Galactic ghosts

Eight shadowy galaxies that were briefly lit up by a powerful blast of energy

Each of these wispy celestial objects is a galaxy photographed by the Hubble Space Telescope. Most of the filaments that surround them, which show up mainly in green, were practically invisible until the energetic quasar that surrounds the supermassive black hole in their host galaxy lit them up with an extremely powerful blast of radiation. This caused elements in the filaments, including oxygen, helium and sulphur, to absorb the energy and release it gradually as light. Each element glows in a different colour and green, the most abundant colour in these images, is ionised oxygen. The process is called photoionisation and the filaments will glow for many thousands of years after having been ionised – although this period is just a blink of an eye on a cosmological scale. The…

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All About Space Tour of the Universe (Digital) - 1 Issue, All About Space Tour of the Universe 4th Edition

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