As a noun protostar
is a collection of gas and dust in space with high temperature that usually grows to the point of beginning nuclear fusion and becoming a star.
As an adjective protostellar is
of or pertaining to a protostar.
protostar
English
Noun
(
en noun)
(star) A collection of gas and dust in space with high temperature that usually grows to the point of beginning nuclear fusion and becoming a star.
protostellar
English
Adjective
(-)
(astronomy) Of or pertaining to a protostar.