Hi, water water everywhere--but where did it come from? Our solar system is made of star stuff, did our water form during a super nova? Can H₂O exist in stars?

No, H₂O cannot exist in stars, but H and O separately can. Hydrogen is the basic building material of the universe, created in the Big Bang. Oxygen is created by nuclear reactions in stars. If you put H and O together in the cold of space, you get H₂O. There are enormous amounts of water in space. In fact, nearly all of the oxygen in space is in the form of water or carbon monoxide. Similarly, most the carbon and nitrogen in space are also in their most hydrogenated forms: methane (CH₄) and ammonia (NH₃).