Like a ship approaching a distant beacon, astronomers are getting closer and closer to the cosmic dawn, the time in the universe's history when the first stars formed. A team of researchers announced that the Hubble Space Telescope has allowed them to see as far back as a mere 380 million years after the Big Bang -- more than 13.3 billion years ago. That's within striking distance of the first stars, which researchers think were born 200 million years after the universe began.
More remarkable is that the researchers, led by California Institute of Technology astrophysicist Richard Ellis, have imaged not one but seven galaxies from that early cosmic period, dating between 380 million and 600 million years after the Big Bang.
The discovery provides the first census of galaxies from what's known as the epoch of reionization. During this period, which extended from the cosmic dawn to about 1 billion years after the Big Bang, ultraviolet light was breaking down hydrogen into a soup of electrons and protons, making the universe more transparent.
The findings described by Ellis and his colleagues suggest that these first galaxies provided the ultraviolet radiation required to reionize the universe. The researchers conclude that "reionization is an extended process associated with gradual galaxy growth," Ellis said. "Cosmic dawn was likely not a dramatic event."
Until recently, said Harvard astrophysicist Abraham Loeb, "most of the research on the first generation of galaxies was theoretical, but the next decade promises a flood of data." Much of that data will come from the James Webb Space Telescope, scheduled for launch in 2018.
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