enough to fuse H

“…here comes the sun…”

5. Gravitational accretion: planetesimals have sufficient gravity to attract material gravitationally. Large bodies dominate and grow rapidly. The largest bodies form protoplanets. Protomoons form around them. Smaller bodies suffer numerous collisions and fragment. Some planetesimals, through gravitational interactions with the large protoplanets, are ejected into the outer solar system forming the Oort cloud of comets.

Question 9

Early in the Evolution of the Planets

Answer 9

Planetesimals swept up debris
Accretion + Impacts = HEAT
Radioactive decay = HEAT

Eventually the heat begins to melt materials
Iron, silica melt at different temperatures
Iron sinks, volatiles rise – density layering