The bright object seen at the center of the image above is a distant galaxy, bigger and more massive than our own Milky Way galaxy. The four fainter images surrounding it are really a single object, called a quasar, that lies behind the galaxy. As the light from the quasar passes the galaxy, its paths get bent by the powerful gravity of the galaxy to form four separate images. Since such bending is like the bending of light passing through an optical lens, the galaxy is called a gravitational lens. Gravitational lenses were discovered in 1979.
Some gravitational lenses distort the light of distant objects into arcs.
Others split it into double, triple, or quadruple images. The first quadruple image to be discovered was dubbed the Einstein Cross in honor of Albert Einstein, who predicted gravitational lensing nearly eighty years ago. The Einstein cross shown above was discovered this past June by Eric Ostrander of Johns Hopkins University. Check out other observations in the Observation of the Week Archive . 1995-1999 TRW Inc.