Romulans are notoriously paranoid. They don't trust easily. Two, how many Romulans knew of the possibility of their star exploding? Three, how selfish is leadership going to be about this, if they even have established leadership again that can coordinate.
If Picard knows about it and Utopia Planetia is building an evacuation fleet, I expect the entire planet knows. I just doubt anyone on Romulus is going to sit on the supernova. It stops being political and starts being about your family, your friends, their families, and so on.
Assumption.
I am not a physicist, but since we don't know the exact nature of the explosion but we know it didn't entirely annihilate the planet, in my head I rationalize it as more of a shaped charge explosion.
At least as far as this episode goes, it still has Syracuse written on the neck and Syracuse's registry on the nacelles.
It's also an assumption to think the supernova and evacuation would not be public knowledge to all Romulans.
Probably, because you wouldn’t want citizens in some sort of a panic.
One does not need to be a physicist know that the moon exploding like Praxis did will be an extinction level event for the planet below. Whoever survived on Praxis likely did not live long.
Was this visible in the episodes?
Indeed but the top down, centralized power structure of the Romulan Empire would imply control of information and limiting public knowledge.
I didn't say anyone survived on Praxis. Since we don't know how far Praxis was from Kronos though, why the assumption that it would be an extinction level event, especially in the 23rd century?
Time frame doesn't matter. A moon exploding like that with a shockwave that tossed the Excelsior around like a toy. Most of the moon was gone. All of that matter had to go somewhere, and the planet below is most likely a target given the moon probably exploded in all directions except for the chunk that remained. That kind of mass raining down on Kronos is going to be an extinction level event, plus the shockwave which will do even more damage. Reduced moon mass will affect the moon's gravitational pull on the planet below which means damage to Kronos oceans and ecosystems.
Fair enough, it's Star Trek, I can roll with a BS shockwave.According to the dialog of the movie, it was a subspace shockwave that hit Excelsior, which removes its behavior from the realm of physics to the realm of what ever the FX artists think is cool...
What about all of that mass raining down on Kronos? 
Well, since we're talking subspace—and since the shockwave reached the Excelsior at FTL speed—I'd say the bulk of the moon's material was accelerated to warp speed by the explosion and ejected from the star system. Fortunately for Kronos, the direction of the blast was away from the planet and less than a tithe of the material remained to impact the homeworld's atmosphere.Fair enough, it's Star Trek, I can roll with a BS shockwave.
With reduced moon mass, won't that mean less tidal forces on Kronos, causing devastating effects on the oceans and ecosystems? Lemme guess: they warp in a new moon and warp out the broken one?Well, since we're talking subspace—and since the shockwave reached the Excelsior at FTL speed—I'd say the bulk of the moon's material was accelerated to warp speed by the explosion and ejected from the star system. Fortunately for Kronos, the direction of the blast was away from the planet and less than a tithe of the material remained to impact the homeworld's atmosphere.
How's that for a bit of BS that fits what we were shown in the movie.
