This composite image from the Hubble Space Telescope’s Advanced Camera for Surveys and its Wide Field Camera 3 shows a huge cluster of galaxies some six billion light years away known as PSZ23 G138.61-10.84. The image is from an observing programme called the Reionization Lensing Cluster Survey, or RELICS. The RELICS project has studied 41 galaxy clusters to help locate the brightest distant galaxies for follow-on observations by the James Webb Space Telescope, scheduled for launch in 2020.
The Atacama Large Millimetre/submillimetre Array (ALMA) has been used to detect the most distant clouds of star-forming gas yet found in normal galaxies in the early universe. The new observations allow astronomers to start to see how the first galaxies were built up and how they cleared the cosmic fog during the era of reionisation.
Astronomers studying the distant universe have found that small star-forming galaxies were abundant when the universe was only 800 million years old, a few percent of its present age. The results suggest that the earliest galaxies, which illuminated and ionized the universe, formed at even earlier times.