Here
is a YPOP activity to measure the rotation rate of the
Sun.
Here
is a YPOP activity to measure the rotation rate of the
Sun.more basic properties of the Sun: http://super.colorado.edu/~astr1120/l3S1.htm
The Sun, like all normal stars, can be described as a hot ball of gas. The size of the star is determined by gravity pulling in on the star and trying to make it smaller balancing with the pressure from the hot gas trying to push out and make it larger. This process is called hydrostatic equilibrium.
figure from Arny, "Explorations: An Introduction to Astronomy" (Dushkin/McGraw-Hill, 1998).
figure from Arny, "Explorations: An Introduction to Astronomy" (Dushkin/McGraw-Hill, 1998).
a little more detail on the layers: http://super.colorado.edu/~astr1120/l3S3.htm
Energy flows from high to low energy regions (heat from hot to cold). The center is very hot and dense so energy flows out from there.
CORE = nuclear "furnace" producing high energy photons,
temperature = 15 million K from nuclear fusion of Hydrogen into
Helium (more on this later).
High energy photons are absorbed by the soup of protons and reemitted. The energy is transported by electromagnetic radiation.
(It takes up to million years for a photon from the core to get to
the surface !!)
Closer to the surface colder gas absorbs photons.
The energy is now transported by motion of the gas. The hot gas (less dense) rises and the cooler gas sinks.
This produces convection cells, visible on the surface as granulation.
Here are some relevant links describing this:
The surface of the sun is a thin (500 km) layer of low density and cold (6,000 K) gas.
more photosphere information: http://csep10.phys.utk.edu/astr162/lect/sun/photosphere.html
Above the surface lies the lower atmosphere of the sun: hot (50,000 K), 1,500 km thick low density gas.
Why is it so hot? probably magnetic field heating of charged particles
more chromosphere information: http://csep10.phys.utk.edu/astr162/lect/sun/chromosphere.html
The upper atmosphere: extremely hot (1 million K), 200,000 km thick very low density ionized gas (irregular and changing in shape)
more corona information: http://csep10.phys.utk.edu/astr162/lect/sun/corona.html
If the sun's energy came from something like coal burning => enough mass for a few thousand years only
If the sun's energy came from gravitational collapse => no equilibrium, should shrink, and would last for 10 million years
But, the Sun is at least billions of years old (from fossil record on Earth)
So the only logical source of energy is NUCLEAR FUSION (E = m c 2)
more on fusion: http://csep10.phys.utk.edu/astr162/lect/energy/mass-energy.html
The nucleus consists of protons and neutrons held together by nuclear force (strong, short ranged, attractive)
The size of the nucleus comes from a balance between repulsive electric and attractive nuclear forces.
more information: http://csep10.phys.utk.edu/astr162/lect/energy/reactions.html
Depending on how full the "bag" nucleus is (# of protons + # of neutrons), energy will be released when:
small nuclei merge = FUSIONlarge nuclei split = FISSION
Energy is in the form of binding energy from missing mass
|
http://super.colorado.edu/~astr1120/l3S4.htm
http://csep10.phys.utk.edu/astr162/lect/energy/bindingE.html
In the core we have a soup of protons (plasma) at very high temperature and density. The protons collide frequently and violently, sometimes fusing and initiating nuclear chain reactions. The sun appears to get most energy from a proton-proton chain where hydrogen if fused into helium.
http://csep10.phys.utk.edu/astr162/lect/energy/ppchain.html
The sun changes on a daily basis as well as over longer periods of
time.
Here is
an activity developed by YPOP to help you understand the cycles
of the Sun.
neat activities: http://www.lmsal.com/YPOP/Classroom/