Instead of using the science packs for research you can now melt these into molten science fluid which then again can be burnt in a new refinery. For every burn cycle the map will enable peaceful mode for 1 minute. The peace will continue as long as you can sustain this production cycle.
Enemy expansion is unaffected. Any enemies that have already spawned will remain rogue and may still attack your factory.

The idea is that servers that are running 24/7 with auto_pause = false will have some control over enemy attacks, even when no players are online. So, in the event of a planned absence from Factorio, one can prioritize molten science production and rest assured that the factory will remain intact.

By default the peaceful mode will only be triggered when the last player disconnects from the server. There is also a setting that allows this functionality to work when players are online.