Chapter 3: Matter and the Nebular hypothesis

element

substance that cannot be broken down to anything simpler by any chemical means

atom

a particle of matter that has the unique properties of an element

radioactivity

the spontaneous breakdown of unstable atoms of an element with the production of energy + other particles

fission

the breakdown of the nucleus of a relatively heavy atom into at least two lighter particles + energy

fusion

the combination of two lighter atoms to make one heavier atom + energy

supernova

the explosive death of a massive star

atomic number

the number of protons in the nucleus of the atom

what three elements were produced by the Big Bang

hydrogen, helium, lithium

deuterium

isotope of hydrogen ²H

formed helium and lithium

how are heavier elements formed?

supernovae → heat and pressure produces heavy elements

nebular hypothesis

suggests that the solar system formed over brief span of time and as a unit, from the collapse of a nebula

nebula

low density cloud of interstellar gas

outline the process of a nebula collapse

1. collapsed region increased in density

2. atoms bang around, generating heat

3. collapse accelerates, more atoms bang and generate heat

4. particles become so densely packed that heat can no longer escape

5. particles near center move at high speeds (very hot) such that they can provide pressure to prevent further collapse

6. great heat means that fusion can occur, releasing more energy and giving rise to a star

red giant

when the sun (star) runs out of hydrogen fuel and expands into a red giant that will destroy most planets

momentum

a measure of an object’s tendency to move at a constant speed along a straight path

angular momentum

a measure of the amount of spin/orbital motion of an object

conservation of angular momentum

if no outside force acts on a spinning/orbiting object, the angular momentum will not change

why is the solar system flat and the planets move in the same direction?

a net rotation of cloud objects

conservation of angular momentum → as the cloud contracts, it rotates faster and leads it flattening out

dew point temperature

temp to which air must be cooled to reach water saturation, after which water molecules form

composition of nebula

homogenous composition

temperature of nebula

temperature gradient

cooler outer parts → everything condensed into particles and droplets

hotter parts near sun → most remain gasoues

refractory elements

elements that do not readily respond to heat

how did planets form

closer planets like mercury had refractory elements condense, where further planets like Jupiter everything condensed

accretion

objects orbiting gently collided, wound up sticking together leading to increased gravitational force

planetesimals

small pebbles sticking together from accretion accumulate, forming small planets

10-100 km across

protoplanets

planetesimals colliding and forming larger planets

solar wind

a continuous outflow of charged particles that stream through the solar system

removed leftover gases from solar system

what proof is there that leftover gases were swept from the solar system?

• T Tauri stars have very strong winds, enough to drive gas out of solar system

  • atmospheres around planets are not what they were when first formed → must have been swept off

why does earth have two atmospheres

active geology leading to outgassing

bombardment rate

number of collisions of orbiting stones, planetesimals, etc.

decreased as time passed

how have collision affected the planets?

• why uranus is on its side

• why venus rotation is in retrograde

• how the moon orbits the earth

• why mercury’s orbital inclination varies