Judging from the size diagram, I'm going to estimate it's 1:100th the size of the sun overall. Would we even feel it's warmth?
Mass and luminosity are more important than physical size, though size is a small component of luminosity. Luminosity is mostly related to temperature, which is dependent on the mass and evolution if it is a main sequence star.
Anyway, the Sun is 1000 times the mass of Jupiter, which would make for a pretty dim red star even if fusion could be initiated, and Jupiter is pretty far away, so the effect will be small. I don't have the equation for luminosity and its relationship with mass, evolution, temperature, etc., but even a few degrees will wreck the biosphere.

