Residing behind a galaxy supercluster called Abell 2744, the JD1 galaxy is gravitationally lensed and displays three images.
The first billion years of the Universe’s life were a crucial period in its evolution.
After the Big Bang, approximately 13.8 billion years ago, the early Universe expanded and cooled sufficiently for hydrogen atoms to form.
Hydrogen atoms absorb ultraviolet photons from young stars; however, until the birth of the first stars and galaxies, the Universe became dark and entered a period known as the cosmic dark ages.
The appearance of the first stars and galaxies a few hundred million years later bathed the Universe in energetic ultraviolet light which began burning, or ionizing, the hydrogen fog. That, in turn, enabled photons to travel through space, rendering the Universe transparent.
Determining the types of galaxies that dominated that era — dubbed the epoch of reionization — is a major goal in astronomy today, but until the development of the NASA/ESA/CSA James Webb Space Telescope, astronomers lacked the sensitive infrared instruments required to study the first generation of galaxies.
“Most of the galaxies found with Webb so far are bright galaxies that are rare and not thought to be particularly representative of the young galaxies that populated the early Universe,” said Dr. Guido Roberts-Borsani, a postdoctoral researcher at the University of California, Los Angeles.
“As such, while important, they are not thought to be the main agents that burned through all of that hydrogen fog.”
“Ultra-faint galaxies such as JD1, on the other hand, are far more numerous, which is why we believe they are more representative of the galaxies that conducted the reionization process, allowing ultraviolet light to travel unimpeded through space and time.”
First discovered in 2014, JD1 is located behind the huge galaxy cluster Abell 2744.
Abell 2744 is about 4 billion light-years away, some 350 million light-years across, and…
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