Answered

why are telescopes that detect non- optical radiation useful for studying objects in space



Answer :

AL2006

Because many objects in space don't radiate any optical (visible) radiation at all.
And other objects, like stars, radiate a lot of invisible radiation in addition to the
visible light from them.  So the ability to detect and measure invisible radiation
makes it possible to learn a lot more about objects in space than we could if
we could only use their visible light.