Pictures of the month
Some 14 h of observations using the Chandra X-ray observatory produced these maps of the heavy elements ejected from a supernova explosion. These images of the supernova remnant Cassiopeia A show (left to right) the distribution of silicon, calcium and iron in the matter thrown out from the exploded star. The shell is about 10 light-years in diameter and has a temperature of about 50 million degrees.