Illuminated artificially, the colors are caused by layers of bacteria that grow in the hot spring. Steam rises off the spring, heated by a magma chamber deep underneath known as the Yellowstone hotspot. Unrelated and far in the distance, the central band of our Milky Way Galaxy arches high overhead, a band lit by billions of stars. The above picture is a 16-image panorama taken late last month. If the Yellowstone hotspot causes another supervolcanic eruption as it did 640,000 years ago, a large part of North America would be affected.