The story of how stars are born, evolve and die is one of never-ending violence and change, a tale that will be more fully revealed in the spectra taken of stars at many different stages of their lives.
Stars begin to form in the coldest depths of space within huge clouds of interstellar gas and dust.
By taking ultraviolet spectra of starlight shining through these cold gas clouds, scientists hope to understand better the size, density and temperature in these stellar nurseries, which are make up mostly of molecular and atomic hydrogen gas - the universal building blocks. From observations and theoretical calculations, scietists currently believe that through gravitational contraction, a hydrogen gas cloud becomes hot enough to trigger nuclear reactions, thus giving birth to a new star. Once their reserves have been exhausted, the larger stars explode in violent supernovae, and for one brief period outshine all other objects in the galaxy. Eventually, low-mass stars like our Sun end up as these compact white dwarf stars, emmitting most of their dwindling energy resources in the far ultraviolet wavelegth range. By observing these objects, scientists can determine how fast they are cooling, and therefore estimate the death rates of stars similar to the Sun.