Hubble Reopens "Eye" on the Universe and Captures a Cosmic Magnifying Glass

The Hubble telescope reopened its "eye" on the universe following a successful December 1999 servicing mission by imaging a hefty cluster of galaxies, Abell 2218, which acts like a giant zoom lens, magnifying the light of faraway galaxies.

1. What does the picture of Abell 2218 reveal to astronomers?

This "hefty" cluster resides in the constellation Draco, some 2 billion light-years from Earth. The cluster is so massive that its enormous gravitational field deflects light rays passing through it, much as an optical lens bends light to form an image. This phenomenon, called gravitational lensing, magnifies, brightens, and distorts images from faraway objects. The cluster's magnifying powers provide a powerful "zoom lens" for viewing distant galaxies that could not normally be observed with the largest telescopes.

This useful phenomenon has produced the arc-shaped patterns found throughout the Hubble picture. These "arcs" are the distorted images of very distant galaxies, which lie 5 to 10 times farther than the lensing cluster. This distant population existed when the universe was just a quarter of its present age. Through gravitational lensing these remote objects are magnified, enabling scientists to study them in more detail. This analysis provides a direct glimpse of how star-forming regions are distributed in remote galaxies and yields other clues to the early evolution of galaxies.