Main sequence stars turn into red giants towards the end of their lives, as the hydrogen fuel gets used up.
red
the color of the star indicates how hot the star is
no, it isn't a star, it's gas and dust flying across the sky.
A blue star is a star on the main sequence and thus not dying. Actually, blue stars are fairly new, while red ones are generally older (not necessarily/ entirely true). This is the result of a...