This system is astronomically energetic! (5)

I believe the answer is:

solar

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'this system' is the definition.
(solar system is a kind of system)

I cannot understand how the remainder of the clue works.

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(Other definitions for solar that I've seen before include "room" , "Powered by the sun" , "Using the sun's energy" , "Particular star's" , "Relating to our star" .)

I've seen this clue in the Evening Standard.

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