Supernovae help gauge power of cosmic lenses

Researchers have said that distant exploding stars observed by NASA's Hubble Space Telescope are providing them with a powerful tool to determine the strength of naturally-occurring "cosmic lenses" that are used to magnify objects in the remote universe.

Two teams of astronomers, working independently, observed three such exploding stars, called supernovae. Their light was amplified by the immense gravity of massive galaxy clusters in the foreground-a phenomenon called gravitational lensing.

Astronomers use the gravitational lensing effect to search for distant objects that might otherwise be too faint to see, even with today's largest telescopes.

Saurabh Jha of Rutgers University in Piscataway, N.J., a member of the Cluster Lensing and Supernova survey with Hubble (CLASH) team, said they have found supernovae that can be used like an eye chart for each lensing cluster.

He said that as they can estimate the intrinsic brightness of the supernovae, we can measure the magnification of the lens.

At least two of the supernovae appear to be a special type of exploding star called Type Ia supernovae, prized by astronomers because they have a consistent level of peak brightness that makes them a reliable tool for estimating distances.

Astronomers from the CLASH team and the Supernova Cosmology Project are using these supernovae in a new method for measuring the magnification, or prescription, of the gravitational lenses.

With these prescriptions, astronomers are now equipped to make increasingly accurate observations of objects in the distant, early universe and better understand the structure of galaxy clusters, including its distribution of dark matter.

The results have been published in The Astrophysical Journal.