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Hubble Brings Deep Space Into Focus
posted: 10:37 am ET
26 January 2000
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hubble_gravlens_000126 Employing a technique called gravitational lensing, the Hubble Space Telescope used the massive cluster of galaxies called Abell 2218 like a giant zoom lens to magnify the light of more distant galaxies in deep space. 
Photo credit: NASA, ESA, Andrew Fruchter (STScI), and the ERO team Blue pinpoints hot young stars. The yellow-white represents the combined light of many stars in galaxies. Red identifies cool stars, old stars and the glow of distant galaxies. The cluster was imaged in full color, providing astronomers with a spectacular and unique new view of the early universe. "For the first time we can view the internal color structure of some very distant galaxies. This gives us new insight into details of what young galaxies are like," said Richard Ellis at the California Institute of Technology, Pasadena and University of Cambridge, England. "The color of a distant source is preserved by gravitational lensing. By matching images of the same color, families of multiple images produced by the lensing process can be identified." Andrew Fruchter, leader of the team who took the early release observations, is particularly fascinated by an unusual red feature in the field. "This extraordinary object has colors which indicate it is one of two things, either a rare, extremely cool dwarf star in our own galaxy, or one of the most distant objects ever viewed by Hubble, lensed into visibility by the mass of the cluster," Fruchter said. Further observations will be needed to confirm the identity of this unusual object. How gravitational lensing works 
Illustration: Martin Kornmesser & Lars Lindberg Christensen, ST-ECF The light rays (the gray arrows) from the distant galaxy (to the right in the image) are bent when passing a large gathering of mass -- such as the galaxy cluster symbolized by the ball with blue glow in the center. When the light finally arrives at the Earth (to the left), Hubble observes it as coming from a slightly different direction (the red arrow). Note that the shape of the normal-looking spiral galaxy has changed. After passing the large galaxy cluster, there is more than one image, and they are all elongated and bent like bananas. One might say that the cluster has acted like a giant magnifying glass, or gravitational lens, in space -- focusing, magnifying and distorting the images of the galaxy. In addition, the images of some of the lensed galaxies appear red -- the large distance to these galaxies introduce redshift, which shifts their light to the red part of the spectrum.
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