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12 Dec 2010
Lecture 17
Largest Asteroids Ceres with diameter 950km
Asteroids are made of Metal and Rock
They are rocky leftovers of planet formation
Gravitational tugs from Jupiter prevented material from collecting together to form
a planet
Our Star Sun
The sun does not cool off because energy provided by fusion maintains the pressure.
When the Sun is in Gravitational Equilibrium the downward forces on each layer
are balanced by upward force so the star neither expands nor contracts.
Gravitational contraction Provided the energy that heated the core as Sun was
forming, contraction stopped when fusion began
Solar Wind is a flow of charged particles from the surface of the Sun
Coronal holes are dark areas in an X-ray image of the Sun, it provide a corridor for
charged particles to escape into space, generating the solar wind
Aurorae is formed when the charged particles from the solar wind have been trapped
by Earths magnetic field strike upper atmospheres and molecules causing them to
Suns structure Core, Radiation Zone, Convection Zone, Photosphere,
Chromosphere, Corona, Solar Wind (interplanetary medium)
Lecture 18
Fission VS Fusion
Fission -> Big nucleus splits into smaller pieces (Nuclear power plants)
Fusion -> Small nuclei stick together to make a bigger one (Sun, stars)
Sun releases energy by fusing four hydrogen nuclei into one helium nucleus
Hydrogen Fusion by the Proton-Proton Chain, it is how hydrogen fuses into helium
in Sun
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