Hubble's 'zoom lens' probes deeply

The impressive Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope (HST) has used a natural "gravitational lens" far off in space to boost its view of the distant Universe.

The image obtained by the HST offers an unprecedented and dramatic new view of the cosmos, promising to shed light on galaxy evolution and dark matter.

Though gravitational lensing has been studied previously, with Hubble and ground-based telescopes, this phenomenon has never been seen in such detail.

Astronomers will spend months studying the image. Interspersed with the foreground cluster are thousands of galaxies, which are lensed images of the galaxies in the background Universe.

A trillion stars

Hubble peered straight through the centre of one of the most massive known galaxy clusters, Abell 1689. Hubble observed the cluster, located more than 2.2 billion light-years away, for more than 13 hours.

The gravity of the cluster's trillion stars, plus its compliment of mysterious dark matter, acts as a two-million-light-year-wide "lens", bending and magnifying the light of the galaxies located even further away in space.

Although Abell 1689 has been observed by the HST before, the new ACS has revealed remote galaxies previously beyond even Hubble's reach.

Researchers believe that some of them may be twice as faint as those photographed in the Hubble Deep Field image, which previously pushed the telescope to its limits.

New calculations

Astronomers speculate that some of the faintest objects in the picture are over 13 billion light-years away.

In the image, hundreds of these distant galaxies are smeared by the gravitational bending of light into a spider-web tracing of blue and red arcs of light.

The position and extent of the distortion of the smeared galaxies will enable researchers to calculate the amount and the distribution of matter, both visible and dark, in the cluster.

By comparing the amount of estimated matter in the cluster with the amount that can be seen, astronomers hope to gain new information about what the dark matter could be.