January 24, 2000
Photo No: H2000-08
Hubble Opens Its Eye on the Universe & Captures a Cosmic Magnifying Glass
Scanning the heavens for the first time since the successful
December 1999 servicing mission, NASA's Hubble Space Telescope has
imaged a 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. 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.
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. Researchers are
intrigued by a tiny red dot just left of top center. This dot may
be an extremely remote object made visible by the cluster's
magnifying powers. Further investigation is needed to confirm the
The Hubble telescope first viewed this cluster in 1994, producing
one of the most spectacular demonstrations of gravitational lensing
up to that time. Scientists who analyzed that black-and-white
picture discovered more than 50 remote, young galaxies. Hubble's
latest multicolor image of the cluster will allow astronomers to
probe in greater detail the internal structure of these early
galaxies. The color picture already reveals several arc-shaped
features that are embedded in the cluster and cannot be easily
seen in the black-and-white image.
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.
The picture was taken Jan. 11 to 13, 2000, with the Wide Field and
Planetary Camera 2.
Credits: NASA, ESA, Andrew Fruchter (STScI), and the ERO team (STScI)