I just did some googling. Yup, appears you're correct. About 80 Jupiter masses is what's required to ignite into a star. Huh. Cool, learned something. Which is: don't trust Arthur C. Clarke *evil grin*.
http://www.badastronomy.com/bad/misc/jupiter_galileo.html
Qwinn
Bad Astronomy is an A-OK site, I highly recommend. :)