Ryan Génier from Kitchener, Ontario, Canada Emission nebula Sharpless 2–119 in Cygnus is also known as the Clamshell Nebula. Its ring-like appearance is thanks to the shell of ionized gas — called a Strömgren sphere — surrounding an association of hot, massive stars. (The Rosette Nebula consists of a similar set of features.) This imagerContinue reading "A clam in Cygnus"