earth Flashcards
how do we know the age pf the universe?
- the red shift = look at an object and record light as a particular freq
- dopler effect = pitch increases as it comes close and decreases as it moves away
how did elements initially form in the universe?
hot elements began to cool and clump together
what is the lightest element?
H+
what does the sun do to H?
it burns to produce He
what do large stars do?
burn He and then C until Fe is formed
how are the rest of the elements made?
during a star’s evolution/ rapidly when a giant star explodes = supernova explosion
what type of nebula is left over from an explosion?
orion
rocky planet formation
coagulation: 10^4, dust grains collide to form cm size particles and these grow to km size
what is runaway accretion?
coagulation: 10^4-10^5
grow by collision to ~1000km planetesimals
growth rate increases with mass so large objects grow faster hence ‘runaway’
oligarchs
10^5-10^6
grow by accreting planets and merging with one another to form ~100 planetary embyros, well spaces and residing in gaps in the planetesimal field
merger of embryo planets
on the time scales 10^7-10^8 embryos collide on this slow time scale, leaving 2-5 earth sized planets
what planet could be a failed embryo?
mars
how do giant planets and ice asteroids form?
- beyond the snow line when water condenses, adding many times by the mass
- cores accrete by similar process to rocky planets
- once a critical mass of 10xearth is reached, accretion of gas can occur to produce gas giants
examples of gas giants
Jupiter and Saturn
why are Uranus and Neptune not gas giants?
may have reached critical mass too late
what do some larger asteroids also contain?
water ice
how was the interior of the earth heated?
by the release of gravitational energy, once grown to 10% of its present size melting began
how did the core form?
dense droplets of Fe descended through the deep magma ocean to form the core
when was core formation complete?
by 50 Ma
what were required to form first before heavy elements could form?
giant stars to form and synthesise through nuclear fusion and explosion
what allowed the differentiation of the inner earth?
the heat of collision and radioactivity which melts rock
