Posted: Tue, Apr 3, 2001, 1:36 AM ET (0536 GMT)
The most distant supernova yet discovered has provided new evidence that the universe is expanding at an accelerating rate, astronomers said Monday. The supernova, designated 1997ff, was discovered in Hubble Space Telescope images taken in 1997 and 1998 and later determined to be about 11 billion light years from the Earth. The redshift of the supernova matches well with models that predict that the expansion of the universe first slowed, then accelerated as the repulsive force of a mysterious "dark energy" overwhelmed the attractive force of gravity. Astronomers reached that conclusion a few years ago based on observations of closer supernovae, but until now were not able to rule out alternative explanations such as dust or varying brightnesses of supernovae. Left unanswered is an explanation for the dark energy, which may make up 65 percent of the universe: one astrophysicist, calling dark energy "weird stuff", suggested it may be linked to virtual particles in a quantum vacuum or the influence of hidden dimensions predicted by string theory.

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