The Sun impresses me. So much energy to dish out, so little of that is taken by planet Earth yet it helped yield and maintain life. Now what will happen when that energy is taken away ...

The sun will destroy the earth long before it stops providing energy.

Why would the sun’s energy be taken away?

It's the impending and inevitable heat death of the universe... several billions of years away...

Our nearest star, Sol, will grow cold well before then.

But even that is estimated to take trillions of years after it runs out of hydrogen for fusion.

I think you're off by about 90 orders of magnitude for the actual heat death

We still have our core

There may be rogue planets out there sustaining life far from any star..

There is. They had a civilization long ago, but now they're down to a small village and only have a radio that they use once every 1000 years.

I managed to talk to them a few years back on my ham. They asked me to send them energy, I told them we'd need to figure out fusion energy first and that we'd get back to them next millenium.