Section 7. Formation of the Solar System Flashcards
(16 cards)
What is the Nebular hypothesis?
Gravitational collapse of gas in a molecular cloud and conservation of angular momentum formed protoplanetary discs around the young Sun
What is the esitamtion for the minimum mass solar nebula?
Σαr-3/2
What is the lifetime of a protoplanetary disc around a young star?
~107 years
What is the first step of planet formation?
Formation of young Sun and protoplanetary disc by gravitational collapse
What is the second step of planet formation?
Condensation of sub μm dust particles
What is the third step of planet formation?
Growth of particles by pair-wise collisions, up to ~10km planetesimals
What are the problems with forming planetesimals?
Particles can be eroded by higher velocity collisions
Gas drag on particles causes larger particles to spiral in towards the Sun
What are the solutions to the problems for forming planetesimals?
Structures in disc can trap particles in high pressure regions
Streaming instabilities can cause clumps of particles to shield each other from the headwind
What is the fourth step of planet formation?
Growth to protoplanets assisted by mutual gravity
When does protoplanet formation stop?
At the isolation mass when the Hill sphere of the planet has swept out an annulus of the disc
What is the fifth step of planet formation?
More massive cores beyond the snowline, where ices can form
What is the sixth step of planet formation?
Massive cores accrete gas from disc
How are gas giants formed?
Gas fills the Hill sphere of the planet
gas accretion rate increases and becomes a runaway process
When is an ice giant formed instead of a gas giant?
If disc is dispersed during the slow gas accretion phase
What is the seventh step of planet formation?
Terrestrial planets assembled via giant collisions between protoplanets after disc disposal
What is the evidence for giant collisions?
Prescence and composition of Earth’s moon
High density of Mercury
Spin obliquity of Uranus
