PBS science series since 1974 (4)
I believe the answer is:
nova
'pbs science series since 1974' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nova that I've seen before include "Star that suddenly increases in brightness" , "Exploding star" , "Suddenly expanding star" , "Canadian province" , "A new flaring star" .)