APOD: 2015 April 12 - Sentinels of the ArcticAstronomy Picture of the Day Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2015 April 12 Explanation: Who guards the north? Judging from the above photograph, possibly giant trees covered in snow and ice. The featured picture was taken a few winters ago in Finnish Lapland w
