The Hubble Space Telescope, peering 10 billion years back in time to when the universe was in its adolescence, has spotted the most distant exploding star ever observed.
Researchers said the discovery bolsters the controversial theory that mysterious "dark energy" is accelerating expansion of the cosmos.
Invisible and poorly understood, dark energy might account for as much as two-thirds of space. Proposed a century ago by Einstein, it may counteract more familiar forces such as gravity.
The supernova, barely discernible with the most powerful instruments, provides clues to dark energy. Although dim, the dying star gleams brighter and moves differently than it would if the universe had expanded at a steady rate since the beginning of time.
The Hubble finding is prompting researchers to rethink how the universe works.
Dark energy "is every bit as amazing as black holes," Michael Turner, a University of Chicago cosmologist, said in a briefing at NASA's Washington headquarters. "It controls the density of nature. It's the key to understanding how all of nature's particles and forces fit together.
