How did the processus of turning persons into constellation or celestial bodies worked in mythology?

I am nearly at the end of my novel about a great,undefeated warrior. I thought that,at the end of his life,he would ask to be transformed into a beautiful comet crossing the nightly sky every now and then(pretty much like his adventurous life).Where this type of things present in mythology or other stories?What would that person had to achieve to obtain such a thing?I just thought this end would suit his deeds...|||The best is to begin with a symbol that can fit as a shape made by several stars. Then you sneak in a God or Goddess to place the heroes essence on those stars.