Questions about stars in space?

>What is the temperature of an average star?

The temperature of the inside of a star often goes up to millions of degrees kelvin. When people talk about the temperature of a star, they usually mean the temperature of the star's surface. The surface temperature of stars can range from as little as 3000 kelvin (red dwarf stars) to 50000 kelvin (blue supergiant stars). However, most of the stars in the Universe are relatively small (smaller than our own Sun), so I would say the average temperature is probably around 5000 or 6000 degrees kelvin. However I can't find any actual data on this subject.

>How big is an average star?

Again, most stars are relatively small stars, however the largest stars (such as red giants) do get VERY large sometimes, so the average diameter (distance from side to side) of stars is probably something like 1000000 (one million) kilometers or thereabouts. Again, I can't find any actual data, so that's just a guess.

>Are most stars bigger than the sun?

No. Over half the stars in the Universe are red dwarf stars, which are smaller than the Sun. There are also quite a few small orange stars, yellow stars and white dwarfs which are also smaller than the Sun. Probably something like 70% or 80% of all stars are smaller than the Sun.

>How did stars form?

Stars form out of clouds of gas (mostly hydrogen) floating in space, as they pull themselves together under their own gravity to the point where they can start undergoing nuclear fusion (which is what lights up most stars, such as the Sun). These gas clouds usually come from the debris left over from the explosions of giant stars earlier in the lifetime of the Universe, although some of them also form out of gas that was just floating in space ever since shortly after the Big Bang. The first set of giant stars that existed in the past all came from gas that was floating in space; the gas was much denser then than it is now, because the Universe was smaller and there were no stars already in existence at that time.

>What are the stages of a star?

This depends on the type of star. The life cycle of a standard star such as the Sun is not the same as the life cycle of a giant star or a red dwarf star. You can read more about life cycles of stars here:

http://imagine.gsfc.nasa.gov/docs/teachers/lifecyc...

>Can a star die? How?

Stars are not living things and so they cannot actually die. However, people often think of a star 'dying' if it goes through a nova.

Stars shine because they fuse hydrogen atoms together into helium atoms, a process which releases light and heat. It is easier to fuse hydrogen atoms than it is to fuse helium atoms (that is to say, it requires less pressure and heat to do so). A star like our Sun goes on fusing hydrogen during its life cycle, but as time passes there is less and less hydrogen available to fuse (because it is being used up and turned into helium). Since less hydrogen is fusing, the star has less energy to hold it out, and so it slowly becomes smaller, denser and hotter. After a few billion years (or a few million years, if it is a large enough star), the pressure and heat inside reach the point where it suddenly becomes possible to fuse helium atoms as well. This sets off a chain reaction of fusing helium atoms, which causes the star to expand enormously. A main sequence star like our Sun expands into a red giant star, then blows away the top layers of itself into space, and the rest contracts and forms a white dwarf star (which no longer fuses any atoms at all, and emits light only because it is still hot). A larger white or blue star may be large enough that the helium reaction causes it to explode and blow away just about all its mass, in which case the remaining mass may crush itself into a neutron star or a black hole. A white dwarf, neutron star or black hole could therefore be thought of as the star after it 'dies'. You can read more about them here:

http://simple.wikipedia.org/wiki/White_dwarf

http://simple.wikipedia.org/wiki/Neutron_star

http://simple.wikipedia.org/wiki/Black_hole

You could write a book to answer these questions. This is far beyond the scope of this forum.

Most stars are in fact smaller than the sun, a perfectly ordinary G class star.