TRAPPIST-1 is described as "Jupiter-sized" (comparable radius), although at 8% of the Sun's mass, must be on the order of 100x greater (Jupiter : Sun is about 1 : 1000). This seems paradoxical and raises several questions.
Since Jupiter is thought to be mostly hydrogen and other light gasses, and as a star, TRAPPIST-1 must be mostly hydrogen (it is fusing hydrogen into helium, isn't it?), how can it be so much hotter and denser at the same time? Shouldn't the high temperature keep the density down?
Jupiter has been described as a "failed star" - too small to produce the conditions necessary for nuclear fusion to occur. Does TRAPPIST-1 offer any useful insight as to where that threshold lies - how big is big enough to get the process started? Just how close is Jupiter to that threshold, anyway?
Could it just be that some of the facts are wrong, and when corrected, there is really no paradox at all?