Chapter 6 : Formation of Solar System Flashcards
Formation Theory Property 1
Patterns of motion of the large bodies
- orbit in the same direction and plane
Formation Theory Property 2
Existence of two types of planets
- Terrestrial and jovian
Formation Theory Property 3
Existence of smaller bodies
- asteroids and comets
Formation Theory Property 4
Notable exceptions to usual patterns
- rotation of uranus, earth’s moon
nebular theory
states our solar system formed from the gravitational collapse of a giant interstellar gas cloud (solar nebula)
why did the solar nebula heat up as it collapsed?
as the cloud shrank, its gravitational potential energy was converted to thermal energy
what kind of material in the solar nebula could condense at temperatures as high as 1500 K in the inner region of the nebula?
metals
Relevance of nebular theory
-Kant and Laplace proposed nebular hypothesis over two centuries ago
-large amount of evidence now supports this idea
Close Encounter Hypothesis
rival idea proposed that the planets formed from debris torn off the sun by a close encounter with another star
accuracy of close encounter hypothesis
does not explain observed motions and types of planets
Galactic Recycling
Elements that formed planets were made in stars and then recycled through interstellar space
nebular theory evidence from other gas clouds
we can see stars forming in other interstellar gas clouds
what caused the orderly patterns of motion in our solar system?
conservation of angular momentum and flattening
Conservation of Angular Momentum
rotation speed of cloud from which our solar system formed must have increased as the cloud contracted
flattening
collisions between particles in the cloud caused it to flatten into a disk
-spinning cloud flattens as it shrinks
how do collisions between gas particles effect motions?
-gradually reduce random motions
-reduce up and down motions
Why are there two major types of planets?
conservation of energy
as gravity causes cloud to contract…
it heats up
temp of inner parts of disk
hotter than other parts
rock remains solid at…
greater temps then ice
inside the frost line
too hot for hydrogen compounds to form ices
outside the frost line
cold enough for ices to form
how did terrestrial planets form?
- small particles of rock and metal were present inside frost line
- planetesimals of rock and metal built up as these particles collided
how did gravity change the planetesimals?
-assembled planetesimals into terrestrial planets
accretion, process of assembly
-draws planetesimals together to form planets
how did jovian planets form?
-ice could form small particles outside frost line
-larger planetesimals and planets were able to form
how did gravity affect jovian planets?
-gravity of larger planets and rock and ice was able to draw in surrounding H and He gases
Where are the leftover gases?
a combination of photons and solar wind, outflowing matter from sun, blew away the leftover gases
Solar rotation over time
in nebular theory, young sun rotated much faster than now
- friction between solar magnetic field and solar nebular thought to have slowed rotation over time
where did asteroids and comets come from?
Leftovers from accretion process
- heavy bombardment
where are rocky asteroids?
inside frost line
where are icy comets?
outside frost line
origin of earth’s water
water may have come to earth by icy planetesimals
captured moons
unusual moons of some planets may be captured planetesimals
why does our moon exist?
giant impact
odd rotations explanation
giant impact
how would the solar system be different if the solar nebula had cooled with a temperature half its actual value?
jovian planets would have formed closer to the sun
which of these facts is not explained by the nebular theory?
a. 2 main types of planets
b. planets orbit in same direction and plane
c. existence of asteroids and comets
d. number of planets of each type
d. number of planets of each type
considering only the tilt of their axis, which planet would have the most extreme seasons?
uranus
how do we explain “exceptions to the rules”?
bombardment of newly formed planets by planetesimals may explain the exceptions
how do you measure the age of a rock?
-some isotopes decay with a well-known half life
-comparing proportions of those isotopes with decay products tells us the age
how do we know the age of the solar system?
-radiometric dating of meteorites indicates planets formed 4.5 billion years ago
plasma
consists of gas in which many or most of atoms are ionized (missing electrons)
what happens to energy in the sun’s convection zone?
energy is transported outward by the rising of hot plasma
