The speed of the Hobus supernova shockwave

This is from a reply comment under a YouTube video.

The Hobus star was not the star of the system where Romulus and Remus were, but a fair distance away. This means, that the Hobus star could have gone nova at lightspeed, but the shockwave slowed down as it went wider.

If a rock falls into a large body of water, the waves in the water will slow down over time.

I looked at one of the Destruction of Romulus videos, where Spock explains, that the nova threatened to destroy the entire galaxy.

As the nova went off, Spock's narrative can be followed in linear order: the Vulcans and Spock then outfitted starship Jellyfish (already under construction), specialised from the outset to carry Red Matter, and Spock went on route to save Romulus, but was late.

So there was a timespan between when the nova went off, and when it reached Romulus, but not enough time.

I traced my finger on the 360p video screen across Romulus at the on-screen speed of the shockwave as it crossed 2x the approximate radius of Romulus (let's compare with Earth's 12,756.274 km), and used a stopper in conjunction, because I managed to count to three in less than three seconds.

The approximate time of the shockwave crossing the width of Romulus was just 2 seconds (tops), which makes the speed of the shockwave at _ca_ 6378.137 km/s, which is hardly lightspeed at that point. I did calculate the speed of the shockwave in the Romulan star system to be about 2.17% the speed of light.

At this point, Spock had not yet subdued the nova. While he had his Red Matter black hole empty most of the energy of the nova, he probably could not prevent the rest of the greatly-weakened shockwave from moving on.

Spock indeed saved the galaxy, but the shockwave would still dissipate within the space of the Romulan Star Empire, still affecting many systems in its way, and damaging habitable planets.