Zeroing in on supernova distance

YALE (US)—A new technique for accurately measuring the distances to supernovae may help scientists test predictions about the history of dark energy and its behavior in the early universe.

The team of scientists from Yale University, Lawrence Berkeley National Laboratory, and a consortium of French laboratories began looking for supernovae several years ago with the creation of the Nearby Supernova Factory, the largest supernovae survey ever conducted. To find the exploding stars, the team uses QUEST, the world’s largest optical camera, which was designed and developed at Yale. They have discovered 185 nearby supernovae to date, out of which 58 were analyzed for the current study.

“Measuring the distance to supernovae has been a major problem in astronomy ever since the discovery of dark energy,” says Charles Baltay, Yale’s Eugene Higgins Professor of Physics and one of the paper’s authors. “To understand how dark energy behaved in the early universe, we needed to make more precise measurements.”

Using a telescope in Hawaii to analyze the supernovae’s light signatures, they looked at each star’s individual composition. Providing a custom analysis of its inherent brightness, they were able to determine its distance to better than six percent accuracy.

Next, the team hopes to continue analysis on the remaining nearby supernovae so that they can ultimately test predictions about the history of dark energy.

Type Ia supernovae are exploding stars that made the discovery of dark energy possible in 1998. Astronomers continue to use supernovae to understand the acceleration of the universe’s expansion. In recent years, astronomers have only been able to measure the distances to these “standard candles” to within about 10 percent accuracy, and as such, can only test current models of dark energy to within a certain limit.

These supernovae are so bright that we can see them even when they are billions of light years away. Because supernovae all have roughly the same inherent brightness, astronomers compare this with how bright they appear to be from here on Earth to determine how far away they actually are. Differences in any given star’s composition, however, mean it can be slightly brighter or dimmer when it explodes, which has made extremely precise measurements of their distances difficult.

Reported in May in the journal Astronomy & Astrophysics.

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