The life cycle of a star
In clouds of dust and gas called nebula, stars are born. The Sun in our Solar System was born in a nebula, estimated at 5 billion years ago. The gas is mostly hydrogen and some helium. It begins to condense (pull together) to form a protostar which is not at all stable. As the matter condenses, it becomes “hotter.”
If the matter does not heat to a critical stage, the protostar does not develop further into a star. Instead it becomes a brown dwarf, something that is not too big, not too hot, not too bright. Stars tend to born as “twins” so that one may develop into a star and the other a brown dwarf. Read more
