The Hubble eXtreme Deep Field, or XDF, adds another 5,500 galaxies to Hubble's 2003 and 2004 view into a tiny patch of the farthest universe.

Hubble returned to the same target more than 50 times over the past decade, racking up an additional 2 million seconds of exposure time. The most distant objects found date back to about 500 million years after the universe's formation some 13.7 billion years ago.

The early universe was a violent place, filled with colliding and merging galaxies that radiate in bright blue light, a telltale sign of new star formation.

The Hubble portrait also shows brilliantly shining spiral galaxies and older red fuzzy galaxies whose star-formation days are over.

More than 2,000 images of the same field, taken by Hubble's Advanced Camera for Surveys and its near-infrared Wide Field Camera 3, were combined to form the XDF.

"XDF is the deepest image of the sky ever obtained," astronomer Garth Illingworth, with the University of California at Santa Cruz, said in a statement. "It allows us to explore further back in time than ever before.

(Editing by David Adams and Claudia Parsons)

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