PBS science series (4)
I believe the answer is:
nova
'pbs science series' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for nova that I've seen before include "Exploding star" , "A new flaring star" , "Star that becomes much brighter for short time" , "Newly bright star" , "Star that suddenly becomes brighter for a time" .)