Isn't that close to the size of our sun? In any case 10 times the size of Jupiter is a big-ass planet.
There is some info out there about how much bigger Jupiter would have to be to turn into a star.
Roughly speaking, Jupiter is 300 times the mass of the Earth. The sun is 300,000 times the mass of the Earth, or about 1,000 times the mass of Jupiter.
As best I recall, stars don't form unless the mass is at least 0.1 solar masses (and maybe even bigger), so a minimum stellar mass would be about 30,000 times the mass of the earth, which would be 10 times larger than a planet with a mass of ten Jupiters.....
That makes Jupiter too small to be a star by a factor of about 100....
Objects that are slightly too small to initiate fusion reactions and become full fledged stars are called "brown Dwarfs"... a google search will probably tell much more than I can about them....
Sloppy journalism here. What is meant? 10 times the MASS? 10 times the DIAMETER? I'm guessing mass; diameter wouldn't probably reach 10 times Jupiter's without increasing the mass past the "brown dwarf" threshold.
Excluding the Sun, Jupiter contains the majority of known mass in the Solar System. But it still is way too small (low-mass) to have initiated fusion in its core: it's only .001 solar masses! The estimates vary; I've heard that Jupiter would have to be around 80 times its current mass to "turn on" as a very small red dwarf. Anything 10-70 Jupiter masses would be a "brown dwarf", glowing in the visible spectrum from residual heat.