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This image of Abell 2744 is the first to come from Hubble's Frontier Fields observing programme, which is using the magnifying power of enormous galaxy clusters to peer deep into the distant Universe. Abell 2744, nicknamed Pandora's Cluster, is thought to have a very violent history, having formed from a cosmic pile-up of multiple galaxy clusters. Abell 2744 is the first of six targets for an observing programme known as Frontier Fields. This three-year, 840-orbit programme will yield our deepest views of the Universe to date, using the power of Hubble to explore more distant regions of space than could otherwise be seen, by observing gravitational lensing effects around six different galaxy clusters. Galaxy clusters are so massive that their gravity deflects light passing through them, distorting the images of the distant objects behind them and sometimes magnifying and brightening them in a phenomenon called gravitational lensing. Ideally, astronomers use spectroscopy to determine an object's distance. The further away a galaxy, the more its light has been stretched by the Universe's expansion and we can precisely measure this effect, called the redshift, spectroscopically. But objects found at this early epoch are too dim for astronomers to use spectroscopy. For these fainter objects, astronomers have to rely on a less accurate method that estimates their distance based on their colours.
Image Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI).
Image enhancement: Jean-Baptiste Faure