Astronomy has a way of getting past you! Tuesday I put up my new article for Wednesday. And - lo and behold! - I read on Wednesday night that an even smaller star than the one I'd named had been discovered.
I'll be amending the article later, but meanwhile I'll tell you that now the smallest star ever measured is
2MASS J05233822-1403022. It was discovered in the 2-micron All Sky Survey data. It's actually smaller than Jupiter, but it has more mass than the planet. Its temperature is 1,800° C. That's hot in our terms, but not so hot for a star. The Sun's temperature is 5,600°. 2MASS J05233822-1403022 is about forty light years away.