The Sun: 

proper name =  Sol 	(as in "the Solar System")


1 solar radius = 109 Earth radii

(Jupiter radius = 11 Earth radii)


Temperature at surface = 5800 K = 11,000° F,
	about as hot as a lightning bolt.

Temperature at center (core) = 15 million K



Solar filters: always look like mirrors, and always go in front of telescope tube.

NEVER in front of eyepiece: these are DANGEROUS and should be destroyed!


























Sunspots: caused by strong magnetic fields on solar surface (photosphere)



Solar cycle: sunspots come and go over an 11-year cycle

We are currently coming down from a Solar maximum, in 1999-2001.

This was "the real Y2K problem", as solar flares and coronal mass ejections (CMEs)
are most common during Solar max.




































The four known forces of nature:
1) Gravity: 								- Always attracts
2) Electromagnetism (electricity + magnetism + light): 		- Can attract or repel
									   (Opposites attract)
3) Weak nuclear force (accumulates in heavy nuclei, 
e.g. uranium or plutonium, making				- Repels, but is weak
them split, causing radioactivity)

4) Strong nuclear force: binds nuclei together, 			- Attracts, but only
despite the like charges of their protons			    inside nuclei


Nuclear physics for beginners:

The Sun generates energy by nuclear fusion:

By joining atomic nuclei together at high temperature, in its core.

Hydrogen nucleus: 	mass = 1.007825 amu
Helium nucleus:	mass = 4.002603 amu
	(1 amu = 1 atomic mass unit = 1.6605402 x 10-27 kg)

Notice that:
4 x 1.007825 amu = 4.0313 amu > 4.002603 amu,

So:
4 x mass(hydrogen) > m(helium)

So: 4 hydrogens become 1 helium + energy, since E = mc2.



This is unlike how a commercial nuclear reactor works, by nuclear fission,
which liberates energy by splitting large nuclei, such as uranium or plutonium.



Nuclear weapons: 

"atom" bombs, used on Hiroshima and Nagasaki in 1945, used fission;

"hydrogen" bombs, or thermonuclear weapons 
(1000 times more powerful, first tested in 1952), use fusion 
(with a fission bomb to trigger fusion reactions in hydrogen).


Let us hope they will never be used again!