"Ceti Alpha VI exploded, six months after we were left here."
"The shockwave shifted the orbit of this planet, and laid everything waste."
Now, I have, for the time being, dismissed this:

...as the cause of said explosion.
Anyone else got any ideas as to what in the Trek universe would obliterate a planet in such a fashion that the resulting shockwave can shift the orbit of a nearby planet?
Yeah yeah, I know...it's a plot device. Humor me with suspension of disbelief.

