October 10, 2013.
Lecture 10 - The solar spectrum—continuous part
Nuclear fusion keeps the Sun’s core at about 15 million K
Fusion: sticking nuclear particles together
o Particles have to be moving super fast to fuse; temperature is really a measure of
how quickly particles are moving
How hot is the sun?
o 6000 K, 10 000 K, 1 000 000 K, or 15 000 000 K
o All of the above depending on core, outer layer, etc.
The solar thermostat stabilizes energy production in the core
o A slight drop in core temperature leads to a large decrease in the fusion rate that
lowers the core pressure causing the core to contract and heat up thereby
restoring the fusion rate to normal
If the Sun’s core got a little hotter, what would happen?
o The fusion rate would increase until the core expanded, then it would slow down
We can see the sun because it EMITS light
o Whereas the moon REFLECTS light