Using Powerful Dark Energy Camera, Scientists Reach The Cosmic Dawn

[Judi Lynn]

July 27, 2017


Arizona State University astronomers Sangeeta Malhotra and James Rhoads, working with international teams in Chile and China, have discovered 23 young galaxies, seen as they were 800 million years after the Big Bang. The results from this sample have been recently published in the Astrophysical Journal.

Long ago, about 300,000 years after the beginning of the universe (the Big Bang), the universe was dark. There were no stars or galaxies, and the universe was filled with neutral hydrogen gas. In the next half billion years or so the first galaxies and stars appeared. Their energetic radiation ionized their surroundings, illuminating and transforming the universe.

This dramatic transformation, known as re-ionization, occurred sometime in the interval between 300 million years and one billion years after the Big Bang. Astronomers are trying to pinpoint this milestone more precisely and the galaxies found in this study help in this determination.

“Before re-ionization, these galaxies were very hard to see, because their light is scattered by gas between galaxies, like a car’s headlights in fog,” says Malhotra. “As enough galaxies turn on and ‘burn off the fog’ they become easier to see. By doing so, they help provide a diagnostic to see how much of the ‘fog’ remains at any time in the early universe.”

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