LONG BEACH, CALIFORNIA—Buried in this image of a minute patch of the night sky are remote galaxies so faint (marked by diamonds, above) that it took the Hubble Space Telescope more than 100 hours to register their feeble light. Obtained last fall, the Ultra Deep Field 2012 provides astronomers with the deepest view yet of the very early universe. An analysis of the observed properties of the most distant objects, presented here on Monday at the 221st meeting of the American Astronomical Society, indicates that there must be a huge, unobserved population of even fainter galaxies. The energy of newborn stars in these primordial galaxies was responsible for heating up the cold hydrogen gas in intergalactic space, just a few hundred million years after the big bang. Astronomers expect that the future James Webb Space Telescope, due to be launched in 2018, will succeed in actually imaging these faint objects, so stay tuned for an even deeper field.
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