Oct. 28, 2007 Exploding stars that light the way for research on
dark energy aren’t as powerful or bright, on average, as they
once were, says a new study by University of Toronto
astronomers. The study, which compared supernovae in nearby
galaxies with those that exploded up to nine billion light years
away in the distant universe, found the distant supernovae were
an average of 12 per cent brighter. The distant supernovae were
brighter because they were younger, the study found. Since
uniformly bright exploding stars help astronomers study the
nature of dark energy – an unknown type of energy that causes
the universe to accelerate its expansion – the team’s findings
suggest it could become more difficult to study dark energy in
the future. Astronomers can correct for supernovae of varying
brightness, but it will prove challenging. “The findings do not
call into question that the universe is accelerating but the
evolving mix of supernovae could limit future attempts to
determine the nature of dark energy,” s