ASTRONOMERS have begun poring over the deepest ever visible-light image of our early universe, which shows galaxies dating back to only 700 million years after the big bang. Near-infrared images of the same region push it back to within 300 million years of the birth of the universe, but this Ultra Deep Field image is likely to be astronomers’ best visible-light view for many years to come.
To record the image, the Hubble Space Telescope stared at a patch of sky in the constellation Fornax for a total of nearly 12 days. The result shows some 10,000 galaxies sprinkled across an area of sky just a tenth the size of the full moon. The faintest objects are only as bright as a firefly on the moon would be, with just one photon reaching the telescope each minute.
The image reveals normal-looking young galaxies, irregular ones and some objects still to be identified. Looking at one object, Massimo Stiarelli of the Space Telescope Science Institute, Maryland, says, “I have no idea what this is or how it came about.”
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