An international team of scientists has detected and confirmed the faintest early-universe galaxy ever -- a finding that can help explain how the "cosmic dark ages" ended.
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Using the WM Keck Observatory on the summit on Mauna Kea in Hawaii, the researchers detected the galaxy as it was 13 billion years ago.
According to Tommaso Treu, professor of physics and astronomy at University of California-Los Angeles, the discovery could be a step toward unraveling one of the biggest mysteries in astronomy -- how a period known as the "cosmic dark ages" ended.
According to the Big Bang theory, the universe cooled as it expanded. As that happened, Treu said, protons captured electrons to form hydrogen atoms, which in turn made the universe opaque to radiation -- giving rise to the cosmic dark ages.
“At some point, a few hundred million years later, the first stars formed and they started to produce ultraviolet light capable of ionizing hydrogen," Treu said.
"Eventually, when there were enough stars, they might have been able to ionize all of the intergalactic hydrogen and create the universe as we see it now,” he added.
That process, called cosmic reionization, happened about 13 billion years ago but scientists have so far been unable to determine whether there were enough stars to do it or whether more exotic sources, like gas falling onto supermassive black holes, might have been responsible.
“Currently, the most likely suspect is stars within faint galaxies that are too faint to see with our telescopes without gravitational lensing magnification," Treu said.
The new study, published in the Astrophysical Journal Letters, exploits gravitational lensing to demonstrate that such galaxies exist, and is thus an important step toward solving this mystery.
Gravitational lensing was first predicted by famous theoretical physicist Albert Einstein.
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The effect is similar to that of an image behind a glass lens appearing distorted because of how the lens bends light.