Webster's has the following definitions pertaining to the use of luminary as describing people...

1) a person of intellectual or moral eminence, esp. a person who has attained eminence in his field or is an inspiration to others; a leading light

2) (loosly) any famous person; celebrity

I have never heard luminary used as in the second example. Perhaps, IMHO, this is because luminary implies intellectual or moral brightness and not all stars are all that bright, and moral, well, we won't even go there. Some stars are only stars for a very brief time so luminary seems to overstate it a lot.