English: The Hubble Space Telescope imaged this giant, cosmic magnifying glass, a massive cluster of galaxies called Abell 2218. 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 provides 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.

The picture is dominated by spiral and elliptical galaxies. Resembling a string of tree lights, the biggest and brightest galaxies are members of the foreground cluster.

The colors in this picture yield clues to the ages, distances, and temperatures of stars, the stuff of galaxies. Blue pinpoints hot, young stars. The yellow-white color of several of the galaxies represents the combined light of many stars. Red identifies cool stars, old stars, and the glow of stars in distant galaxies. This view is only possible by combining Hubble's unique image quality with the rare lensing effect provided by the magnifying cluster.

For more information, visit: hubblesite.org/news_release/news/2000-07

Credit: NASA, Andrew Fruchter (STScI), and the ERO Team [Sylvia Baggett (STScI), Richard Hook (ST-ECF), Zoltan Levay (STScI)]