Lecture 6 - Solar System Formation Flashcards
what type of elements make up most of the atmosphere? where did they come from?
light elements like He make up most of the atmosphere –> involved in Big Bang
do heavier elements come from the big bang?
no, but they are very important now
what are the 4 main features of the solar system that must be explained by a theory of solar system formation?
- Patterns of motion –> all orbit in same direction+ motion
- Terrestrial and jovian planets
- Asteroids and comets and why they have specific places they reside
- Notable exceptions
what are 3 places where asteroids and comets reside?
- asteroid belt
- kuiper belt
- Oort cloud
what are 2 notable exceptions to the patterns of the solar system?
- rotation of Uranus
- Earth’s moon
what does the Nebula Theory state?
states that our solar system formed from gravitational collapse of a giant interstellar gas cloud (SOLAR NEBULA)
what does nebula mean in latin?
Nebula = cloud
what does the close encounter theory state?
what does this theory NOT explain? (2)
what type of event would this theory require?
states that planets formed from debris torn off the Sun by a close encounter with another star
doesn’t explain orbital motions or 2 types of planets
would require a highly probable event –> very small chance of a star colliding with the sun and cannot account for other types of planetary systems
is the nebular or close encounter theory more probable?
nebular
what is galactic recycling?
the Big Bang only produced H and He and heavier elements were produced from the death of massive stars and mixed with interstellar gas to form new stars
i.e. stars produce heavier elements from lighter ones
describe the series of events in the nebular theory
- solar nebula started as large, spherical cloud of cold, low-density gas
- cataclysmic event triggered the collapse of the cloud
- strength of gravity increased as the cloud got smaller which made the diameter cloud get even smaller and smaller
- cloud became a disk
what could have been the cataclysmic event triggering the collapse of the solar nebula?
impact of a shock wave from the explosion of a nearby star (SUPERNOVA)
what type of physics allows the collapse of the cloud? explain this
ANGULAR MOMENTUM
as the cloud got smaller, it rotated faster (like spinning figure skater) and pulled in more gas and matter as it sped up
- the rapid rotation prevented total collapse into the center so there was INCREASING ANGULAR MOMENTUM and spread out into a DISK
explain why the cloud collapses into a disk
cloud starts off with different clumps of gas moving in random directions at random speeds
the clumps collide and merge as the cloud collapses and each new clump gets the average velocity of the clumps that formed it so the motion becomes MORE ORDERLY and speeds up a lot to cause increased angular momentum that can spread out into a disk
^the collisions reduce up and down motions
what happens when dark matter collapses? why?
forms a sphere because there are no interactions, so there are many up and down motions
what can we see in the solar system that may confirm the nebular theory? how?
we see nebular disks forming elsewhere
there is a spiral pattern indication the presence of 1+ Jovian planets forming in the disk and gaps indicate forming planets
why are simulations helpful?
- helps with intuition bc we cant see or calculate everything
- can map theoretical observations using the laws of physics
- can compare and confirm with actual images
describe what happens inside and outside frost line. what is the difference?
INSIDE FROST LINE: too hot for H compounds to form ices so metal and rock condense into solids
OUTSIDE FROST LINE: cold enough for metal and rock ices to form
accumulation and condensation of dust is different on either side of frostline
describe the formation of terrestrial planets
why are they small?
what happens to gas?
- planetesimals of metal and rock built from small particles of metal and rock inside the frost line as they collide
- gravity assembled the planetesimals into terrestrial planets (ACCRETION)
small bc metal and rock only make up a small amount of material in the solar nebular
gases leave and diffuse out
what is accretion?
many smaller objects collide to form a few large ones
why was accretion different for jovian planets compared to terrestrial planets?
Jovian planets have more condensation of ices
therefore:
1. there was more solid material
2. the solid material contained ice in addition to metal and rock
describe the formation of jovian planets with regards to:
1. size
2. effect of gravity
3. moons
4. what happens to gas
- ice allows for larger planetesimals and planets
- gravity draws in surrounding H and He
- spinning disks around the planet forms large moons by condensation and accretion, then captures small moons
- photons and solar wind blow away leftover gases
how has the rotation of the sun changed over time? why?
the sun rotates much slower now
bc of friction btwn solar magnetic field and solar nebular
what have the leftovers from planet formation/accretion formed?
the leftovers from planet formation/accretion formed asteroids and comets
what are asteroids?
rocky, leftover planetesimals of inner solar system
what are comets? why do they have tails?
icy, leftover planetesimals of outer solar system
have elliptical movements so when they get close to the sun, ice is blown off the back and produces a tail
describe the heavy bombardment of asteroids and comets
during the late stages of solar system formation, leftover planetesimals bombarded other object
why are many asteroids and comets gone now?
- were flung into deep space by gravitational encounters
- collided with planets
where could Earth’s water and H compounds have come from?
brought to Earth by icy planetesimals
what does the nebular theory account for? (4)
what are exceptions likely caused by?
accounts for:
1. terrestrial planets
2. Jovian planets
3. comets
4. asteroids
exceptions likely caused by large collisions or close gravitational encounters
where do unusual moons likely come from? how do they form for Jovian planets?
unusual moons are likely captured planetesimals
for Jovian planets: passing planetesimals must have lost energy to friction in the dense gas that surrounded the planets as they formed –> reducing the orbital energy of the planetesimals and allowing them to switch from an unbound orbit to a bound orbit
what is a characteristic of a spherical moon?
what is a characteristic of a non-spherical moon?
SPHERICAL MOON –> lots of frosted water
NON-SPHERICAL MOON –> impacted by comets
why do we believe Earth’s moon was not captured?
too large!! could not have formed simultaneously because would have accreted from planetesimals of the same type and would have same composition and density
moon has lower density and diff composition than Earth
how do we believe we got the moon?
GIANT IMPACT
Earth-like planet crashed into Mars-sized planetesimal and they shattered
- Earth became molten and rapidly rotated to increase its spin
- some debris joined the planetesimal and formed the moon
what could explain odd rotation of certain planets?
due to giant impacts
what are the 3 exceptions to the rules of the nebular theory?
- captured moons
- our moon
- odd rotation
how would the solar system be different if the solar nebular had cooled with a temp half its actual value?
frostline would be closer to the sun so outer terrestrial planets would be Jovian instead
is the number of planets of each type explained by the nebular theory?
no
