I checked the save game and this is a delayed event assigned to Sol (playing as humans), named newfrontiers_disasters.31 . So, I assume it relates to this mod. Personally, if I wanted to play the Exploding Homeworld origin, I'd have chosen it during the civilization creation dialogue. Also, if it is going to randomly assign to the home system, having to deal with it in 2240 is kind of harsh.

Once I finished researching Stellar Anomaly, I got a dialogue about rescuing my own empire; the game asked me, the UNSF, if I wanted to allow refugees from the Sol system to settle in one of my systems. So that was weird. Haven't played through this event before, so don't know if it is further broken after that, but worth noting.

Latest Stellaris w/ all DLC.

My mods installed:
* Planetary Diversity
* Glavius's Ultimate AI
* Planetary Diversity - Exotic Worlds
* All Unique System and Caravaneer Spawns 2.7x
* 2.7+ Machine Shipsets
* Planetary Diversity - More Arcologies
* Real Space 3.6
* Real Space - New Frontiers
* More Events Mod
* Distant Origins