Ancient faint galaxy uncovers how the ‘cosmic dark ages’ ended
Using a telescope atop Mauna Kea in Hawaii, an international team of scientists has detected the faintest early-universe galaxy ever, according to a report published in Astrophysical Journal Letters.
Seen it as it was 13 billion years ago, the galaxy could help scientists solve one of the greatest mysteries in astronomy: how a period referred to as the “cosmic dark ages” came to an end.
The scientists made the discovery utilizing an effect known as gravitational lensing to see the extremely faint object, which was created right after the Big Bang. First predicted by Albert Einstein nearly a century ago, gravitational lensing has the same effect as a glass lens that distorts an image behind it due to the bending of light.
According to the study, the massive galaxy known as MACS2129.4-0741 created three different images, via gravitational lensing, of the faint galaxy behind it.
Leftovers from the cosmic dark ages
After the Big Bang, the universe cooled and expanded. During this process, protons ensnared electrons to create hydrogen atoms, resulting in the universe becoming opaque to radiation. This began the period known as 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,” study author Tommaso Treu, a professor of physics and astronomy at UCLA, said in a press release. “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.”
That course of action, known as cosmic reionization, occurred approximately 13 billion years ago, but researchers have thus far been incapable of finding out if there were enough stars to do it or if unique sources, like gas falling onto supermassive black holes, may have been the reason.
“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. “This study exploits gravitational lensing to demonstrate that such galaxies exist, and is thus an important step toward solving this mystery.”
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Image credit: Wikimedia Commons
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