In September 2019, the Hubble team announced a social media initiative to celebrate three decades of success in discoveries with the NASA/ESA Hubble Space Telescope. The campaign showcased 30 hidden gems from the Hubble image archive. The 12 images that received the most likes were compiled to produce a special 30th Anniversary Calendar for 2020 (.pdf file, high-resolution print-ready .pdf file). The cover page of the Hubble’s Hidden Gems 2020 Calendar....