Can you explain the proccess of star formation, and also do we know of any stars that arent made of hydrogen and helium?

Clouds of hydrogen, and perhaps a few other elements, condense due to their own gravity. (Look for pics of the Orion and Eagle nebulae - pretty cool.)

The gas coalesces, and the gravitational attraction at the center of the cloud collects more and more gas, compressing and heating the core.

Over time, as more mass collects - and more is attracted due to the growing gravitational pull - the heat and pressure on the core grows to the point of sparking nuclear fusion - combining hydrogen into helium - and the star is born.

Our sun was formed this way, and at the center is a growing core of helium - the product of hydrogen fusion.

While it's *possible* for a star to be made out of materials other than hydrogen/helium, there simply isn't enough concentrations of matter for this to happen. Hydrogen is basically the *easiest* element to fuse, and it releases the most energy per unit of mass; as you move up the scale - fusing helium into carbon, carbon into calcium, etc. - you need much higher pressures and heat, and a lot of material providing that pressure... while it woudl be *possible* to gather that together - it just naturally wouldn't occur; hydrogen is 91% of the content of the universe, with all the other elements forming the rest... statistically - it has about a zero chance of happening.

Hydrogen and Helium fuse under pressure and release energy.

Helium fusion results in Iron as the "ash" - elements up to Iron are fairly rare and never in big enough amounts to make a star.

Iron will fuse under great pressure - this absorbs energy and Iron fusion is the engine of Super Nova's.

Most if not all stars are made out of Hydrogen.

The few that burn helium do so for a very short period of time.

As far as we know all main sequence stars are mostly hydrogen and helium, but red giant stars have synthesized other elements such as silicon, oxygen, neon and iron.