you guys are getting primordial nebulae confused with stellar nebulae. the horse head nebula is a stellar nursery. it was once a vast field of gases but thru gravitational eddies, stars began to form. there is no evidence suggesting the horse head nebular was created by stars since the nebula itself is millions of times larger than our solar system. if you look at the picture of the horse head nebula, the points of light you see coming out the nebula are supermassive stars illuminating their stellar cocoon. a shroud of gas surrounding the newly born star which (due to the abundance of gas in the area) is several times larger than our entire solar system. the inside diameter of the cocoon alone is dozens of times the size of our solar system. compared to stellar nubulae which are created out of the dust of a nova'd star or the cast-off shroud of one. these nebulae are many orders of magnitude smaller than primordial nebulae, like the horse head nebula. the eagle nebula is another example of this. the cat's eye nebula is derived from a star gone nova and is many times smaller than the horse head or eagle nebula. stars can and do reform out of their own novas. it is believed that for our solar system to have the distrobution of elements it has now, our sun is at least in its 3rd generation. in other words, it has gone nova and reformed 3 times. this happens regularly throughout the universe. large nebulae can be so large that it is likely the bulk of their gas wont be concentrated in stars for billions of years. if you go on wikipedia and look at the pic of the horseh ead nebula, the points of light you see (that i referenced earlier) often contain groups of hundreds of stars. the horse head nebula is NOT small and cannot be compared in side to the cats eye nebula and other nebulae on that order of magnitude.
in reference to an earlier post, a planet that is cast into space would not lose its atmosphere simply becaus eit wasnt around a star anymore. internal heat generation and volcanic activity would not stop either. however, due to the lack of sunlight, the surface of the planet would indeed freeze and be uninhabitable. the end is the same, but the means are quite different.
also, binary star systems are VERY stable. the only disadvantage to being in a binary star system is that solar radiation is effectively doubled and the safe distance from the stars would also double depending on the types of stars in the system. for example, if one star were 'feeding' off the other (i wont go further into detail on these setups unless i need to right now), the stellar ribbon or 'funnel' would emit much more radiation due to the transit of stellar material from one star to the other. also, is a star is feeding off one it is likely because it is old and its fuel is running out. stars in this stage of life are usually hazardous and emitting large amounts of xrays and other radiation which would be bad for life.
