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Planetary nebula Abell 33, optical image. This expanding glowing shell of gas is known as a planetary nebula. A planetary nebula forms when changes in a star near the end of its life causes its outer layers to be blown violently outwards. Here, the planetary nebula has, by chance, aligned with a foreground star (lower right). Abell 33 is around 2500 light years from Earth, in the constellation of Hydra. This image was obtained with the FORS2 (Focal Reducer and Low Dispersion Spectrograph) instrument on the ESO's Very Large Telescope (VLT) in Chile. Image released in April 2014. (KEYSTONE/SCIENCE PHOTO LIBRARY/EUROPEAN SOUTHERN OBSERVATORY/SCIENCE PHOTO LIBRARY)