Translation of "Dwarf" in Japanese

"Mum, how big is a brown dwarf actually?" "Brown dwarfs are about as big as Jupiter but have many times its mass."

「ママ、褐色矮星ってどれくらいの大きさなの？」「褐色矮星はね、木星とおんなじくらい。でも重さは木星よりずうっと重たいのよ」