Have any galaxies actually faded into darkness before? Considering our galaxy is basically the same age as the universe I find it hard to believe any galaxy has just run out of energy and gone dark.

I suppose you could interpret it as the galaxy leaving the observable universe, but that doesn’t have the same meaning to me.

[–] Amicitas@lemmy.world 19 points 3 weeks ago

Yes absolutely. A galaxy is considered 'dead' after it can no longer generate new stars. Here are a couple of articles:

Death of giant galaxies spreads from the core: https://esahubble.org/news/heic1508/

A galaxy that suddenly stopped forming new stars more than 13 billion years ago has been observed by astronomers: https://www.cam.ac.uk/research/news/astronomers-spot-oldest-dead-galaxy-yet-observed