(The beauty of x-rays is that they blast right through materials that visible light bounces off of), such as skin, but they can be stopped if a material is dense enough, such as metal or bone.

И еще, скажите, пожалуйста, кто такие auroras в данном контексте.

Most of the planet is dark, because Earth's relatively thick atmosphere does a stellar job of absorbing x-rays. That bright spot near the North Pole is where auroras are glowing, not just as curtains of visible light, but also as swirls of x-rays.

Полярное сияние (поскольку бывает и на южном полюсе)