Re: Where the Sun to go Nova, what would the effects be on Earth?

Thanks for your interesting question - you're right to say that the Sun's 
low mass (remember it's small as stars go) prevents it going nova. I like 
the thought experiment, so let's see;

The first thing to say in response to your question is that there really 
would be a pressure wave! We can see evidence for that in other stars 
which have gone supernova, for example on the HST image  here, 
which is a close up of the Cygnus loop - an expanding supernova 
remnant.

These shockwaves slam into surrounding material and excite the atoms 
there, which is what produces the glow. They move incredibly quickly - 
with current telescopes we can watch them expand! For example,  this image, 
taken with the Hubble Space Telescope provides a view of our nearest 
recent supernova, 1987A in the Large Magellenic Cloud.

They move at about 1/10 the speed of light, so would take 80 minutes to 
reach the Earth from the Sun; and would certainly be powerful enough to 
rip the planet apart. 

There's one important caveat - there have been reports of planets orbiting 
pulsars, which are believed to be created in supernova explosions. It's 
believed to be unlikely that planets survived the explosion, so these may 
have formed from the debris left by the explosion.