Portal:Radiation astronomy/Image/16

This composite image contains the first picture of the Earth in X-rays, taken in March 1996, with the orbiting Polar satellite. The area of brightest X-ray emission is red. Such X-rays are not dangerous because they are absorbed by lower parts of the Earth's atmosphere. Credit: Polar, PIXIE, NASA. (The caption and image are from the Astronomy Picture of the Day for December 30, 1996.)