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Hubble Supernova Discovery Bolsters 'Dark Energy' Theory

April 03, 2001|From Associated Press

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.

"The discovery that the universe is speeding up will be viewed as one of the most important discoveries in all of science in the past 25 years."

A supernova is an exploding star, a cosmic flashbulb. One occurs each second somewhere in space, and that single star beams brighter than the billions of stars in its galaxy combined.

But astronomers have to search mightily for supernovae, making the discovery of a supernova a dramatic event.

Supernova 1997ff exploded more than 10 billion light years from Earth, or 1 1/2 times farther than any previously recorded exploding star, when the universe was a quarter of its current age.

Only recently did the flash reach Hubble. In that way, telescopes act as time machines, allowing astronomers to observe events in the early history of the universe as they are happening.

Cosmologists believe the universe probably was born in an explosion known as the Big Bang 12 billion to 15 billion years ago.

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