... Dubbed a Lyman-alpha blob, an enormous cloud of hydrogen gas spans several hundred thousand light-years in this remarkable image (left), a composite of x-ray, optical, and infrared data from space and ground based observatories. ... This emission nebula on the left is famous partly because it resembles Earth's continent of North America. ... This six month long exposure compresses the time from solstice to solstice (~ December 21, 2008 to June 20, 2009) into a single point of view. ... June . ...