It’s cold out. And our century-old way of staying warm — down jackets — may have just met its match. A new study found that textiles that mimic polar bear fur may be better at keeping us warm than down jackets, not to mention less bulky. In the study, published Dec. 21 in the journal Science, researchers in China tested a fiber modeled off of polar bear fur. Polar bears stay warm in arctic temperatures thanks to the unique structure of their fur, the researchers said. Each strand of polar bear fur contains tiny air pockets that trap heat and prevent it from escaping. The porous core is then su…