For nearly 400 million years in its early history, the universe was very dark until the first star-producing galaxies started to produce ultraviolet light that eventually lighted up the cosmos.

Several hundred thousand years after the Big Bang, the protons and electrons that were scattered in the cosmos started to cool and formed the first atom of hydrogen. The phenomenon eventually resulted in the formation of hydrogen walls and clouds of cosmic dust that absorb ultraviolet radiation. This prevented light from escaping and marked the dark ages of the universe.

After some time, the radiation become strong enough, it reionized the hydrogen, which happens when the photos accumulate enough energy to cause the electrons to break out from the hydrogen atoms, resulting in the  lighting up the formerly dark universe. The radiation that broke the electrons is believed to come from stellar births but astronomers are still unsure of what exactly happened.

"The star forming regions in galaxies are covered with cold gases so the radiation cannot come out. If we can find out how the radiation gets out of the galaxy, we can learn what mechanisms ionized the universe," Sanchayeeta Borthakur, an astronomer from the Johns Hopkins University said.

It appears that a newly discovered galaxy could offer some clues on how the early universe lighted up. Borthakur and colleagues have discovered a densely packed galaxy that reproduces the events that lit up the early universe.

The galaxy called J0921+4509 possesses many of the characteristics that scientists believe would have been needed for lighting up the universe near the beginning of time. It leaks photons with an energy that can ionize hydrogen atoms.  The galaxy also allows over 20 percent of its ultraviolet radiation to seep through the dust clouds causing it to radiate intense levels of ultraviolet light and offering clues to scientist on how the earliest galaxies of the universe may have likely behaved.

Located 2.9 billion light-years away from the Milky Way, the galaxy produces stars in a compact region at a rate comparable with that of the budding galaxies in the earliest time. The galaxy churns out 50 stars with the same mass as the sun per year, which is 33 times more than the number of stars that the Milky Way produces for the same period.

The findings were described in "A local clue to the reionization of the universe, which was published in the journal Science on October 10. 

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