Chandra's image of Messier 101, taken in X-ray light, shows the high-energy features of this spiral galaxy. X-rays are generally created in violent and/or high-temperature events. The white dots are X-ray sources that include the remains of exploded stars as well as material colliding at extreme speeds around black holes. The pink and blue colours are emission from million-degree gas and from clusters of massive stars. The pink emission indicates lower-energy X-rays and the blue higher-energy X-rays. One reason astronomers study Messier 101's X-rays is to better understand how black holes grow in spiral galaxies.