American Astronomical Society

摘要

Photographers and astronomers love their zoom lenses. Now, a new camera on the Hubble Space Telescope has looked through the best natural lens in space with unprecedented clarity in search of baby galaxies―and has found far fewer than expected. The view comes by means of a "gravitational lens," which arises when light from a distant source passes by a massive object in direct line of sight to Earth. The intervening object's gravity bends and magnifies the source's light. The strongest known lens is Abell 1689, a cluster of galaxies that crams hundreds of times the mass of the Milky Way into a small volume of space more than 2 billion light-years away. Light goes through funhouse-mirror distortions as it traverses the cluster's gravitational dips and bumps. Hubble's recently installed Advanced Camera for Surveys (ACS) targeted Abell 1689 for 13 hours in June 2002, creating an extraordinary map of its eerie arcs and blobs―the imprints of remote galaxies behind Abell 1689.