Well done Tommy, I think you are correct in your assumptions. The sun/stars generate sunshine by nuclear fissioning of matter or anti-matter and over centuries lose weight and gradually fade to red dwarfs. Where has all that energy gone? Between the stars is a border where the incoming starlight balances the outgoing sunlight so in fact the energy must be going its own systems planets moons and asteroids of course. So what are the planets doing with the energy ? Well we are not getting hotter so the inner core must be building up more complex molecules of matter and pushing them upwards into the lava which erupts in volcanoes and builds up the planet.
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