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Lecture

AST101H1 Lecture Notes - Solar Dynamics Observatory, Helioseismology, Hydrostatic Equilibrium


Department
Astronomy & Astrophysics
Course Code
AST101H1
Professor
Michael Reid

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AST101: The Sun and its Neighbors Lecture
November 20, 2012
THE SUN
- the sun is about the mass of 1047 Jupiters
- Solar Dynamics Observatory
- the sun is one of the most well-understood things in science
- the sun is fairly simple: it's a big sphere
- sunspots are on the sun --> the earth is as big as one of these
- what is the sun made of?
!- mainly Hydrogen --> ionized gas (plasma)
!- also Helium
- inside, the sun is in hydrostatic balance: pressure from heat generation pushes
outward and gravity pulls inward
- the core of the sun is where the energy is being produced
- also has a radiative zone and convective zone, named after the ways they spread
energy
- How can we know what's going on inside the sun?
!- helioseismology ("sun quakes") - the sun vibrates in many different ways, and
the amount of vibrating that it does can tell us what is inside the sun
!- neutrinos - "neutrinos, they are very small. They have no charge and have no
mass. And do not interact at all. The earth is just a silly ball. To them, through which
they simply pass, like dust-maids through a drafty hall or photons through a sheet of
glass"
!- they do, however, have a very small mass, and they do interact, but only via the
weak nuclear force and gravity
!- neutrinos come almost directly to us from the core of the sun
!- plasmas are opaque - they block light pretty well - this is because of the free
electrons, which absorbs light and re-emits it in another direction
!- a neutrino will just go through
!- light made in the core of the sun takes thousands of years to work its way out
!- surface convection patterns: hot gas rises while cooler gas descends around it
!- at the top of convection cells, we can see brighter write spots - this is called
solar granulation
!- based on all of these ways of probing the sun, we can build a model of what's
inside
- layers of the sun:
!- core (where fusion reactions occur)
!- radiation zone (energy is radiated outwards)
!- convection zone (convection happens)
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