Astronomy Use Back at top of this Browser to return to previous position your last page. There are so many stars which can be studied that astronomers have built up a detailed picture of how they believe these fascinating celestial objects 'live' and 'die'.
Stars change considerably with time.
The time it takes for changes to happen is often only measurable in millions of years. This means that astronomers never actually see stars move from one evolutionary phase to the next. This is compensated for by the fact that there are so many stars in the sky, all at different stages in their evolution, which can be studied. It is similar to an extraterrestrial seeing adults, children and babies but not being able to watch them age and grow. From the brief observations the extraterrestrial has made, he must try and deduce the correct sequence of events and the correct place for each type of human on the sequence.