NASA, ESA and the HST Frontier F

A group of international scientists used observations from the Hubble telescope to find more than 250 faint galaxies, many of which were likely formed just 600 to 900 million years after the Big Bang. The images produced by Hubble are pretty spectacular:

Galaxy cluster MACS J0416.1–2403.
NASA, ESA and STScI
Galaxy cluster MACSJ0717.5+3745.
NASA, ESA and STScI
Abell 2744, nicknamed Pandora’s Cluster.
NASA, ESA and STScI

The discovery allows the astronomers a glimpse back in time: NASA explains that it took at least 12 billion years for the galaxies' fading light to reach our telescopes.

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A team of researchers led by Swiss astronomer Hakim Atek suspect that the galaxies were involved in the period known as "reionization," when budding stars began to flood the universe with UV light. Before then, the cosmos were dark. Per NASA:

The team discovered that the accumulated light emitted by these galaxies could have played a major role in one of the most mysterious periods of the universe’s early history—the epoch of reionization. Reionization started when the thick fog of hydrogen gas that cloaked the early universe began to clear. Ultraviolet light was now able to travel over larger distances without being blocked and thus the universe became transparent to ultraviolet light. By observing the ultraviolet light from the galaxies found in this study the astronomers were able to calculate whether these were in fact some of the galaxies involved in the process.

Their findings appear in a paper published in the Astrophysical Journal. 

Danielle Wiener-Bronner is a news reporter.